Faculty Members
Prof. Dr. M. İ. Can Dede
Chair
Educational Background
B.Sc. İstanbul Technical University, Turkey, Mechanical Engineering, 1999
M.Sc. Middle East Technical University, Turkey, Mechanical Engineering, 2003
Ph.D. Florida International University, USA, Mechanical Engineering, 2007
Research Interests
- Haptics
- Teleoperation
- Robot Controller Design
- Unmanned Underwater Vehicles
- +90 232 750 6704 - 6778
- +90 232 750 6701
- Mechanical Engineering Building (Z18)
Publications
2025 |
Görgülü, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gökhan A new safe flexible torsion joint design with softening stiffness characteristics Journal Article 210 , 2025. @article{Görgülü2025, title = {A new safe flexible torsion joint design with softening stiffness characteristics}, author = {Ibrahimcan Görgülü and Mehmet Ismet Can Dede and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-105001995877&doi=10.1016%2fj.mechmachtheory.2025.106015&partnerID=40&md5=cfbbf7366b96aa9e72999c51346475de}, doi = {10.1016/j.mechmachtheory.2025.106015}, year = {2025}, date = {2025-01-01}, volume = {210}, abstract = {This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025 |
Paksoy, Erkan; Dede, Mehmet Ismet Can; Kiper, Gökhan Enhancing trajectory-tracking accuracy of high-acceleration parallel robots by predicting compliant displacements Journal Article 2025. @article{Paksoy2025, title = {Enhancing trajectory-tracking accuracy of high-acceleration parallel robots by predicting compliant displacements}, author = {Erkan Paksoy and Mehmet Ismet Can Dede and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85214919621&doi=10.1017%2fS0263574724002042&partnerID=40&md5=7bf7b46e48dd5459d472e74e623f469a}, doi = {10.1017/S0263574724002042}, year = {2025}, date = {2025-01-01}, abstract = {For precision-required robot operations, the robot's positioning accuracy, repeatability, and stiffness characteristics should be considered. If the mechanism has the desired repeatability performance, a kinematic calibration process can enhance the positioning accuracy. However, for robot operations where high accelerations are needed, the compliance characteristics of the mechanism affect the trajectory-tracking accuracy adversely. In this paper, a novel approach is proposed to enhance the trajectory-tracking accuracy of a robot operating at high accelerations by predicting the compliant displacements when there is no physical contact of the robot with its environment. Also, this case study compares the trajectory-tracking characteristics of an over-constrained and a normal-constrained 2-degrees-of-freedom (DoF) planar parallel mechanism during high-acceleration operations up to 5 g accelerations. In addition, the influence of the end-effector's center of mass (CoM) position along the normal of the plane is investigated in terms of its effects on the proposed trajectory-enhancing algorithm. © The Author(s), 2025. Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } For precision-required robot operations, the robot's positioning accuracy, repeatability, and stiffness characteristics should be considered. If the mechanism has the desired repeatability performance, a kinematic calibration process can enhance the positioning accuracy. However, for robot operations where high accelerations are needed, the compliance characteristics of the mechanism affect the trajectory-tracking accuracy adversely. In this paper, a novel approach is proposed to enhance the trajectory-tracking accuracy of a robot operating at high accelerations by predicting the compliant displacements when there is no physical contact of the robot with its environment. Also, this case study compares the trajectory-tracking characteristics of an over-constrained and a normal-constrained 2-degrees-of-freedom (DoF) planar parallel mechanism during high-acceleration operations up to 5 g accelerations. In addition, the influence of the end-effector's center of mass (CoM) position along the normal of the plane is investigated in terms of its effects on the proposed trajectory-enhancing algorithm. © The Author(s), 2025. Published by Cambridge University Press. |
2024 |
Emet, Hazal; Gür, Berke; Dede, Mehmet İsmet Can The design and kinematic representation of a soft robot in a simulation environment Journal Article Robotica, 42 (1), pp. 139 – 152, 2024. @article{Emet2024139, title = {The design and kinematic representation of a soft robot in a simulation environment}, author = {Hazal Emet and Berke Gür and Mehmet İsmet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85177169148&doi=10.1017%2fS026357472300139X&partnerID=40&md5=9d8bb2595da002ed43f0667f2d03c7f8}, doi = {10.1017/S026357472300139X}, year = {2024}, date = {2024-01-01}, journal = {Robotica}, volume = {42}, number = {1}, pages = {139 – 152}, abstract = {The increase of human presence in the subsea and seabed environments necessitates the development of more capable and highly dexterous, innovative underwater manipulators. Biomimetic soft-robot arms represent a promising candidate for such manipulation systems. However, the well-known modeling techniques and control theories of traditional rigid robots do not apply to soft robots. The challenges of kinematic and dynamic modeling of soft robots with infinite degrees of freedom require the development of dedicated modeling methods. A novel procedure for representing soft-robotic arms and their motion in a rigid-body simulation environment is proposed in this paper. The proposed procedure relies on the piecewise constant curvature approach to simplify the very complex model of hyper-redundant soft-robotic arms, making it suitable for real-time applications. The proposed method is implemented and verified to be used in model-mediated teleoperation of the soft arms of a biomimetic robotic squid designed for underwater manipulation as a case study. © 2023 The Author(s). Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The increase of human presence in the subsea and seabed environments necessitates the development of more capable and highly dexterous, innovative underwater manipulators. Biomimetic soft-robot arms represent a promising candidate for such manipulation systems. However, the well-known modeling techniques and control theories of traditional rigid robots do not apply to soft robots. The challenges of kinematic and dynamic modeling of soft robots with infinite degrees of freedom require the development of dedicated modeling methods. A novel procedure for representing soft-robotic arms and their motion in a rigid-body simulation environment is proposed in this paper. The proposed procedure relies on the piecewise constant curvature approach to simplify the very complex model of hyper-redundant soft-robotic arms, making it suitable for real-time applications. The proposed method is implemented and verified to be used in model-mediated teleoperation of the soft arms of a biomimetic robotic squid designed for underwater manipulation as a case study. © 2023 The Author(s). Published by Cambridge University Press. |
Kucukoglu, Sefa Furkan; Bozelli, Muhammed Rza; Dede, Mehmet Ismet Can Torque-Current Relationship of an MR Brake for Its Open-Loop Control Journal Article 2024. @article{Kucukoglu2024, title = {Torque-Current Relationship of an MR Brake for Its Open-Loop Control}, author = {Sefa Furkan Kucukoglu and Muhammed Rza Bozelli and Mehmet Ismet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85209371077&doi=10.1109%2fTMECH.2024.3487349&partnerID=40&md5=c19ad69a4783f578b77884e9849ba777}, doi = {10.1109/TMECH.2024.3487349}, year = {2024}, date = {2024-01-01}, abstract = {Active and semiactive actuators have been widely preferred for designing an actuation system for kinesthetic-type haptic devices. Among them, magnetorheological fluid-based brakes (MR brakes) offer potent properties, such as high torque/inertia ratio and less power consumption. However, one of the most critical issues to be resolved is their hysteresis behavior. Various methods for modeling the input/output relationship with hysteresis behavior exist. However, hysteresis compensation approaches, i.e., torque-current hysteresis model, are not widely studied for MR Brakes. Therefore, a hysteresis compensation model approach to account for the nonlinear behavior of MR Brake is proposed, and the model is experimentally validated in this article. The model consists of multiple splines and an algorithm that uses these splines in hysteresis compensation. Being relatively simple and easily implementable are the distinguished features of the presented model since an optimization method is not required. Furthermore, the performance of the proposed method is compared with two methods, torque-to-current mapping and inverse Prandtl-Ishlinskii method. The obtained experimental results are investigated with three performance metrics. Finally, the effect of the operational speed on the performance of the hysteresis compensation model is also discussed. © 1996-2012 IEEE.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Active and semiactive actuators have been widely preferred for designing an actuation system for kinesthetic-type haptic devices. Among them, magnetorheological fluid-based brakes (MR brakes) offer potent properties, such as high torque/inertia ratio and less power consumption. However, one of the most critical issues to be resolved is their hysteresis behavior. Various methods for modeling the input/output relationship with hysteresis behavior exist. However, hysteresis compensation approaches, i.e., torque-current hysteresis model, are not widely studied for MR Brakes. Therefore, a hysteresis compensation model approach to account for the nonlinear behavior of MR Brake is proposed, and the model is experimentally validated in this article. The model consists of multiple splines and an algorithm that uses these splines in hysteresis compensation. Being relatively simple and easily implementable are the distinguished features of the presented model since an optimization method is not required. Furthermore, the performance of the proposed method is compared with two methods, torque-to-current mapping and inverse Prandtl-Ishlinskii method. The obtained experimental results are investigated with three performance metrics. Finally, the effect of the operational speed on the performance of the hysteresis compensation model is also discussed. © 1996-2012 IEEE. |
Mobedi, Emir; Dede, Mehmet İsmet Can A Continuously Variable Transmission-Based Variable Stiffness Actuator for pHRI: Design Optimization and Performance Verification Journal Article 16 (8), 2024. @article{Mobedi2024, title = {A Continuously Variable Transmission-Based Variable Stiffness Actuator for pHRI: Design Optimization and Performance Verification}, author = {Emir Mobedi and Mehmet İsmet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85184076584&doi=10.1115%2f1.4064280&partnerID=40&md5=47ac1f5e0bc47eab604d74c470b0ea1f}, doi = {10.1115/1.4064280}, year = {2024}, date = {2024-01-01}, volume = {16}, number = {8}, abstract = {Physical human–robot interfaces (pHRIs) enabled the robots to work alongside the human workers complying with the regulations set for physical human–robot interaction systems. A variety of actuation systems named variable stiffness/impedance actuators (VSAs) are configured to be used in these systems’ design. Recently, we introduced a new continuously variable transmission (CVT) mechanism as an alternative solution in configuring VSAs for pHRI. The optimization of this CVT has significant importance to enhance its application area and to detect the limitations of the system. Thus, in this paper, we present a design optimization approach (an adjustment strategy) for this system based on the design goals, desired force, and minimization of the size of the system. To implement such design goals, the static force analysis of the CVT is performed and validated. Furthermore, the fabrication of the optimized prototype is presented, and the experimental verification is performed considering the requirements of VSAs: independent position and stiffness variation, and shock absorbing. Finally, the system is calibrated to display 6 N continuous output force throughout its transmission variation range. © 2024 by ASME.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Physical human–robot interfaces (pHRIs) enabled the robots to work alongside the human workers complying with the regulations set for physical human–robot interaction systems. A variety of actuation systems named variable stiffness/impedance actuators (VSAs) are configured to be used in these systems’ design. Recently, we introduced a new continuously variable transmission (CVT) mechanism as an alternative solution in configuring VSAs for pHRI. The optimization of this CVT has significant importance to enhance its application area and to detect the limitations of the system. Thus, in this paper, we present a design optimization approach (an adjustment strategy) for this system based on the design goals, desired force, and minimization of the size of the system. To implement such design goals, the static force analysis of the CVT is performed and validated. Furthermore, the fabrication of the optimized prototype is presented, and the experimental verification is performed considering the requirements of VSAs: independent position and stiffness variation, and shock absorbing. Finally, the system is calibrated to display 6 N continuous output force throughout its transmission variation range. © 2024 by ASME. |
2023 |
Gorgulu, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gokhan Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism Journal Article MECHANISM AND MACHINE THEORY, 185 , 2023. @article{WOS:000966404700001, title = {Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism}, author = {Ibrahimcan Gorgulu and Mehmet Ismet Can Dede and Gokhan Kiper}, doi = {10.1016/j.mechmachtheory.2023.105343}, year = {2023}, date = {2023-07-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {185}, abstract = {Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results. |
Aldanmaz, Ataol Behram; Ayit, Orhan; Kiper, Gökhan; Dede, Mehmet İsmet Can Gravity compensation of a 2R1T mechanism with remote center of motion for minimally invasive transnasal surgery applications Journal Article Robotica, 41 (3), pp. 807 – 820, 2023, (All Open Access, Green Open Access). @article{Aldanmaz2023807, title = {Gravity compensation of a 2R1T mechanism with remote center of motion for minimally invasive transnasal surgery applications}, author = {Ataol Behram Aldanmaz and Orhan Ayit and Gökhan Kiper and Mehmet İsmet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85148022623&doi=10.1017%2fS0263574722000534&partnerID=40&md5=d9e00d3ba2c7864df127963817903586}, doi = {10.1017/S0263574722000534}, year = {2023}, date = {2023-01-01}, journal = {Robotica}, volume = {41}, number = {3}, pages = {807 – 820}, abstract = {This work addresses the gravity balancing of a 2R1T (2 rotations - 1 translation) mechanism with remote center of motion. A previously developed balancing solution is modified and applied to a prototype, and test results are presented. The mechanism is an endoscope holder for minimally invasive transnasal pituitary gland surgery. In this surgery, the endoscope is inserted through a nostril of the patient through a natural path to the pituitary gland. During the surgery, it is vital for the manipulator to be statically balanced so that in case of a motor failure, the patient is protected against any harmful motion of the endoscope. Additionally, static balancing takes the gravitational load from the actuators and hence facilitates the control of the mechanism. The mechanism is a 2URRR-URR type parallel manipulator with three legs. The payload mass is distributed to the legs on the sides. By using counter-masses for two links of each leg, the center of mass of each leg is lumped on the proximal link which simplifies the problem of balancing of a two degree-of-freedom inverted pendulum. The two proximal links with the lumped mass are statically balanced via springs. Dynamic simulations indicate that when the mechanism is statically balanced, generated actuator torques are reduced by 93.5%. Finally, the balancing solution is implemented on the prototype of the manipulator. The tests indicate that the manipulator is statically balanced within its task space when the actuators are disconnected. When the actuators are connected, the torque requirements decrease by about 37.8% with balancing. © The Author(s), 2022. Published by Cambridge University Press.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } This work addresses the gravity balancing of a 2R1T (2 rotations - 1 translation) mechanism with remote center of motion. A previously developed balancing solution is modified and applied to a prototype, and test results are presented. The mechanism is an endoscope holder for minimally invasive transnasal pituitary gland surgery. In this surgery, the endoscope is inserted through a nostril of the patient through a natural path to the pituitary gland. During the surgery, it is vital for the manipulator to be statically balanced so that in case of a motor failure, the patient is protected against any harmful motion of the endoscope. Additionally, static balancing takes the gravitational load from the actuators and hence facilitates the control of the mechanism. The mechanism is a 2URRR-URR type parallel manipulator with three legs. The payload mass is distributed to the legs on the sides. By using counter-masses for two links of each leg, the center of mass of each leg is lumped on the proximal link which simplifies the problem of balancing of a two degree-of-freedom inverted pendulum. The two proximal links with the lumped mass are statically balanced via springs. Dynamic simulations indicate that when the mechanism is statically balanced, generated actuator torques are reduced by 93.5%. Finally, the balancing solution is implemented on the prototype of the manipulator. The tests indicate that the manipulator is statically balanced within its task space when the actuators are disconnected. When the actuators are connected, the torque requirements decrease by about 37.8% with balancing. © The Author(s), 2022. Published by Cambridge University Press. |
Dede, Mehmet İsmet Can; Büyüköztekin, Tarlk; Hanalioǧlu, Şahin; Işlkay, İlkay; Berker, Mustafa Enabling personalization of a robotic surgery procedure via a surgery training simulator Journal Article Robotica, 41 (3), pp. 869 – 884, 2023. @article{Dede2023869, title = {Enabling personalization of a robotic surgery procedure via a surgery training simulator}, author = {Mehmet İsmet Can Dede and Tarlk Büyüköztekin and Şahin Hanalioǧlu and İlkay Işlkay and Mustafa Berker}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85148013607&doi=10.1017%2fS0263574722001023&partnerID=40&md5=2ca0aadba08af765e6eb072301e16eaa}, doi = {10.1017/S0263574722001023}, year = {2023}, date = {2023-01-01}, journal = {Robotica}, volume = {41}, number = {3}, pages = {869 – 884}, abstract = {Although robotic or robot-assisted surgery has been increasingly used by many surgical disciplines, its application in cranial or skull base surgery is still in its infancy. Master-slave teleoperation setting of these robotic systems enables these surgical procedures to be replicated in a virtual reality environment for surgeon training purposes. A variety of teleoperation modes were previously determined with respect to the motion capability of the surgeon's hand that wears the ring as the surgeon handles a surgical tool inside the surgical workspace. In this surgery training simulator developed for a robot-assisted endoscopic skull base surgery, a new strategy is developed to identify the preferred motion axes of the surgeon. This simulator is designed specifically for tuning the teleoperation system for each surgeon via the identification. This tuning capability brings flexibility to adjust the system operation with respect to the motion characteristics of the surgeon. © The Author(s), 2022. Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Although robotic or robot-assisted surgery has been increasingly used by many surgical disciplines, its application in cranial or skull base surgery is still in its infancy. Master-slave teleoperation setting of these robotic systems enables these surgical procedures to be replicated in a virtual reality environment for surgeon training purposes. A variety of teleoperation modes were previously determined with respect to the motion capability of the surgeon's hand that wears the ring as the surgeon handles a surgical tool inside the surgical workspace. In this surgery training simulator developed for a robot-assisted endoscopic skull base surgery, a new strategy is developed to identify the preferred motion axes of the surgeon. This simulator is designed specifically for tuning the teleoperation system for each surgeon via the identification. This tuning capability brings flexibility to adjust the system operation with respect to the motion characteristics of the surgeon. © The Author(s), 2022. Published by Cambridge University Press. |
Ayit, Orhan; Dede, Mehmet İsmet Can A study on a computationally efficient controller design for a surgical robotic system Journal Article International Journal of Dynamics and Control, 11 (6), pp. 3176 – 3187, 2023. @article{Ayit20233176, title = {A study on a computationally efficient controller design for a surgical robotic system}, author = {Orhan Ayit and Mehmet İsmet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85153031240&doi=10.1007%2fs40435-023-01164-y&partnerID=40&md5=cdb5797de4d939164cc1a564579d738c}, doi = {10.1007/s40435-023-01164-y}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Dynamics and Control}, volume = {11}, number = {6}, pages = {3176 – 3187}, abstract = {The control algorithms of the surgical robotic system using the robot’s dynamics produce a relatively high computational load on the processor. This paper develops a computationally efficient computed torque controller by using a simplified dynamic modeling method and implemented in a novel surgical robot experimentally. In addition, an independent joint controller is designed and implemented to compare the results of the computed torque controller. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The control algorithms of the surgical robotic system using the robot’s dynamics produce a relatively high computational load on the processor. This paper develops a computationally efficient computed torque controller by using a simplified dynamic modeling method and implemented in a novel surgical robot experimentally. In addition, an independent joint controller is designed and implemented to compare the results of the computed torque controller. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature. |
2017 |
Uzunoglu, Emre; Dede, Mehmet Ismet Can Extending model-mediation method to multi-degree-of-freedom teleoperation systems experiencing time delays in communication Journal Article ROBOTICA, 35 (5), pp. 1121-1136, 2017, ISSN: 0263-5747. @article{ISI:000399043500007, title = {Extending model-mediation method to multi-degree-of-freedom teleoperation systems experiencing time delays in communication}, author = {Emre Uzunoglu and Mehmet Ismet Can Dede}, doi = {10.1017/S0263574715001010}, issn = {0263-5747}, year = {2017}, date = {2017-05-01}, journal = {ROBOTICA}, volume = {35}, number = {5}, pages = {1121-1136}, abstract = {In this study, a bilateral teleoperation control algorithm is developed in which the model-mediation method is integrated with an impedance controller. The model-mediation method is also extended to three-degrees-of-freedom teleoperation. The aim of this controller is to compensate for instability issues and excessive forcing applied to the slave environment stemming from time delays in communication. The proposed control method is experimentally tested with two haptic desktop devices. Test results indicate that stability and passivity of the bilateral teleoperation system is preserved under variable time delays in communication. It is also observed that safer interactions of the slave system with its environment can be achieved by utilizing an extended version of the model-mediation method with an impedance controller.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a bilateral teleoperation control algorithm is developed in which the model-mediation method is integrated with an impedance controller. The model-mediation method is also extended to three-degrees-of-freedom teleoperation. The aim of this controller is to compensate for instability issues and excessive forcing applied to the slave environment stemming from time delays in communication. The proposed control method is experimentally tested with two haptic desktop devices. Test results indicate that stability and passivity of the bilateral teleoperation system is preserved under variable time delays in communication. It is also observed that safer interactions of the slave system with its environment can be achieved by utilizing an extended version of the model-mediation method with an impedance controller. |
Kiper, Gokhan; Dede, Mehmet Ismet Can; Maaroof, Omar W; Ozkahya, Merve Function generation with two loop mechanisms using decomposition and correction method Journal Article MECHANISM AND MACHINE THEORY, 110 , pp. 16-26, 2017, ISSN: 0094-114X. @article{ISI:000394063500002, title = {Function generation with two loop mechanisms using decomposition and correction method}, author = {Gokhan Kiper and Mehmet Ismet Can Dede and Omar W Maaroof and Merve Ozkahya}, doi = {10.1016/j.mechmachtheory.2016.12.004}, issn = {0094-114X}, year = {2017}, date = {2017-04-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {110}, pages = {16-26}, abstract = {Method of decomposition has been successfully applied to function generation with multi-loop mechanisms. For a two-loop mechanism, a function y = f(x) can be decomposed into two as w = g(x) and y = h(w) = h(g(x)) = f(x). This study makes use of the method of decomposition for two loop mechanisms, where the errors from each loop are forced to match each other. In the first loop, which includes the input of the mechanism, the decomposed function (g) is generated and the resulting structural error is determined. Then, for the second loop, the desired output of the function (f) is considered as an input and the structural error of the decomposed function (g) is determined. By matching the obtained structural errors, the final error in the output of the mechanism is reduced. Three different correction methods are proposed. The first method has three precision points per loop, while the second method has four. In the third method, the extrema of the errors from both loops are matched. The methods are applied to a Watt II type planar six-bar linkage for demonstration. Several numerical examples are worked out and the results are compared with the results in the literature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Method of decomposition has been successfully applied to function generation with multi-loop mechanisms. For a two-loop mechanism, a function y = f(x) can be decomposed into two as w = g(x) and y = h(w) = h(g(x)) = f(x). This study makes use of the method of decomposition for two loop mechanisms, where the errors from each loop are forced to match each other. In the first loop, which includes the input of the mechanism, the decomposed function (g) is generated and the resulting structural error is determined. Then, for the second loop, the desired output of the function (f) is considered as an input and the structural error of the decomposed function (g) is determined. By matching the obtained structural errors, the final error in the output of the mechanism is reduced. Three different correction methods are proposed. The first method has three precision points per loop, while the second method has four. In the third method, the extrema of the errors from both loops are matched. The methods are applied to a Watt II type planar six-bar linkage for demonstration. Several numerical examples are worked out and the results are compared with the results in the literature. |
2016 |
Gundogdu, Hilal Tolasa; Dede, Mehmet Ismet Can; Taner, Baris; Ridolfi, Alessandro; Costanzi, Riccardo; Allotta, Benedetto Design and testing of an innovative cleaning tool for underwater applications Journal Article PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART M-JOURNAL OF ENGINEERING FOR THE MARITIME ENVIRONMENT, 230 (4), pp. 579-590, 2016, ISSN: 1475-0902. @article{ISI:000392916800003, title = {Design and testing of an innovative cleaning tool for underwater applications}, author = {Hilal Tolasa Gundogdu and Mehmet Ismet Can Dede and Baris Taner and Alessandro Ridolfi and Riccardo Costanzi and Benedetto Allotta}, doi = {10.1177/1475090215610599}, issn = {1475-0902}, year = {2016}, date = {2016-11-01}, journal = {PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART M-JOURNAL OF ENGINEERING FOR THE MARITIME ENVIRONMENT}, volume = {230}, number = {4}, pages = {579-590}, abstract = {The aim of this work is to describe the development of an innovative cleaning tool for underwater applications, to be used in particular in the field of underwater archaeology. This work takes place in the framework of the EU FP7-funded ARROWS project. ARROWS adapts and develops low-cost autonomous underwater vehicle technologies to significantly reduce the costs of underwater archaeological operations, covering the full extent of archaeological campaigns. The project deals with underwater mapping, diagnosis and cleaning tasks. During the first half of the project, a cleaning tool prototype, able to be mounted on underwater vehicles, has been worked out: this cleaning tool will be exploited not only during research missions but also for the periodic monitoring, controlling and maintenance activities of well-known underwater archaeological sites (e.g. periodic cleaning operations).}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this work is to describe the development of an innovative cleaning tool for underwater applications, to be used in particular in the field of underwater archaeology. This work takes place in the framework of the EU FP7-funded ARROWS project. ARROWS adapts and develops low-cost autonomous underwater vehicle technologies to significantly reduce the costs of underwater archaeological operations, covering the full extent of archaeological campaigns. The project deals with underwater mapping, diagnosis and cleaning tasks. During the first half of the project, a cleaning tool prototype, able to be mounted on underwater vehicles, has been worked out: this cleaning tool will be exploited not only during research missions but also for the periodic monitoring, controlling and maintenance activities of well-known underwater archaeological sites (e.g. periodic cleaning operations). |
Dede, Mehmet Ismet Can; Maaroof, Omar W; Tatlicioglu, Enver A New Objective Function for Obstacle Avoidance by Redundant Service Robot Arms Journal Article INTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS, 13 , 2016, ISSN: 1729-8806. @article{ISI:000372038700001, title = {A New Objective Function for Obstacle Avoidance by Redundant Service Robot Arms}, author = {Mehmet Ismet Can Dede and Omar W Maaroof and Enver Tatlicioglu}, doi = {10.5772/62471}, issn = {1729-8806}, year = {2016}, date = {2016-03-01}, journal = {INTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS}, volume = {13}, abstract = {The performance of task-space tracking control of kinematically redundant robots regulating self-motion to ensure obstacle avoidance is studied and discussed. As the sub-task objective, the links of the kinematically redundant assistive robot should avoid any collisions with the patient that is being assisted. The shortcomings of the obstacle avoidance algorithms are discussed and a new obstacle avoidance algorithm is proposed. The performance of the proposed algorithm is validated with tests that were carried out using the virtual model of a seven degrees-of-freedom robot arm. The test results indicate that the developed controller for the robot manipulator is successful in both accomplishing the main-task and the sub-task objectives.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The performance of task-space tracking control of kinematically redundant robots regulating self-motion to ensure obstacle avoidance is studied and discussed. As the sub-task objective, the links of the kinematically redundant assistive robot should avoid any collisions with the patient that is being assisted. The shortcomings of the obstacle avoidance algorithms are discussed and a new obstacle avoidance algorithm is proposed. The performance of the proposed algorithm is validated with tests that were carried out using the virtual model of a seven degrees-of-freedom robot arm. The test results indicate that the developed controller for the robot manipulator is successful in both accomplishing the main-task and the sub-task objectives. |
Uzunoglu, Emre; Dede, Mehmet Ismet Can; Kiper, Gokhan Trajectory planning for a planar macro-micro manipulator of a laser-cutting machine Journal Article INDUSTRIAL ROBOT-THE INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH AND APPLICATION, 43 (5, SI), pp. 513-523, 2016, ISSN: 0143-991X. @article{ISI:000386142100009, title = {Trajectory planning for a planar macro-micro manipulator of a laser-cutting machine}, author = {Emre Uzunoglu and Mehmet Ismet Can Dede and Gokhan Kiper}, doi = {10.1108/IR-02-2016-0057}, issn = {0143-991X}, year = {2016}, date = {2016-01-01}, journal = {INDUSTRIAL ROBOT-THE INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH AND APPLICATION}, volume = {43}, number = {5, SI}, pages = {513-523}, abstract = {Purpose - In the industry, there is always a demand to shorten the task completion durations to maximize the efficiency of the operation. This work focuses on making use of a special type of kinematic redundancy, macro-micro manipulation, to minimize the task completion duration. The purpose of this paper is to develop the most convenient trajectory planner to be integrated with industrial computerized numerical control (CNC) systems to resolve kinematic redundancy for task duration minimization. Design/methodology/approach - A special type of kinematic redundancy is devised by using two kinematically different mechanisms that have different advantages, which are named as macro and micro mechanisms. In this case, the control design including the trajectory planning should be devised taking into account the distinct advantages of both mechanisms. A new trajectory planning algorithm is designed and used for the constructed planar laser-cutting machine, and some benchmark pieces are cut. Findings - Offline method has practical limitations for employment in a real case scenario such as assuming infinite jerk limits for each axis motion. This limitation was removed by using an online trajectory generation technique. Experimental test results indicate that the online trajectory planning technique developed for the macro-micro mechanism to shorten the task duration was successful. Practical implications - Although the new trajectory planning algorithm is implemented for a laser-cutting machine, it can also be used for other manufacturing systems that require higher acceleration and accuracy levels than the conventional machines. The new algorithm is compatible with the commercially available CNC systems. Originality/value - In this work, a new approach to reducing the task duration for planar machining operations was introduced by making use of macro-micro manipulation concept. The core novelty of the work is devising trajectory planning algorithms to get the most efficiency in terms of acceleration limits from a macro-micro manipulation while making these algorithms deployable to most of the CNC systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Purpose - In the industry, there is always a demand to shorten the task completion durations to maximize the efficiency of the operation. This work focuses on making use of a special type of kinematic redundancy, macro-micro manipulation, to minimize the task completion duration. The purpose of this paper is to develop the most convenient trajectory planner to be integrated with industrial computerized numerical control (CNC) systems to resolve kinematic redundancy for task duration minimization. Design/methodology/approach - A special type of kinematic redundancy is devised by using two kinematically different mechanisms that have different advantages, which are named as macro and micro mechanisms. In this case, the control design including the trajectory planning should be devised taking into account the distinct advantages of both mechanisms. A new trajectory planning algorithm is designed and used for the constructed planar laser-cutting machine, and some benchmark pieces are cut. Findings - Offline method has practical limitations for employment in a real case scenario such as assuming infinite jerk limits for each axis motion. This limitation was removed by using an online trajectory generation technique. Experimental test results indicate that the online trajectory planning technique developed for the macro-micro mechanism to shorten the task duration was successful. Practical implications - Although the new trajectory planning algorithm is implemented for a laser-cutting machine, it can also be used for other manufacturing systems that require higher acceleration and accuracy levels than the conventional machines. The new algorithm is compatible with the commercially available CNC systems. Originality/value - In this work, a new approach to reducing the task duration for planar machining operations was introduced by making use of macro-micro manipulation concept. The core novelty of the work is devising trajectory planning algorithms to get the most efficiency in terms of acceleration limits from a macro-micro manipulation while making these algorithms deployable to most of the CNC systems. |
2014 |
Maaroof, Omar W; Dede, Mehmet Ismet Can Kinematic synthesis of over-constrained double-spherical six-bar mechanism Journal Article MECHANISM AND MACHINE THEORY, 73 , pp. 154-168, 2014, ISSN: 0094-114X. @article{ISI:000332399300011, title = {Kinematic synthesis of over-constrained double-spherical six-bar mechanism}, author = {Omar W Maaroof and Mehmet Ismet Can Dede}, doi = {10.1016/j.mechmachtheory.2013.10.013}, issn = {0094-114X}, year = {2014}, date = {2014-03-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {73}, pages = {154-168}, abstract = {The main problem in the synthesis of any mechanism is the fact that the objective function of the mechanism, which will be synthesized, should be found and simplified by using appropriate algebraic method. Finding objective function and calculation process can become complicated especially when the number of design parameters is increased for the over-constrained mechanisms. A new technique for solving the kinematic synthesis of over-constrained double-spherical six-bar mechanism is developed and applied in this work. Interpolation approximation is used during synthesis procedure. A numerical example for the kinematic synthesis procedure is given to validate the theory in application. (C) 2013 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The main problem in the synthesis of any mechanism is the fact that the objective function of the mechanism, which will be synthesized, should be found and simplified by using appropriate algebraic method. Finding objective function and calculation process can become complicated especially when the number of design parameters is increased for the over-constrained mechanisms. A new technique for solving the kinematic synthesis of over-constrained double-spherical six-bar mechanism is developed and applied in this work. Interpolation approximation is used during synthesis procedure. A numerical example for the kinematic synthesis procedure is given to validate the theory in application. (C) 2013 Elsevier Ltd. All rights reserved. |
2013 |
Kiper, Gökhan; Bilgincan, Tunç; Dede, Mehmet İsmet Can Function generation synthesis of planar 5R mechanism Journal Article 2013. @article{kiper2013function, title = {Function generation synthesis of planar 5R mechanism}, author = {Gökhan Kiper and Tunç Bilgincan and Mehmet İsmet Can Dede}, url = {http://hdl.handle.net/11147/4217}, year = {2013}, date = {2013-01-01}, publisher = {IFToMM}, abstract = {This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined. |
Prof. Dr. H. Seçil Artem
External Transfer Coordinator
Educational Background
B.Sc. Middle East Technical University, Turkey, Engineering Sciences, 1987
M.Sc. Middle East Technical University, Turkey, Engineering Sciences, 1990
Ph.D. Middle East Technical University, Turkey, Engineering Sciences, 1999
Research Interests
- Engineering Mathematics
- Numerical solutions for PDEs
- +90 232 750 6771
- +90 232 750 6701
- Mechanical Engineering Building (114)
Publications
2025 |
Ayakdas, Ozan; Artem, Seçil H; Savran, Melih; Aydin, Levent; Adali, Sarp 354 , 2025. @article{Ayakdas2025, title = {Vibration analysis and optimal design of multiscale hybrid flax fiber/graphene nanoplatelets reinforced laminates using modified differential evolution algorithm}, author = {Ozan Ayakdas and H Seçil Artem and Melih Savran and Levent Aydin and Sarp Adali}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85213543074&doi=10.1016%2fj.compstruct.2024.118804&partnerID=40&md5=7209be34320ef2e6b6d9cc3ad7b80ec4}, doi = {10.1016/j.compstruct.2024.118804}, year = {2025}, date = {2025-01-01}, volume = {354}, abstract = {One of the relatively recent developments in composites is using different material combinations and nano-scale reinforcements such as Graphene Nanoplatelets (GPLs) to develop hybrid fiber composites. A further development is the use of natural flax fiber in composites in response to a growing demand over the past few decades for affordable, lightweight, and environmentally-friendly materials. In order to meet this growing demand, in the present study composites based on graphene nanoplatelets and flax fibers are investigated considering their weight, cost, and natural frequency implications. Furthermore, the Modified Differential Evolution (MDE) algorithm is implemented for the optimum design problems involving the stacking sequences and weight fractions of GPLs in each layer. For the optimal design problems, natural frequency is defined as the objective function with the design variables specified as the orientations of flax fibers and the weight contents of GPLs in each layer. The effective material properties are computed based on Halpin-Tsai and the rule of mixture formulations. Navier solution approach is implemented to solve the eigenvalue problems with the stiffness matrix based on the First-order Shear Deformation Theory (FSDT). Optimal designs based on flax fibers, optimal GPL contents, and stacking sequences lead to efficient and environmentally-friendly composite plates. Optimum multiscale hybrid nanocomposite designs include high natural frequency, light weight, and cost-effectiveness compared to conventional carbon and glass fibers reinforced equivalents. © 2024 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } One of the relatively recent developments in composites is using different material combinations and nano-scale reinforcements such as Graphene Nanoplatelets (GPLs) to develop hybrid fiber composites. A further development is the use of natural flax fiber in composites in response to a growing demand over the past few decades for affordable, lightweight, and environmentally-friendly materials. In order to meet this growing demand, in the present study composites based on graphene nanoplatelets and flax fibers are investigated considering their weight, cost, and natural frequency implications. Furthermore, the Modified Differential Evolution (MDE) algorithm is implemented for the optimum design problems involving the stacking sequences and weight fractions of GPLs in each layer. For the optimal design problems, natural frequency is defined as the objective function with the design variables specified as the orientations of flax fibers and the weight contents of GPLs in each layer. The effective material properties are computed based on Halpin-Tsai and the rule of mixture formulations. Navier solution approach is implemented to solve the eigenvalue problems with the stiffness matrix based on the First-order Shear Deformation Theory (FSDT). Optimal designs based on flax fibers, optimal GPL contents, and stacking sequences lead to efficient and environmentally-friendly composite plates. Optimum multiscale hybrid nanocomposite designs include high natural frequency, light weight, and cost-effectiveness compared to conventional carbon and glass fibers reinforced equivalents. © 2024 Elsevier Ltd |
2024 |
Deveci, Hamza Arda; Artem, Hatice Seçil; Güneş, Mehmet Deniz; Tanoğlu, Metin 2024. @article{Deveci2024, title = {Fatigue-resistant design of carbon/epoxy composites based on a failure tensor polynomial model by particle swarm optimization-sequential quadratic programming algorithm}, author = {Hamza Arda Deveci and Hatice Seçil Artem and Mehmet Deniz Güneş and Metin Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85194821289&doi=10.1177%2f07316844241256815&partnerID=40&md5=1247ee8142b1887155d747393102dd2b}, doi = {10.1177/07316844241256815}, year = {2024}, date = {2024-01-01}, abstract = {This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024. |
Deveci, Hamza Arda; Artem, Hatice Seçil; Güneş, Mehmet Deniz; Tanoğlu, Metin 2024. @article{Deveci2024b, title = {Fatigue-resistant design of carbon/epoxy composites based on a failure tensor polynomial model by particle swarm optimization-sequential quadratic programming algorithm}, author = {Hamza Arda Deveci and Hatice Seçil Artem and Mehmet Deniz Güneş and Metin Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85194821289&doi=10.1177%2f07316844241256815&partnerID=40&md5=1247ee8142b1887155d747393102dd2b}, doi = {10.1177/07316844241256815}, year = {2024}, date = {2024-01-01}, abstract = {This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024. |
2021 |
Kangal, Serkan; Say, Harun A; Ayakda, Ozan; Kartav, Osman; Aydin, Levent; Artem, Secil H; Aktas, Engin; Yuceturk, Kutay; Tanoglu, Metin; Kandemir, Sinan; Beylergil, Bertan A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels Journal Article JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, 143 (4), 2021. @article{WOS:000669955100012, title = {A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels}, author = {Serkan Kangal and Harun A Say and Ozan Ayakda and Osman Kartav and Levent Aydin and Secil H Artem and Engin Aktas and Kutay Yuceturk and Metin Tanoglu and Sinan Kandemir and Bertan Beylergil}, doi = {10.1115/1.4049644}, year = {2021}, date = {2021-08-01}, journal = {JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, volume = {143}, number = {4}, abstract = {This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis. |
2017 |
Deveci, Arda H; Artem, Secil H Optimum design of fatigue-resistant composite laminates using hybrid algorithm Journal Article COMPOSITE STRUCTURES, 168 , pp. 178-188, 2017, ISSN: 0263-8223. @article{ISI:000398014200017, title = {Optimum design of fatigue-resistant composite laminates using hybrid algorithm}, author = {Arda H Deveci and Secil H Artem}, doi = {10.1016/j.compstruct.2017.01.064}, issn = {0263-8223}, year = {2017}, date = {2017-05-01}, journal = {COMPOSITE STRUCTURES}, volume = {168}, pages = {178-188}, abstract = {In this study, a fatigue life prediction model termed as Failure Tensor Polynomial in Fatigue (FTPF) is applied to the optimum stacking sequence design of laminated composites under various in-plane cyclic loadings to obtain maximum fatigue life. The validity of the model is investigated with an experimental correlation using the data available in the literature. The correlation study indicates the reliability of FTPF, and its applicability to different composite materials and multidirectional laminates. In the optimization, a hybrid algorithm combining genetic algorithm and generalized pattern search algorithm is used. It is found by test problems that the hybrid algorithm shows superior performance in finding global optima compared to the so far best results in the literature. After the verifications, a number of problems including different design cases are solved, and the optimum designs constituted of discrete fiber angles which give the maximum possible fatigue lives are proposed to discuss. A comparison study is also performed with selected design cases to demonstrate potential advantages of using non-conventional fiber angles in design. (C) 2017 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a fatigue life prediction model termed as Failure Tensor Polynomial in Fatigue (FTPF) is applied to the optimum stacking sequence design of laminated composites under various in-plane cyclic loadings to obtain maximum fatigue life. The validity of the model is investigated with an experimental correlation using the data available in the literature. The correlation study indicates the reliability of FTPF, and its applicability to different composite materials and multidirectional laminates. In the optimization, a hybrid algorithm combining genetic algorithm and generalized pattern search algorithm is used. It is found by test problems that the hybrid algorithm shows superior performance in finding global optima compared to the so far best results in the literature. After the verifications, a number of problems including different design cases are solved, and the optimum designs constituted of discrete fiber angles which give the maximum possible fatigue lives are proposed to discuss. A comparison study is also performed with selected design cases to demonstrate potential advantages of using non-conventional fiber angles in design. (C) 2017 Elsevier Ltd. All rights reserved. |
2016 |
Deveci, Arda H; Aydin, Levent; Artem, Secil H Buckling optimization of composite laminates using a hybrid algorithm under Puck failure criterion constraint Journal Article JOURNAL OF REINFORCED PLASTICS AND COMPOSITES, 35 (16), pp. 1233-1247, 2016, ISSN: 0731-6844. @article{ISI:000382493000002, title = {Buckling optimization of composite laminates using a hybrid algorithm under Puck failure criterion constraint}, author = {Arda H Deveci and Levent Aydin and Secil H Artem}, doi = {10.1177/0731684416646860}, issn = {0731-6844}, year = {2016}, date = {2016-08-01}, journal = {JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, volume = {35}, number = {16}, pages = {1233-1247}, abstract = {In this study, an optimization procedure is proposed to find the optimum stacking sequence designs of laminated composite plates in different fiber angle domains for maximum buckling resistance. A hybrid algorithm combining genetic algorithm and trust region reflective algorithm is used in the optimization to obtain higher performance and improve the quality of solutions. As a novelty, Puck fiber and inter-fiber failure criteria are directly implemented to the optimization problems as nonlinear function constraints, which have allowed more consistent and feasible results. The performance of the hybrid algorithm is demonstrated by comparing with the individual performances of genetic and trust region reflective algorithms via test problems from the literature. Also, a study is performed to exhibit the effectiveness of the selected failure criterion as constraint among the other common criteria. The proposed procedure is used to solve many problems including various design considerations. The results indicate that reliable stacking sequence designs can be achieved in specific configurations even for the composite plates subjected to superior buckling loads when Puck physically based (3D) failure theory is considered as a first ply failure constraint in the buckling optimization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, an optimization procedure is proposed to find the optimum stacking sequence designs of laminated composite plates in different fiber angle domains for maximum buckling resistance. A hybrid algorithm combining genetic algorithm and trust region reflective algorithm is used in the optimization to obtain higher performance and improve the quality of solutions. As a novelty, Puck fiber and inter-fiber failure criteria are directly implemented to the optimization problems as nonlinear function constraints, which have allowed more consistent and feasible results. The performance of the hybrid algorithm is demonstrated by comparing with the individual performances of genetic and trust region reflective algorithms via test problems from the literature. Also, a study is performed to exhibit the effectiveness of the selected failure criterion as constraint among the other common criteria. The proposed procedure is used to solve many problems including various design considerations. The results indicate that reliable stacking sequence designs can be achieved in specific configurations even for the composite plates subjected to superior buckling loads when Puck physically based (3D) failure theory is considered as a first ply failure constraint in the buckling optimization. |
2008 |
Aydin, Levent; Artem, Secil Altundag H Axisymmetric crack problem of thick-walled cylinder with loadings on crack surfaces Journal Article ENGINEERING FRACTURE MECHANICS, 75 (6), pp. 1294-1309, 2008, ISSN: 0013-7944. @article{ISI:000253751900002, title = {Axisymmetric crack problem of thick-walled cylinder with loadings on crack surfaces}, author = {Levent Aydin and Secil Altundag H Artem}, doi = {10.1016/j.engfracmech.2007.07.016}, issn = {0013-7944}, year = {2008}, date = {2008-04-01}, journal = {ENGINEERING FRACTURE MECHANICS}, volume = {75}, number = {6}, pages = {1294-1309}, abstract = {This study is concerned with the fracture of an infinite thick-walled cylinder. The inner surface of the cylinder is stress free and the outer is rigidly fixed. The cylinder having a ring-shaped crack located at the symmetry plane is subjected to distributed compressive load on its surfaces. The Hankel and Fourier transform techniques are used for the solution of the field equations. By applying the boundary conditions, the singular integral equation in terms of crack surface displacement derivative is derived. By using an appropriate quadrature formula, the integral equation is reduced to a system of linear algebraic equations. Numerical results are obtained for the stress intensity factors at the edges of the crack, surfaces of which are subjected to uniform, linear and parabolic load distributions. (C) 2007 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study is concerned with the fracture of an infinite thick-walled cylinder. The inner surface of the cylinder is stress free and the outer is rigidly fixed. The cylinder having a ring-shaped crack located at the symmetry plane is subjected to distributed compressive load on its surfaces. The Hankel and Fourier transform techniques are used for the solution of the field equations. By applying the boundary conditions, the singular integral equation in terms of crack surface displacement derivative is derived. By using an appropriate quadrature formula, the integral equation is reduced to a system of linear algebraic equations. Numerical results are obtained for the stress intensity factors at the edges of the crack, surfaces of which are subjected to uniform, linear and parabolic load distributions. (C) 2007 Elsevier Ltd. All rights reserved. |
Prof. Dr. Erdal Çetkin
Educational Background
B.Sc. Kocaeli University, Turkey, Mechanical Engineering, 2007
M.Sc. Duke University, USA, Mechanical Engineering and Materials Science, 2010
Ph.D. Duke University, USA, Mechanical Engineering and Materials Science, 2013
Research Interests
- Vascular structures
- Self-cooling
- Self-healing
- Constructal theory
- Heat transfer enhancement
- Electronic cooling
- +90 232 750 6713
- +90 232 750 6701
- Mechanical Engineering Building (119)
Publications
2025 |
Yilmaz, Mert; Cetkin, Erdal; Akca, Hakan Investigation of the effects of various parameters on wireless power transfer efficiency Journal Article 193 , 2025. @article{Yilmaz2025, title = {Investigation of the effects of various parameters on wireless power transfer efficiency}, author = {Mert Yilmaz and Erdal Cetkin and Hakan Akca}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85218449790&doi=10.1016%2fj.aeue.2025.155723&partnerID=40&md5=0bc452bac2c898223de93a8526beba8b}, doi = {10.1016/j.aeue.2025.155723}, year = {2025}, date = {2025-01-01}, volume = {193}, abstract = {Electric vehicles have dominated the automotive market, especially in recent years. However, the charging problem that stresses drivers continues. Although conductive charging is an established technology, it still needs to meet user expectations fully. On the other hand, wireless charging technology attracts users’ attention with dynamic charging features. Although this technology improves daily, efficiency is not at the desired level. In this study, a wireless power transfer system was designed for electric vehicles, and the factors affecting the charging efficiency were investigated. This system consists of an inverter, a compensation system, and a load. The efficiency of the system according to cable type, air gap, cooling, and pulse-width modulation parameters was observed through 40 experiments, each lasting 20 min. In addition to efficiency, the frequency behavior was also investigated. Experimental results were compared with models designed in MATLAB and ANSYS software. The average errors between the experimental and simulation results are 1.75, 2.03, 1.85, 1.58, and 2.00% for air gaps of 19–20, 55–56, 91–92, 127–128, and 145–146 mm, respectively. Power was transferred wirelessly with a minimum efficiency of 59.25% at a 145 mm air gap and a maximum efficiency of 85.74% at a 56 mm air gap in 300 W tests. © 2025 Elsevier GmbH}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electric vehicles have dominated the automotive market, especially in recent years. However, the charging problem that stresses drivers continues. Although conductive charging is an established technology, it still needs to meet user expectations fully. On the other hand, wireless charging technology attracts users’ attention with dynamic charging features. Although this technology improves daily, efficiency is not at the desired level. In this study, a wireless power transfer system was designed for electric vehicles, and the factors affecting the charging efficiency were investigated. This system consists of an inverter, a compensation system, and a load. The efficiency of the system according to cable type, air gap, cooling, and pulse-width modulation parameters was observed through 40 experiments, each lasting 20 min. In addition to efficiency, the frequency behavior was also investigated. Experimental results were compared with models designed in MATLAB and ANSYS software. The average errors between the experimental and simulation results are 1.75, 2.03, 1.85, 1.58, and 2.00% for air gaps of 19–20, 55–56, 91–92, 127–128, and 145–146 mm, respectively. Power was transferred wirelessly with a minimum efficiency of 59.25% at a 145 mm air gap and a maximum efficiency of 85.74% at a 56 mm air gap in 300 W tests. © 2025 Elsevier GmbH |
Aydın, Sevgi; Samancıoğlu, Umut Ege; Savcı, İsmail Hakkı; Yiğit, Kadri Süleyman; Çetkin, Erdal Impact of Cooling Strategies and Cell Housing Materials on Lithium-Ion Battery Thermal Management Performance Journal Article 18 (6), 2025. @article{Aydın2025, title = {Impact of Cooling Strategies and Cell Housing Materials on Lithium-Ion Battery Thermal Management Performance}, author = {Sevgi Aydın and Umut Ege Samancıoğlu and İsmail Hakkı Savcı and Kadri Süleyman Yiğit and Erdal Çetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-105001137038&doi=10.3390%2fen18061379&partnerID=40&md5=96e267c1fe7da5f9c62ba926f86f7063}, doi = {10.3390/en18061379}, year = {2025}, date = {2025-01-01}, volume = {18}, number = {6}, abstract = {The transition to renewable energy sources from fossil fuels requires that the harvested energy be stored because of the intermittent nature of renewable sources. Thus, lithium-ion batteries have become a widely utilized power source in both daily life and industrial applications due to their high power output and long lifetime. In order to ensure the safe operation of these batteries at their desired power and capacities, it is crucial to implement a thermal management system (TMS) that effectively controls battery temperature. In this study, the thermal performance of a 1S14P lithium-ion battery module composed of cylindrical 18650 cells was compared for distinct cases of natural convection (no cooling), forced air convection, and phase change material (PCM) cooling. During the tests, the greatest temperatures were reached at a 2C discharge rate; the maximum module temperature reached was 55.4 °C under the natural convection condition, whereas forced air convection and PCM cooling reduced the maximum module temperature to 46.1 °C and 52.3 °C, respectively. In addition, contacting the battery module with an aluminum mass without using an active cooling element reduced the temperature to 53.4 °C. The polyamide battery housing (holder) used in the module limited the cooling performance. Thus, simulations on alternative materials document how the cooling efficiency can be increased. © 2025 by the authors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The transition to renewable energy sources from fossil fuels requires that the harvested energy be stored because of the intermittent nature of renewable sources. Thus, lithium-ion batteries have become a widely utilized power source in both daily life and industrial applications due to their high power output and long lifetime. In order to ensure the safe operation of these batteries at their desired power and capacities, it is crucial to implement a thermal management system (TMS) that effectively controls battery temperature. In this study, the thermal performance of a 1S14P lithium-ion battery module composed of cylindrical 18650 cells was compared for distinct cases of natural convection (no cooling), forced air convection, and phase change material (PCM) cooling. During the tests, the greatest temperatures were reached at a 2C discharge rate; the maximum module temperature reached was 55.4 °C under the natural convection condition, whereas forced air convection and PCM cooling reduced the maximum module temperature to 46.1 °C and 52.3 °C, respectively. In addition, contacting the battery module with an aluminum mass without using an active cooling element reduced the temperature to 53.4 °C. The polyamide battery housing (holder) used in the module limited the cooling performance. Thus, simulations on alternative materials document how the cooling efficiency can be increased. © 2025 by the authors. |
Yarimca, Gulsah; Jensen, Anders Christian Solberg; Cetkin, Erdal High Accuracy and Applicability Battery Aging Models for Electric Vehicle Applications Journal Article 172 (1), 2025. @article{Yarimca2025, title = {High Accuracy and Applicability Battery Aging Models for Electric Vehicle Applications}, author = {Gulsah Yarimca and Anders Christian Solberg Jensen and Erdal Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85215255368&doi=10.1149%2f1945-7111%2fada73e&partnerID=40&md5=8ee8a170237b3fac74979ff543dc26a5}, doi = {10.1149/1945-7111/ada73e}, year = {2025}, date = {2025-01-01}, volume = {172}, number = {1}, abstract = {Batteries have gained significant attention due to their numerous advantages in applications such as electric vehicles. One of the factors limiting industry adoption is the aging of batteries. The characteristics of battery aging vary depending on many factors such as battery type, electrochemical reactions and operating conditions. Here we document the comparison of semi-empirical aging models (SEM), highlighting limitations and challenges. In addition, four SEMs are proposed. The usability and compatibility of these models are evaluated using experimental data from various sources including the Horizon 2020 Helios Project. The optimized parameters of each model are documented via linear regression and genetic algorithms. The results show that the genetic algorithm approach provides higher accuracy in comparison to the linear regression. The documented SEMs reveal better prediction performance than the literature of calendar obsolescence with SEM-3 and 7 performing particularly well in predicting capacity loss for the Helios dataset with low errors, i.e. 0.43 and 0.79 RMSE, respectively. The range of RMSE values for model predictions across all the datasets ranges from 0.196 to 3.903. This study aims to document the accuracy of SEMs both from the literature and proposed in the paper relative to battery ageing data from distinct sources. © 2025 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Batteries have gained significant attention due to their numerous advantages in applications such as electric vehicles. One of the factors limiting industry adoption is the aging of batteries. The characteristics of battery aging vary depending on many factors such as battery type, electrochemical reactions and operating conditions. Here we document the comparison of semi-empirical aging models (SEM), highlighting limitations and challenges. In addition, four SEMs are proposed. The usability and compatibility of these models are evaluated using experimental data from various sources including the Horizon 2020 Helios Project. The optimized parameters of each model are documented via linear regression and genetic algorithms. The results show that the genetic algorithm approach provides higher accuracy in comparison to the linear regression. The documented SEMs reveal better prediction performance than the literature of calendar obsolescence with SEM-3 and 7 performing particularly well in predicting capacity loss for the Helios dataset with low errors, i.e. 0.43 and 0.79 RMSE, respectively. The range of RMSE values for model predictions across all the datasets ranges from 0.196 to 3.903. This study aims to document the accuracy of SEMs both from the literature and proposed in the paper relative to battery ageing data from distinct sources. © 2025 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. |
2024 |
Samancıoğlu, Umut Ege; Göçmen, Sinan; Madani, Seyed Saeed; Ziebert, Carlos; Nuno, Fernando; Huang, Jack; Gao, Frank; Çetkin, Erdal An experimental and comparative study on passive and active PCM cooling of a battery with/out copper mesh and investigation of PCM mixtures Journal Article 103 , 2024. @article{Samancıoğlu2024, title = {An experimental and comparative study on passive and active PCM cooling of a battery with/out copper mesh and investigation of PCM mixtures}, author = {Umut Ege Samancıoğlu and Sinan Göçmen and Seyed Saeed Madani and Carlos Ziebert and Fernando Nuno and Jack Huang and Frank Gao and Erdal Çetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85206987623&doi=10.1016%2fj.est.2024.114262&partnerID=40&md5=fdab2cfeba033f208b908b87d53c2bc1}, doi = {10.1016/j.est.2024.114262}, year = {2024}, date = {2024-01-01}, volume = {103}, abstract = {The carbon emission contribution to global warming accelerated both research on and transition to electric vehicles (EVs). Drivers demand high power, fast acceleration and less charging times. All these demands require high C rate charging/discharging demands from batteries. The rate of heat generation is exponentially proportional to C rates which decreases battery lifetime and may lead to thermal runaway. However, a battery thermal management system decreases thermal runaway risk and decelerates battery degradation via controlling battery temperature. In this paper, we first document the thermal conductivity enhancement via copper foam into phase change material (PCM) domain to uncover their possible use in EV thermal management applications. Maximum 15.93 times increment is achieved with a specific copper foam. Then, physical properties and behaviors of distinct PCM mixtures are documented. Homogeneity of mixtures is associated with the chemistry of PCMs and the mixture melting point is proportional to the volume weighted average of melting temperatures. The results document that the PCM with relatively lower melting point is beneficial when end of discharge temperatures considered, except for high discharge rate of 2C. Temperature uniformity across the battery increases with relatively higher melting point PCM. Experiments also document that the amount of PCM volume lost via insertion of copper foam yields higher end of discharge temperatures. Overall, both PCM and copper foam enhances temperature homogeneity and their benefit becomes more sensible during drive cycles relative to continuous charge/discharge use cases. © 2024 The Authors}, keywords = {}, pubstate = {published}, tppubtype = {article} } The carbon emission contribution to global warming accelerated both research on and transition to electric vehicles (EVs). Drivers demand high power, fast acceleration and less charging times. All these demands require high C rate charging/discharging demands from batteries. The rate of heat generation is exponentially proportional to C rates which decreases battery lifetime and may lead to thermal runaway. However, a battery thermal management system decreases thermal runaway risk and decelerates battery degradation via controlling battery temperature. In this paper, we first document the thermal conductivity enhancement via copper foam into phase change material (PCM) domain to uncover their possible use in EV thermal management applications. Maximum 15.93 times increment is achieved with a specific copper foam. Then, physical properties and behaviors of distinct PCM mixtures are documented. Homogeneity of mixtures is associated with the chemistry of PCMs and the mixture melting point is proportional to the volume weighted average of melting temperatures. The results document that the PCM with relatively lower melting point is beneficial when end of discharge temperatures considered, except for high discharge rate of 2C. Temperature uniformity across the battery increases with relatively higher melting point PCM. Experiments also document that the amount of PCM volume lost via insertion of copper foam yields higher end of discharge temperatures. Overall, both PCM and copper foam enhances temperature homogeneity and their benefit becomes more sensible during drive cycles relative to continuous charge/discharge use cases. © 2024 The Authors |
Yarimca, Gulsah; Cetkin, Erdal Review of Cell Level Battery (Calendar and Cycling) Aging Models: Electric Vehicles Journal Article 10 (11), 2024. @article{Yarimca2024, title = {Review of Cell Level Battery (Calendar and Cycling) Aging Models: Electric Vehicles}, author = {Gulsah Yarimca and Erdal Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85210308179&doi=10.3390%2fbatteries10110374&partnerID=40&md5=daec7f515aa3fc5e0d21af641a8592ac}, doi = {10.3390/batteries10110374}, year = {2024}, date = {2024-01-01}, volume = {10}, number = {11}, abstract = {Electrochemical battery cells have been a focus of attention due to their numerous advantages in distinct applications recently, such as electric vehicles. A limiting factor for adaptation by the industry is related to the aging of batteries over time. Characteristics of battery aging vary depending on many factors such as battery type, electrochemical reactions, and operation conditions. Aging could be considered in two sections according to its type: calendar and cycling. We examine the stress factors affecting these two types of aging in detail under subheadings and review the battery aging literature with a comprehensive approach. This article presents a review of empirical and semi-empirical modeling techniques and aging studies, focusing on the trends observed between different studies and highlighting the limitations and challenges of the various models. © 2024 by the authors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemical battery cells have been a focus of attention due to their numerous advantages in distinct applications recently, such as electric vehicles. A limiting factor for adaptation by the industry is related to the aging of batteries over time. Characteristics of battery aging vary depending on many factors such as battery type, electrochemical reactions, and operation conditions. Aging could be considered in two sections according to its type: calendar and cycling. We examine the stress factors affecting these two types of aging in detail under subheadings and review the battery aging literature with a comprehensive approach. This article presents a review of empirical and semi-empirical modeling techniques and aging studies, focusing on the trends observed between different studies and highlighting the limitations and challenges of the various models. © 2024 by the authors. |
Samancoğlu, Umut Ege; Koşar, Ali; Cetkin, Erdal Optimization of Y-Shaped Micro-Mixers With a Mixing Chamber for Increased Mixing Efficiency and Decreased Pressure Drop Journal Article 146 (4), 2024. @article{Samancoğlu2024, title = {Optimization of Y-Shaped Micro-Mixers With a Mixing Chamber for Increased Mixing Efficiency and Decreased Pressure Drop}, author = {Umut Ege Samancoğlu and Ali Koşar and Erdal Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85185843804&doi=10.1115%2f1.4064443&partnerID=40&md5=329f6f13e703302e62731d685c727b4e}, doi = {10.1115/1.4064443}, year = {2024}, date = {2024-01-01}, volume = {146}, number = {4}, abstract = {In this study, Y-shaped micromixers with mixing chamber design optimized as rotation and chaotic advection in the fluid domain increase with the chamber. Motivated by the advantages of Y-shaped mixers, a parametric study was performed for inlet angles (a, b), inlet channel eccentricities (x-ecc, z-ecc) and length scale ratios (L1/L2, D1/D2, and Vsp). z-eccentricity is introduced in addition to x-eccentricity to create a design that further enhances the swirl and chaotic advection inside mixing chamber for the first time. The results reveal that the maximum mixing efficiency can be achieved for Reynolds number of 81 and a, b, x-ecc, z-ecc, D1/D2, and L1/L2 values of 210◦, 60◦, 20 lm, 20 lm, 1.8, and 4, respectively. In addition, the proposed Y-shaped micromixer leads to a lower pressure drop (at least 50% reduction for all Reynolds numbers) in comparison to competing design. The maximum reduction in pressure drop is 72% less than the curved-straight-curved (CSC) (Re ¼ 81) with mixing efficiency of 88% and pressure drop of 9244.4 Pa. Overall, an outstanding mixing efficiency was offered over a wide range of Reynolds numbers with distinctly low pressure drop and a compact micromixer design, which could be beneficial for a wide variety of applications where volume and pumping power are limited. Copyright © 2024 by ASME.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, Y-shaped micromixers with mixing chamber design optimized as rotation and chaotic advection in the fluid domain increase with the chamber. Motivated by the advantages of Y-shaped mixers, a parametric study was performed for inlet angles (a, b), inlet channel eccentricities (x-ecc, z-ecc) and length scale ratios (L1/L2, D1/D2, and Vsp). z-eccentricity is introduced in addition to x-eccentricity to create a design that further enhances the swirl and chaotic advection inside mixing chamber for the first time. The results reveal that the maximum mixing efficiency can be achieved for Reynolds number of 81 and a, b, x-ecc, z-ecc, D1/D2, and L1/L2 values of 210◦, 60◦, 20 lm, 20 lm, 1.8, and 4, respectively. In addition, the proposed Y-shaped micromixer leads to a lower pressure drop (at least 50% reduction for all Reynolds numbers) in comparison to competing design. The maximum reduction in pressure drop is 72% less than the curved-straight-curved (CSC) (Re ¼ 81) with mixing efficiency of 88% and pressure drop of 9244.4 Pa. Overall, an outstanding mixing efficiency was offered over a wide range of Reynolds numbers with distinctly low pressure drop and a compact micromixer design, which could be beneficial for a wide variety of applications where volume and pumping power are limited. Copyright © 2024 by ASME. |
2023 |
Gocmen, Sinan; Cetkin, Erdal Experimental Investigation of Air Cooling With/Out Tab Cooling in Cell and Module Levels for Thermal Uniformity in Battery Packs Journal Article Journal of Heat Transfer, 145 (2), 2023. @article{Gocmen2023, title = {Experimental Investigation of Air Cooling With/Out Tab Cooling in Cell and Module Levels for Thermal Uniformity in Battery Packs}, author = {Sinan Gocmen and Erdal Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85143991374&doi=10.1115%2f1.4055939&partnerID=40&md5=efb2c14fb28632d261da28c8f71ad9c5}, doi = {10.1115/1.4055939}, year = {2023}, date = {2023-01-01}, journal = {Journal of Heat Transfer}, volume = {145}, number = {2}, abstract = {Catastrophic effects of global warming and environmental pollution are becoming more evident each day, and reduction in fossil fuel consumption is an urgent need. Thus, electric vehicles powered by sustainable energy sources are becoming a major interest. However, there are some challenges such as safety, limited range, long charging times, and battery life which are inhibitory to the adaptation of them. One of the biggest reasons for these challenges is the relationship between battery degradation and temperature which can be eliminated if batteries can be kept at the optimum temperature range. Here, the effects of three distinct (natural convection, forced convection, and tab cooling) methodology were experimentally compared at both the cell and module levels (six serial 7.5 Ah Kokam pouch cells, 1P6S) for thermal management of lithium-ion cells. The experiments were conducted at a discharge rate of 3C with ambient temperatures of 24 ◦C and 29 ◦C. The cell-level test results show that the tab cooling yields 32.5% better thermal uniformity in comparison to the other techniques. Furthermore, tab cooling yields better temperature uniformity with and without air convection as the hot spots occurring near the tabs is eliminated. For the module level, the forced air convection method stands out as the best option with a 4.3% temperature deviation between cells and maximum cell temperature of 39 ◦C. Overall, the results show that a hybrid approach with tab cooling would be beneficial in terms of temperature homogeneity especially in high capacity electric vehicle battery cells. Copyright © 2023 by ASME.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Catastrophic effects of global warming and environmental pollution are becoming more evident each day, and reduction in fossil fuel consumption is an urgent need. Thus, electric vehicles powered by sustainable energy sources are becoming a major interest. However, there are some challenges such as safety, limited range, long charging times, and battery life which are inhibitory to the adaptation of them. One of the biggest reasons for these challenges is the relationship between battery degradation and temperature which can be eliminated if batteries can be kept at the optimum temperature range. Here, the effects of three distinct (natural convection, forced convection, and tab cooling) methodology were experimentally compared at both the cell and module levels (six serial 7.5 Ah Kokam pouch cells, 1P6S) for thermal management of lithium-ion cells. The experiments were conducted at a discharge rate of 3C with ambient temperatures of 24 ◦C and 29 ◦C. The cell-level test results show that the tab cooling yields 32.5% better thermal uniformity in comparison to the other techniques. Furthermore, tab cooling yields better temperature uniformity with and without air convection as the hot spots occurring near the tabs is eliminated. For the module level, the forced air convection method stands out as the best option with a 4.3% temperature deviation between cells and maximum cell temperature of 39 ◦C. Overall, the results show that a hybrid approach with tab cooling would be beneficial in terms of temperature homogeneity especially in high capacity electric vehicle battery cells. Copyright © 2023 by ASME. |
Gungor, Sahin; Gocmen, Sinan; Cetkin, Erdal A review on battery thermal management strategies in lithium-ion and post-lithium batteries for electric vehicles Journal Article Journal of Thermal Engineering, 9 (4), pp. 1078 – 1099, 2023, (All Open Access, Gold Open Access, Green Open Access). @article{Gungor20231078, title = {A review on battery thermal management strategies in lithium-ion and post-lithium batteries for electric vehicles}, author = {Sahin Gungor and Sinan Gocmen and Erdal Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85169015170&doi=10.18186%2fthermal.1334238&partnerID=40&md5=263294fb861dd4fbc4a7751e2bb7079d}, doi = {10.18186/thermal.1334238}, year = {2023}, date = {2023-01-01}, journal = {Journal of Thermal Engineering}, volume = {9}, number = {4}, pages = {1078 – 1099}, abstract = {Electrification on transportation and electricity generation via renewable sources play a vital role to diminish the effects of energy usage on the environment. Transition from the conventional fuels to renewables for transportation and electricity generation demands the storage of electricity in great capacities with desired power densities and relatively high C-rate values. Yet, thermal and electrical characteristics vary greatly depending on the chemistry and structure of battery cells. At this point, lithium-ion (Li-ion) batteries are more suitable in most applications due to their superiorities such as long lifetime, high recyclability, and capacities. However, exothermic electrochemical reactions yield temperature to increase suddenly which affects the degradation in cells, ageing, and electrochemical reaction kinetics. Therefore, strict temperature control increases battery lifetime and eliminates undesired situations such as layer degradation and thermal runaway. In the literature, there are many distinct battery thermal management strategies to effectively control battery cell temperatures. These strategies vary based on the geometrical form, size, capacity, and chemistry of the battery cells. Here, we focus on proposed battery thermal management strategies and current applications in the electric vehicle (EV) industry. In this review, various battery thermal management strategies are documented and compared in detail with respect to geometry, thermal uniformity, coolant type and heat transfer methodology for Li-ion and post-lithium batteries. © Copyright 2021, Yıldız Technical University. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).}, note = {All Open Access, Gold Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrification on transportation and electricity generation via renewable sources play a vital role to diminish the effects of energy usage on the environment. Transition from the conventional fuels to renewables for transportation and electricity generation demands the storage of electricity in great capacities with desired power densities and relatively high C-rate values. Yet, thermal and electrical characteristics vary greatly depending on the chemistry and structure of battery cells. At this point, lithium-ion (Li-ion) batteries are more suitable in most applications due to their superiorities such as long lifetime, high recyclability, and capacities. However, exothermic electrochemical reactions yield temperature to increase suddenly which affects the degradation in cells, ageing, and electrochemical reaction kinetics. Therefore, strict temperature control increases battery lifetime and eliminates undesired situations such as layer degradation and thermal runaway. In the literature, there are many distinct battery thermal management strategies to effectively control battery cell temperatures. These strategies vary based on the geometrical form, size, capacity, and chemistry of the battery cells. Here, we focus on proposed battery thermal management strategies and current applications in the electric vehicle (EV) industry. In this review, various battery thermal management strategies are documented and compared in detail with respect to geometry, thermal uniformity, coolant type and heat transfer methodology for Li-ion and post-lithium batteries. © Copyright 2021, Yıldız Technical University. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). |
Coşkun, Turgay; Çetkin, Erdal Vascularized mini cooling channels to achieve temperature uniformity: Battery thermal management and electronic cooling Journal Article Research on Engineering Structures and Materials, 9 (3), pp. 375 – 385, 2023, (All Open Access, Bronze Open Access). @article{Coşkun2023375, title = {Vascularized mini cooling channels to achieve temperature uniformity: Battery thermal management and electronic cooling}, author = {Turgay Coşkun and Erdal Çetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85172141689&doi=10.17515%2fresm2022.585ma1121&partnerID=40&md5=9ad60c3fb4eeb671fd48e7749faec21d}, doi = {10.17515/resm2022.585ma1121}, year = {2023}, date = {2023-01-01}, journal = {Research on Engineering Structures and Materials}, volume = {9}, number = {3}, pages = {375 – 385}, abstract = {Here we propose to use of distinct vascularized plates to be used in the applications of battery thermal management and electronic cooling. The temperatures of battery cells increase during charge and discharge; and elevated temperature values in them accelerated degradation and even may trigger battery fire because of the thermal runaway. Therefore, thermal management system is a necessity for battery packs to increase the battery performance and diminish the risk factors in the electric vehicles. Generally, high amount of heat is released in the high capacity (>15 Ah) cells in short time interval under fast charge/discharge conditions; thus, thermal management of the battery system can be achieved with liquid cooling in that situation. A silicon heater system which represents the thermal behavior of a battery cell is manufactured based on the literature and it is used in experiments. Such a method has not proposed up to now in the literature, so the study may be creating a new experimental procedure for future studies without the risk of battery fire/degradation to uncover even extreme conditions experimentally. Electronic cooling is also in prime importance due to enhanced computing requirement of current systems, and vascularized plates can solve the hot spot problems occurring with decreased energy consumption. According to the results, the cooling capacity of the vascularized plates are calculated as 20W, and a battery cell can be kept within its optimal operating temperature range when the heat loads up to 30W. Also, the temperature uniformity along the surface of mimic of the battery is satisfied by vascularized plates. © 2023 MIM Research Group. All rights reserved.}, note = {All Open Access, Bronze Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here we propose to use of distinct vascularized plates to be used in the applications of battery thermal management and electronic cooling. The temperatures of battery cells increase during charge and discharge; and elevated temperature values in them accelerated degradation and even may trigger battery fire because of the thermal runaway. Therefore, thermal management system is a necessity for battery packs to increase the battery performance and diminish the risk factors in the electric vehicles. Generally, high amount of heat is released in the high capacity (>15 Ah) cells in short time interval under fast charge/discharge conditions; thus, thermal management of the battery system can be achieved with liquid cooling in that situation. A silicon heater system which represents the thermal behavior of a battery cell is manufactured based on the literature and it is used in experiments. Such a method has not proposed up to now in the literature, so the study may be creating a new experimental procedure for future studies without the risk of battery fire/degradation to uncover even extreme conditions experimentally. Electronic cooling is also in prime importance due to enhanced computing requirement of current systems, and vascularized plates can solve the hot spot problems occurring with decreased energy consumption. According to the results, the cooling capacity of the vascularized plates are calculated as 20W, and a battery cell can be kept within its optimal operating temperature range when the heat loads up to 30W. Also, the temperature uniformity along the surface of mimic of the battery is satisfied by vascularized plates. © 2023 MIM Research Group. All rights reserved. |
Coşkun, Turgay; Çetkin, Erdal Cold plate enabling air and liquid cooling simultaneously: Experimental study for battery pack thermal management and electronic cooling Journal Article International Journal of Heat and Mass Transfer, 217 , 2023. @article{Coşkun2023b, title = {Cold plate enabling air and liquid cooling simultaneously: Experimental study for battery pack thermal management and electronic cooling}, author = {Turgay Coşkun and Erdal Çetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171470128&doi=10.1016%2fj.ijheatmasstransfer.2023.124702&partnerID=40&md5=1857b720cbfc7b433f17d682d0c99b3a}, doi = {10.1016/j.ijheatmasstransfer.2023.124702}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Heat and Mass Transfer}, volume = {217}, abstract = {The temperature of cells varies greatly during dis/charge while their performance and lifetime are greatly affected by this fluctuation. Elevated temperatures may yield battery fire due to thermal runaway as well they accelerate ageing and capacity fade of cells. Thermal management systems are a necessity for electric vehicles to extend the lifetime of battery cells and eliminate any fire risks, especially for fast dis/charging applications. Here, we document a hybrid cold plate with a working fluid(s) of sole air or liquid as well as both of them. Hybridization of air and liquid cooling promises to minimize energy consumption requirements during a charge/discharge cycle by combining the benefits of both thermal management strategies if energy management is controlled accordingly. The temperature of each cell can be kept below 30°C with the proposed hybrid cooling heat exchanger, and the temperature difference between the cells is reduced by 30 % relative to liquid cooling. The maximum temperatures are decreased by 18 % and 3 % in hybrid cooling when compared to air and water cooling, respectively. Furthermore, a step function combining various discharge rates (1C and 3C) was employed in experiments to mimic a realistic situation, i.e. variable C-rate rather than constant. The results show that the temperature of the battery cells can be kept below 30°C with air cooling for variable discharge rate and the effect of contact resistance should not be overlooked for liquid cooling. Furthermore, the possible use of the proposed hybrid cold plates is surveyed in the cooling of electronic devices which produce more and continuous heat than cells. Therefore, three resistance heaters with a capacity of 50W are used in experiments as well. The results show that the proposed cold plates could be used in both electronics cooling and battery thermal management with a control algorithm to switch between sole working fluid and combination modes which could be developed based on the results of this paper. © 2023}, keywords = {}, pubstate = {published}, tppubtype = {article} } The temperature of cells varies greatly during dis/charge while their performance and lifetime are greatly affected by this fluctuation. Elevated temperatures may yield battery fire due to thermal runaway as well they accelerate ageing and capacity fade of cells. Thermal management systems are a necessity for electric vehicles to extend the lifetime of battery cells and eliminate any fire risks, especially for fast dis/charging applications. Here, we document a hybrid cold plate with a working fluid(s) of sole air or liquid as well as both of them. Hybridization of air and liquid cooling promises to minimize energy consumption requirements during a charge/discharge cycle by combining the benefits of both thermal management strategies if energy management is controlled accordingly. The temperature of each cell can be kept below 30°C with the proposed hybrid cooling heat exchanger, and the temperature difference between the cells is reduced by 30 % relative to liquid cooling. The maximum temperatures are decreased by 18 % and 3 % in hybrid cooling when compared to air and water cooling, respectively. Furthermore, a step function combining various discharge rates (1C and 3C) was employed in experiments to mimic a realistic situation, i.e. variable C-rate rather than constant. The results show that the temperature of the battery cells can be kept below 30°C with air cooling for variable discharge rate and the effect of contact resistance should not be overlooked for liquid cooling. Furthermore, the possible use of the proposed hybrid cold plates is surveyed in the cooling of electronic devices which produce more and continuous heat than cells. Therefore, three resistance heaters with a capacity of 50W are used in experiments as well. The results show that the proposed cold plates could be used in both electronics cooling and battery thermal management with a control algorithm to switch between sole working fluid and combination modes which could be developed based on the results of this paper. © 2023 |
2022 |
Gungor, Sahin; Cetkin, Erdal; Lorente, Sylvie Canopy-to-canopy liquid cooling for the thermal management of lithium-ion batteries, a constructal approach Journal Article INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 182 , 2022. @article{WOS:000709733600003, title = {Canopy-to-canopy liquid cooling for the thermal management of lithium-ion batteries, a constructal approach}, author = {Sahin Gungor and Erdal Cetkin and Sylvie Lorente}, doi = {10.1016/j.ijheatmasstransfer.2021.121918}, year = {2022}, date = {2022-01-01}, journal = {INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, volume = {182}, abstract = {With the growing interest on electric vehicles comes the question of the thermal management of their battery pack. In this work, we propose a thermally efficient solution consisting in inserting between the cells a liquid cooling system based on constructal canopy-to-canopy architectures. In such systems, the cooling fluid is driven from a trunk channel to perpendicular branches that make the tree canopy. An opposite tree collects the liquid in such a way that the two trees match canopy-to-canopy. The configuration of the cooling solution is predicted following the constructal methodology, leading to the choice of the hydraulic diameter ratios. We show that such configurations allow extracting most of the non-uniformly generated heat by the battery cell during the discharging phase, while using a small mass flow rate. (c) 2021 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } With the growing interest on electric vehicles comes the question of the thermal management of their battery pack. In this work, we propose a thermally efficient solution consisting in inserting between the cells a liquid cooling system based on constructal canopy-to-canopy architectures. In such systems, the cooling fluid is driven from a trunk channel to perpendicular branches that make the tree canopy. An opposite tree collects the liquid in such a way that the two trees match canopy-to-canopy. The configuration of the cooling solution is predicted following the constructal methodology, leading to the choice of the hydraulic diameter ratios. We show that such configurations allow extracting most of the non-uniformly generated heat by the battery cell during the discharging phase, while using a small mass flow rate. (c) 2021 Elsevier Ltd. All rights reserved. |
2021 |
Demirkiran, Ismail Gurkan; Cetkin, Erdal Emergence of rectangular shell shape in thermal energy storage applications: Fitting melted phase changing material in a fixed space Journal Article JOURNAL OF ENERGY STORAGE, 37 , 2021. @article{WOS:000641410200002, title = {Emergence of rectangular shell shape in thermal energy storage applications: Fitting melted phase changing material in a fixed space}, author = {Ismail Gurkan Demirkiran and Erdal Cetkin}, doi = {10.1016/j.est.2021.102455}, year = {2021}, date = {2021-05-01}, journal = {JOURNAL OF ENERGY STORAGE}, volume = {37}, abstract = {Here we document the effect of heat transfer fluid (HTF) tube position and shell shape on the melting time and sensible energy requirement for melting a phase change material (PCM) in a multitube latent heat thermal energy storage (LHTES) application. Tube location and shell shape are essential as the shape of the melted region, i.e. similar to the boundary layer, affects convective heat transfer performance. HTF tube total area is fixed in all cases to have the same amount of PCM. In order to eliminate the effect of heat transfer surface area variation, results of two- and four-tube configurations were compared within themselves. Liquid fraction, sensible enthalpy content, and latent/sensible enthalpy ratio relative to time were documented for two and four HTF configurations in various shell shape and tube locations. Results show that eccentric two tubes with rectangular shell decreases melting time and sensible energy requirement from 67 min to 32 min and from 161.8 kJ/kg to 136.3 kJ/kg for 72.3% liquid fraction, respectively, in comparison to the concentric tubes with the circular shell. When the number of HTF tubes increases to four, then the required melting time and sensible energy decrease 80% and 3.8%, respectively, for PCM to melt completely as the concentric tubes and circular shell is replaced with eccentric tubes and rectangular shell. Results of liquid fraction variation relative to time show that S-curve of melting becomes steeper if PCM distribution is such that the intersection of melted regions is delayed. Therefore, melted PCM regions could be packed into a shell that minimizes melting time and required sensible energy. Even rectangular shell shape increases the heat transfer surface (increased heat loss rate) because melting time has decreased greatly, total energy lost to the ambient from the surfaces of shell decreases. Eccentricity slows down the solidification process but due to increased heat loss rate from the surface, rectangular shell enables faster solidification than circular shell shape. There is a trade off in between solidification time and heat loss energy for rectangular channels which can be optimized by selecting proper insulation thickness. Overall, the results show that without any thermal conductivity enhancement (TCE) method, melting performance and latent heat storage capability can be significantly enhanced as decreasing the sensible heat storage by fitting the melted PCM regions into a fixed space for the applications where charging speed is lot faster than discharging.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here we document the effect of heat transfer fluid (HTF) tube position and shell shape on the melting time and sensible energy requirement for melting a phase change material (PCM) in a multitube latent heat thermal energy storage (LHTES) application. Tube location and shell shape are essential as the shape of the melted region, i.e. similar to the boundary layer, affects convective heat transfer performance. HTF tube total area is fixed in all cases to have the same amount of PCM. In order to eliminate the effect of heat transfer surface area variation, results of two- and four-tube configurations were compared within themselves. Liquid fraction, sensible enthalpy content, and latent/sensible enthalpy ratio relative to time were documented for two and four HTF configurations in various shell shape and tube locations. Results show that eccentric two tubes with rectangular shell decreases melting time and sensible energy requirement from 67 min to 32 min and from 161.8 kJ/kg to 136.3 kJ/kg for 72.3% liquid fraction, respectively, in comparison to the concentric tubes with the circular shell. When the number of HTF tubes increases to four, then the required melting time and sensible energy decrease 80% and 3.8%, respectively, for PCM to melt completely as the concentric tubes and circular shell is replaced with eccentric tubes and rectangular shell. Results of liquid fraction variation relative to time show that S-curve of melting becomes steeper if PCM distribution is such that the intersection of melted regions is delayed. Therefore, melted PCM regions could be packed into a shell that minimizes melting time and required sensible energy. Even rectangular shell shape increases the heat transfer surface (increased heat loss rate) because melting time has decreased greatly, total energy lost to the ambient from the surfaces of shell decreases. Eccentricity slows down the solidification process but due to increased heat loss rate from the surface, rectangular shell enables faster solidification than circular shell shape. There is a trade off in between solidification time and heat loss energy for rectangular channels which can be optimized by selecting proper insulation thickness. Overall, the results show that without any thermal conductivity enhancement (TCE) method, melting performance and latent heat storage capability can be significantly enhanced as decreasing the sensible heat storage by fitting the melted PCM regions into a fixed space for the applications where charging speed is lot faster than discharging. |
2020 |
Coskun, Turgay; Cetkin, Erdal A review of heat and fluid flow characteristics in microchannel heat sinks Journal Article HEAT TRANSFER, 49 (8), pp. 4109-4133, 2020, ISSN: 2688-4534. @article{ISI:000595699600002, title = {A review of heat and fluid flow characteristics in microchannel heat sinks}, author = {Turgay Coskun and Erdal Cetkin}, doi = {10.1002/htj.21819}, issn = {2688-4534}, year = {2020}, date = {2020-12-01}, journal = {HEAT TRANSFER}, volume = {49}, number = {8}, pages = {4109-4133}, abstract = {Heat transfer and flow characteristic in microchannel heat sinks (MCHS) are extensively studied in the literature due to high heat transfer rate capability by increased heat transfer surface area relative to the macroscale heat sinks. However, heat transfer and fluid flow characteristics in MCHS differ from conventional ones because of the scaling effects. This review summarizes the studies that are mainly based on heat transfer and fluid flow characteristic in MCHS. There is no consistency among the published results; however, everyone agrees on that there is no new physical phenomenon in microscale that does not exist at macroscale. Only difference between them is that the effect of some physical phenomena such as viscous dissipation, axial heat conduction, entrance effect, rarefaction, and so forth, is negligibly small at macroscale, whereas it is not at microscale. The effect of these physical phenomena on the heat transfer and flow characteristics becomes significant with respect to specified conditions such as Reynolds number, Peclet number, hydraulic diameter, and heat transfer boundary conditions. Here, the literature was reviewed to document when these physical phenomena become significant and insignificant.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Heat transfer and flow characteristic in microchannel heat sinks (MCHS) are extensively studied in the literature due to high heat transfer rate capability by increased heat transfer surface area relative to the macroscale heat sinks. However, heat transfer and fluid flow characteristics in MCHS differ from conventional ones because of the scaling effects. This review summarizes the studies that are mainly based on heat transfer and fluid flow characteristic in MCHS. There is no consistency among the published results; however, everyone agrees on that there is no new physical phenomenon in microscale that does not exist at macroscale. Only difference between them is that the effect of some physical phenomena such as viscous dissipation, axial heat conduction, entrance effect, rarefaction, and so forth, is negligibly small at macroscale, whereas it is not at microscale. The effect of these physical phenomena on the heat transfer and flow characteristics becomes significant with respect to specified conditions such as Reynolds number, Peclet number, hydraulic diameter, and heat transfer boundary conditions. Here, the literature was reviewed to document when these physical phenomena become significant and insignificant. |
Gocmen, Sinan; Gungor, Sahin; Cetkin, Erdal Thermal management of electric vehicle battery cells with homogeneous coolant and temperature distribution Journal Article JOURNAL OF APPLIED PHYSICS, 127 (23), 2020, ISSN: 0021-8979. @article{ISI:000542961200001, title = {Thermal management of electric vehicle battery cells with homogeneous coolant and temperature distribution}, author = {Sinan Gocmen and Sahin Gungor and Erdal Cetkin}, doi = {10.1063/5.0004453}, issn = {0021-8979}, year = {2020}, date = {2020-06-01}, journal = {JOURNAL OF APPLIED PHYSICS}, volume = {127}, number = {23}, abstract = {Electric vehicles play an integral role in eliminating pollution related to transportation, especially if the electricity is generated via renewable sources. However, storing electricity onboard requires many battery cells. If the temperature of the cells is not strictly regulated, their capacity decreases in time, and they may burn or explode due to thermal runaway. Battery thermal management systems emerged for safe operations by keeping the battery cell temperatures under limit values. However, the current solutions do not yield uniform temperature distribution for all the cells in a pack. Here, we document that constant temperature distribution can be achieved with uniform coolant distribution to the channels located between batteries. The design process of the developed battery pack begins with a design used in current packs. Later, how the shape of the distributor channel affects flow uniformity is documented. Then, the design complexity was increased to satisfy the flow uniformity condition, which is essential for temperature uniformity. The design was altered based on a constructal design methodology with an iterative exhaustive search approach. The uncovered constructal design yields a uniform coolant distribution with a maximum of 0.81% flow rate deviation along channels. The developed design is palpable and easy to manufacture relative to the tapered manifold designs. The results also document that the peak temperature difference between the cells decreases from a maximum of 12K to 0.4K. Furthermore, homogenous distribution of air is one of the limiting factors of the development of metal-air batteries. This paper also documents how air can be distributed uniformly to metal-air battery cells in a battery pack.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electric vehicles play an integral role in eliminating pollution related to transportation, especially if the electricity is generated via renewable sources. However, storing electricity onboard requires many battery cells. If the temperature of the cells is not strictly regulated, their capacity decreases in time, and they may burn or explode due to thermal runaway. Battery thermal management systems emerged for safe operations by keeping the battery cell temperatures under limit values. However, the current solutions do not yield uniform temperature distribution for all the cells in a pack. Here, we document that constant temperature distribution can be achieved with uniform coolant distribution to the channels located between batteries. The design process of the developed battery pack begins with a design used in current packs. Later, how the shape of the distributor channel affects flow uniformity is documented. Then, the design complexity was increased to satisfy the flow uniformity condition, which is essential for temperature uniformity. The design was altered based on a constructal design methodology with an iterative exhaustive search approach. The uncovered constructal design yields a uniform coolant distribution with a maximum of 0.81% flow rate deviation along channels. The developed design is palpable and easy to manufacture relative to the tapered manifold designs. The results also document that the peak temperature difference between the cells decreases from a maximum of 12K to 0.4K. Furthermore, homogenous distribution of air is one of the limiting factors of the development of metal-air batteries. This paper also documents how air can be distributed uniformly to metal-air battery cells in a battery pack. |
2017 |
Cetin, Eylem; Cetkin, Erdal The effect of cavities and T-shaped assembly of fins on overall thermal resistances Journal Article INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY, 35 (4), pp. 944-952, 2017, ISSN: 0392-8764. @article{ISI:000429132900030, title = {The effect of cavities and T-shaped assembly of fins on overall thermal resistances}, author = {Eylem Cetin and Erdal Cetkin}, doi = {10.18280/ijht.350430}, issn = {0392-8764}, year = {2017}, date = {2017-12-01}, journal = {INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY}, volume = {35}, number = {4}, pages = {944-952}, abstract = {In this study, authors show that maximum excess temperature on a heat generating cylindrical solid domain can be minimized with numerically optimized rectangular cavities and T-shaped fins. The effect of the cavities and the fins on overall thermal resistances were compared while their volume fraction in a unit volume element is fixed. Furthermore, the designs correspond to the minimum thermal resistance were uncovered for two types of flows; parallel and cross-flow. The governing equations of the heat transfer and the fluid flow were solved simultaneously in order to show the effects of design on the flow characteristics and the thermal performance. Two-dimensional solution domain was used to uncover the thermal performance in cross-flow case because the flow direction is perpendicular to the heat transfer surface area of the heat generating domain. However, three-dimensional domain was used in parallel flow case because the fluid flows along the outer surface of the heat generating domain. For the cross-flow case, the results show that T-shaped assembly of fins with longer stem and shorter tributaries correspond to the lower peak temperature. In addition, the results also show that there is an optimal cavity shape that minimizes the peak temperature. This optimal shape becomes thinner when the number of the cavities increase. In parallel flow case, fins with thicker and shorter stem and longer tributaries correspond to the minimum excess temperature. In addition, the longer and thinner cavities increase the thermal performance in parallel flow case.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, authors show that maximum excess temperature on a heat generating cylindrical solid domain can be minimized with numerically optimized rectangular cavities and T-shaped fins. The effect of the cavities and the fins on overall thermal resistances were compared while their volume fraction in a unit volume element is fixed. Furthermore, the designs correspond to the minimum thermal resistance were uncovered for two types of flows; parallel and cross-flow. The governing equations of the heat transfer and the fluid flow were solved simultaneously in order to show the effects of design on the flow characteristics and the thermal performance. Two-dimensional solution domain was used to uncover the thermal performance in cross-flow case because the flow direction is perpendicular to the heat transfer surface area of the heat generating domain. However, three-dimensional domain was used in parallel flow case because the fluid flows along the outer surface of the heat generating domain. For the cross-flow case, the results show that T-shaped assembly of fins with longer stem and shorter tributaries correspond to the lower peak temperature. In addition, the results also show that there is an optimal cavity shape that minimizes the peak temperature. This optimal shape becomes thinner when the number of the cavities increase. In parallel flow case, fins with thicker and shorter stem and longer tributaries correspond to the minimum excess temperature. In addition, the longer and thinner cavities increase the thermal performance in parallel flow case. |
Cetkin, Erdal JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, 139 (8), 2017, ISSN: 0022-1481. @article{ISI:000426124400018, title = {Constructal Microdevice Manifold Design With Uniform Flow Rate Distribution by Consideration of the Tree-Branching Rule of Leonardo da Vinci and Hess-Murray Rule}, author = {Erdal Cetkin}, doi = {10.1115/1.4036089}, issn = {0022-1481}, year = {2017}, date = {2017-08-01}, journal = {JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, volume = {139}, number = {8}, abstract = {In this paper, we show how the design of a microdevice manifold should be tapered for uniform flow rate distribution. The designs based on the tree-branching rule of Leonardo da Vinci and the Hess-Murray rule were considered in addition to the constructal design. Both da Vinci and Hess-Murray designs are insensitive to the inlet velocity, and they provide better flow uniformity than the base (not tapered) design. However, the results of this paper uncover that not only pressure drop but also velocity distribution in the microdevice play an integral role in the flow uniformity. Therefore, an iterative approach was adopted with five degrees-of-freedom (inclined wall positions) and one constraint (constant distribution channel thickness) in order to uncover the constructal design which conforms the uniform flow rate distribution. In addition, the effect of slenderness of the microchannels (Svelteness) and inlet velocity on the flow rate distribution to the microchannels has been documented. This paper also uncovers that the design of a manifold should be designed with not only the consideration of pressure distribution but also dynamic pressure distribution especially for non-Svelte microdevices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, we show how the design of a microdevice manifold should be tapered for uniform flow rate distribution. The designs based on the tree-branching rule of Leonardo da Vinci and the Hess-Murray rule were considered in addition to the constructal design. Both da Vinci and Hess-Murray designs are insensitive to the inlet velocity, and they provide better flow uniformity than the base (not tapered) design. However, the results of this paper uncover that not only pressure drop but also velocity distribution in the microdevice play an integral role in the flow uniformity. Therefore, an iterative approach was adopted with five degrees-of-freedom (inclined wall positions) and one constraint (constant distribution channel thickness) in order to uncover the constructal design which conforms the uniform flow rate distribution. In addition, the effect of slenderness of the microchannels (Svelteness) and inlet velocity on the flow rate distribution to the microchannels has been documented. This paper also uncovers that the design of a manifold should be designed with not only the consideration of pressure distribution but also dynamic pressure distribution especially for non-Svelte microdevices. |
2015 |
Cetkin, Erdal Constructal Vascular Structures With High-Conductivity Inserts for Self-Cooling Journal Article JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, 137 (11), 2015, ISSN: 0022-1481. @article{ISI:000362512900008, title = {Constructal Vascular Structures With High-Conductivity Inserts for Self-Cooling}, author = {Erdal Cetkin}, doi = {10.1115/1.4030906}, issn = {0022-1481}, year = {2015}, date = {2015-11-01}, journal = {JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, volume = {137}, number = {11}, abstract = {In this paper, we show how a heat-generating domain can be cooled with embedded cooling channels and high-conductivity inserts. The volume of cooling channels and high-conductivity inserts is fixed, so is the volume of the heat-generating domain. The maximum temperature in the domain decreases with high-conductivity inserts even though the coolant volume decreases. The locations and the shapes of high-conductivity inserts corresponding to the smallest peak temperatures for different number of inserts are documented}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, we show how a heat-generating domain can be cooled with embedded cooling channels and high-conductivity inserts. The volume of cooling channels and high-conductivity inserts is fixed, so is the volume of the heat-generating domain. The maximum temperature in the domain decreases with high-conductivity inserts even though the coolant volume decreases. The locations and the shapes of high-conductivity inserts corresponding to the smallest peak temperatures for different number of inserts are documented |
Cetkin, Erdal; Oliani, Alessandro The natural emergence of asymmetric tree-shaped pathways for cooling of a non-uniformly heated domain Journal Article JOURNAL OF APPLIED PHYSICS, 118 (2), 2015, ISSN: 0021-8979. @article{ISI:000357961000033, title = {The natural emergence of asymmetric tree-shaped pathways for cooling of a non-uniformly heated domain}, author = {Erdal Cetkin and Alessandro Oliani}, doi = {10.1063/1.4926620}, issn = {0021-8979}, year = {2015}, date = {2015-07-01}, journal = {JOURNAL OF APPLIED PHYSICS}, volume = {118}, number = {2}, abstract = {Here, we show that the peak temperature on a non-uniformly heated domain can be decreased by embedding a high-conductivity insert in it. The trunk of the high-conductivity insert is in contact with a heat sink. The heat is generated non-uniformly throughout the domain or concentrated in a square spot of length scale 0.1 L-0, where L-0 is the length scale of the non-uniformly heated domain. Peak and average temperatures are affected by the volume fraction of the high-conductivity material and by the shape of the high-conductivity pathways. This paper uncovers how varying the shape of the symmetric and asymmetric high-conductivity trees affects the overall thermal conductance of the heat generating domain. The tree-shaped high-conductivity inserts tend to grow toward where the heat generation is concentrated in order to minimize the peak temperature, i.e., in order to minimize the resistances to the heat flow. This behaviour of high-conductivity trees is alike with the root growth of the plants and trees. They also tend to grow towards sunlight, and their roots tend to grow towards water and nutrients. This paper uncovers the similarity between biological trees and high-conductivity trees, which is that trees should grow asymmetrically when the boundary conditions are non-uniform. We show here even though all the trees have the same objectives (minimum flow resistance), their shape should not be the same because of the variation in boundary conditions. To sum up, this paper shows that there is a high-conductivity tree design corresponding to minimum peak temperature with fixed constraints and conditions. This result is in accord with the constructal law which states that there should be an optimal design for a given set of conditions and constraints, and this design should be morphed in order to ensure minimum flow resistances as conditions and constraints change. (c) 2015 AIP Publishing LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here, we show that the peak temperature on a non-uniformly heated domain can be decreased by embedding a high-conductivity insert in it. The trunk of the high-conductivity insert is in contact with a heat sink. The heat is generated non-uniformly throughout the domain or concentrated in a square spot of length scale 0.1 L-0, where L-0 is the length scale of the non-uniformly heated domain. Peak and average temperatures are affected by the volume fraction of the high-conductivity material and by the shape of the high-conductivity pathways. This paper uncovers how varying the shape of the symmetric and asymmetric high-conductivity trees affects the overall thermal conductance of the heat generating domain. The tree-shaped high-conductivity inserts tend to grow toward where the heat generation is concentrated in order to minimize the peak temperature, i.e., in order to minimize the resistances to the heat flow. This behaviour of high-conductivity trees is alike with the root growth of the plants and trees. They also tend to grow towards sunlight, and their roots tend to grow towards water and nutrients. This paper uncovers the similarity between biological trees and high-conductivity trees, which is that trees should grow asymmetrically when the boundary conditions are non-uniform. We show here even though all the trees have the same objectives (minimum flow resistance), their shape should not be the same because of the variation in boundary conditions. To sum up, this paper shows that there is a high-conductivity tree design corresponding to minimum peak temperature with fixed constraints and conditions. This result is in accord with the constructal law which states that there should be an optimal design for a given set of conditions and constraints, and this design should be morphed in order to ensure minimum flow resistances as conditions and constraints change. (c) 2015 AIP Publishing LLC. |
Cetkin, Erdal CONSTRUCTAL STRUCTURES FOR SELF-COOLING: MICROVASCULAR WAVY AND STRAIGHT CHANNELS Journal Article JOURNAL OF THERMAL ENGINEERING, 1 (5, 1), pp. 166-174, 2015, ISSN: 2148-7847. @article{ISI:000434616100004, title = {CONSTRUCTAL STRUCTURES FOR SELF-COOLING: MICROVASCULAR WAVY AND STRAIGHT CHANNELS}, author = {Erdal Cetkin}, doi = {10.18186/jte.10873}, issn = {2148-7847}, year = {2015}, date = {2015-02-01}, journal = {JOURNAL OF THERMAL ENGINEERING}, volume = {1}, number = {5, 1}, pages = {166-174}, abstract = {This paper shows that a conductive domain which is subjected to heating from its bottom can be cooled with embedded microvascular cooling channels in it. The volume of the domain and the coolant are fixed. The actively cooled domain is mimicked from the human skin (which regulates temperature with microvascular blood vessels). The effect of the shape of cooling channels (sinusoidal or straight) and their locations in the direction perpendicular to the bottom surface on the peak and average temperatures are studied. In addition, the effect of pressure difference in between the inlet and outlet is varied. The pressure drop in the sinusoidal channel configurations is greater than the straight channel configurations for a fixed cooling channel volume. The peak and average temperatures are the smallest with straight cooling channels located at y = 0.7 mm. Furthermore, how the cooling channel configuration should change when the heat is generated throughout the volume is studied. The peak and average temperatures are smaller with straight channels than the sinusoidal ones when the pressure drop is less than 420 Pa, and they become smaller with sinusoidal channel configurations when the pressure drop is greater than 420 Pa. In addition, the peak and average temperatures are the smallest with sinusoidal channels for a fixed flow rate. Furthermore, the peak temperatures for multiple cooling channels is documented, and the multiple channel configurations promise to the smallest peak temperature for a fixed pressure drop value. This paper uncovers that there is no optimal cooling channel design for any condition, but there is one for specific objectives and conditions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper shows that a conductive domain which is subjected to heating from its bottom can be cooled with embedded microvascular cooling channels in it. The volume of the domain and the coolant are fixed. The actively cooled domain is mimicked from the human skin (which regulates temperature with microvascular blood vessels). The effect of the shape of cooling channels (sinusoidal or straight) and their locations in the direction perpendicular to the bottom surface on the peak and average temperatures are studied. In addition, the effect of pressure difference in between the inlet and outlet is varied. The pressure drop in the sinusoidal channel configurations is greater than the straight channel configurations for a fixed cooling channel volume. The peak and average temperatures are the smallest with straight cooling channels located at y = 0.7 mm. Furthermore, how the cooling channel configuration should change when the heat is generated throughout the volume is studied. The peak and average temperatures are smaller with straight channels than the sinusoidal ones when the pressure drop is less than 420 Pa, and they become smaller with sinusoidal channel configurations when the pressure drop is greater than 420 Pa. In addition, the peak and average temperatures are the smallest with sinusoidal channels for a fixed flow rate. Furthermore, the peak temperatures for multiple cooling channels is documented, and the multiple channel configurations promise to the smallest peak temperature for a fixed pressure drop value. This paper uncovers that there is no optimal cooling channel design for any condition, but there is one for specific objectives and conditions. |
Cetkin, Erdal Constructal vascularized structures Journal Article OPEN ENGINEERING, 5 (1), pp. 220-228, 2015, ISSN: 2391-5439. @article{ISI:000218406100024, title = {Constructal vascularized structures}, author = {Erdal Cetkin}, doi = {10.1515/eng-2015-0017}, issn = {2391-5439}, year = {2015}, date = {2015-01-01}, journal = {OPEN ENGINEERING}, volume = {5}, number = {1}, pages = {220-228}, abstract = {Smart features such as self-healing and selfcooling require bathing the entire volume with a coolant or/and healing agent. Bathing the entire volume is an example of point to area (or volume) flows. Point to area flows cover all the distributing and collecting kinds of flows, i.e. inhaling and exhaling, mining, river deltas, energy distribution, distribution of products on the landscape and so on. The flow resistances of a point to area flow can be decreased by changing the design with the guidance of the constructal law, which is the law of the design evolution in time. In this paper, how the flow resistances (heat, fluid and stress) can be decreased by using the constructal law is shown with examples. First, the validity of two assumptions is surveyed: using temperature independent Hess-Murray rule and using constant diameter ducts where the duct discharges fluid along its edge. Then, point to area types of flows are explained by illustrating the results of two examples: fluid networks and heating an area. Last, how the structures should be vascularized for cooling and mechanical strength is documented. This paper shows that flow resistances can be decreased by morphing the shape freely without any restrictions or generic algorithms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Smart features such as self-healing and selfcooling require bathing the entire volume with a coolant or/and healing agent. Bathing the entire volume is an example of point to area (or volume) flows. Point to area flows cover all the distributing and collecting kinds of flows, i.e. inhaling and exhaling, mining, river deltas, energy distribution, distribution of products on the landscape and so on. The flow resistances of a point to area flow can be decreased by changing the design with the guidance of the constructal law, which is the law of the design evolution in time. In this paper, how the flow resistances (heat, fluid and stress) can be decreased by using the constructal law is shown with examples. First, the validity of two assumptions is surveyed: using temperature independent Hess-Murray rule and using constant diameter ducts where the duct discharges fluid along its edge. Then, point to area types of flows are explained by illustrating the results of two examples: fluid networks and heating an area. Last, how the structures should be vascularized for cooling and mechanical strength is documented. This paper shows that flow resistances can be decreased by morphing the shape freely without any restrictions or generic algorithms. |
Cetkin, Erdal INVERTED FINS FOR COOLING OF A NON-UNIFORMLY HEATED DOMAIN Journal Article JOURNAL OF THERMAL ENGINEERING, 1 (1), pp. 1-9, 2015, ISSN: 2148-7847. @article{ISI:000434614600001, title = {INVERTED FINS FOR COOLING OF A NON-UNIFORMLY HEATED DOMAIN}, author = {Erdal Cetkin}, doi = {10.18186/jte.12488}, issn = {2148-7847}, year = {2015}, date = {2015-01-01}, journal = {JOURNAL OF THERMAL ENGINEERING}, volume = {1}, number = {1}, pages = {1-9}, abstract = {This paper shows that the peak temperature of a non-uniformly heated region can be decreased by embedding high-conductivity tree-shaped inserts which is in contact with a heat sink from its stem. The volume fraction of the high-conductivity material is fixed, and so is the volume of the solid region. The length scale of the solid domain is L. Inside there is a cube-shaped region with length scale of 0.1L and heat production 100 times greater than the rest of the domain. The location of this hot spot was varied to uncover how its location affects the peak temperature and the design of inverted fins, i.e. highconductivity tree-shaped inserts. The volume fraction of the high-conductivity tree was varied for number of bifurcation levels of 0, 1 and 2. This showed that increasing the number of the bifurcation levels decreases the peak temperature when the volume fraction decreases. The optimal diameter ratios and optimal bifurcation angles at the each junction level are also documented. Y-shaped trees promise smaller peak temperatures than T-shaped trees. The location of the vascular tree in the z direction also affects the peak temperature when the heat generation is non-uniform. In addition, the peak temperature is minimum when z = 0.65L even though the hot spot is located on z = 0.75L.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper shows that the peak temperature of a non-uniformly heated region can be decreased by embedding high-conductivity tree-shaped inserts which is in contact with a heat sink from its stem. The volume fraction of the high-conductivity material is fixed, and so is the volume of the solid region. The length scale of the solid domain is L. Inside there is a cube-shaped region with length scale of 0.1L and heat production 100 times greater than the rest of the domain. The location of this hot spot was varied to uncover how its location affects the peak temperature and the design of inverted fins, i.e. highconductivity tree-shaped inserts. The volume fraction of the high-conductivity tree was varied for number of bifurcation levels of 0, 1 and 2. This showed that increasing the number of the bifurcation levels decreases the peak temperature when the volume fraction decreases. The optimal diameter ratios and optimal bifurcation angles at the each junction level are also documented. Y-shaped trees promise smaller peak temperatures than T-shaped trees. The location of the vascular tree in the z direction also affects the peak temperature when the heat generation is non-uniform. In addition, the peak temperature is minimum when z = 0.65L even though the hot spot is located on z = 0.75L. |
2014 |
Cetkin, Erdal Three-dimensional high-conductivity trees for volumetric cooling Journal Article INTERNATIONAL JOURNAL OF ENERGY RESEARCH, 38 (12), pp. 1571-1577, 2014, ISSN: 0363-907X. @article{ISI:000342133500008, title = {Three-dimensional high-conductivity trees for volumetric cooling}, author = {Erdal Cetkin}, doi = {10.1002/er.3176}, issn = {0363-907X}, year = {2014}, date = {2014-10-01}, journal = {INTERNATIONAL JOURNAL OF ENERGY RESEARCH}, volume = {38}, number = {12}, pages = {1571-1577}, abstract = {Here, we show how the cooling performance of a volumetrically heated solid can be increased by embedding high-conductivity tree-shaped designs in it. The volume fraction occupied by the high-conductivity material is fixed. Embedding the high-conductivity material as trees in the solid decreases the maximum temperature more than three times compared with distributing the high-conductivity material uniformly throughout the solid. The maximum temperature decreases as the number of the bifurcation levels and the volume fraction of the highly conductive material increase. The thermal resistance of the cube is the lowest when the diameter ratio of the mother and daughter branches at each pairing junction is 2. Changing from T-shaped to Y-shaped designs and from two-dimensional to three-dimensional designs decrease the maximum and the volume averaged temperatures. The peak temperature is the lowest in three-dimensional and Y-shaped designs. This paper shows that the peak temperature of the heated solid can be decreased by only varying the shape of the high-conductivity tree embedded in it. Copyright (c) 2014 John Wiley & Sons, Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here, we show how the cooling performance of a volumetrically heated solid can be increased by embedding high-conductivity tree-shaped designs in it. The volume fraction occupied by the high-conductivity material is fixed. Embedding the high-conductivity material as trees in the solid decreases the maximum temperature more than three times compared with distributing the high-conductivity material uniformly throughout the solid. The maximum temperature decreases as the number of the bifurcation levels and the volume fraction of the highly conductive material increase. The thermal resistance of the cube is the lowest when the diameter ratio of the mother and daughter branches at each pairing junction is 2. Changing from T-shaped to Y-shaped designs and from two-dimensional to three-dimensional designs decrease the maximum and the volume averaged temperatures. The peak temperature is the lowest in three-dimensional and Y-shaped designs. This paper shows that the peak temperature of the heated solid can be decreased by only varying the shape of the high-conductivity tree embedded in it. Copyright (c) 2014 John Wiley & Sons, Ltd. |
Cetkin, Erdal EMERGENCE OF TAPERED DUCTS IN VASCULAR DESIGNS WITH LAMINAR AND TURBULENT FLOWS Journal Article JOURNAL OF POROUS MEDIA, 17 (8), pp. 715-722, 2014, ISSN: 1091-028X. @article{ISI:000342967400005, title = {EMERGENCE OF TAPERED DUCTS IN VASCULAR DESIGNS WITH LAMINAR AND TURBULENT FLOWS}, author = {Erdal Cetkin}, doi = {10.1615/JPorMedia.v17.i8.50}, issn = {1091-028X}, year = {2014}, date = {2014-01-01}, journal = {JOURNAL OF POROUS MEDIA}, volume = {17}, number = {8}, pages = {715-722}, abstract = {Here we show that tapered ducts emerge in volumetrically bathed porous materials to decrease the resistance to the flow in laminar and turbulent flow regimes. The fluid enters the volume from one point and it is distributed to the entire volume. After bathing the volume, it is collected and leaves the volume from another point, i.e., two trees matched canopy to canopy. This paper shows that the flow architecture (i.e., design of the void spaces in a porous material) should be changed to obtain the minimum resistance to the flow as its size increases. Tapering the ducts decreases the order of the transition size, i.e., the size for changing from one construct to another to obtain the minimum pressure drop. The decrease in the pressure drop is 16% and 38% with the tapered ducts when the flow is laminar and turbulent, respectively. In addition, the volume ratios and the shape of the tapered ducts are documented. There is no design existing in nature with diameters of constant size in order to distribute and/or collect heat, fluid, and/or stress such as bones, rivers, veins, and tree branches. The emergence of the tapered ducts in designed porous materials is natural.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here we show that tapered ducts emerge in volumetrically bathed porous materials to decrease the resistance to the flow in laminar and turbulent flow regimes. The fluid enters the volume from one point and it is distributed to the entire volume. After bathing the volume, it is collected and leaves the volume from another point, i.e., two trees matched canopy to canopy. This paper shows that the flow architecture (i.e., design of the void spaces in a porous material) should be changed to obtain the minimum resistance to the flow as its size increases. Tapering the ducts decreases the order of the transition size, i.e., the size for changing from one construct to another to obtain the minimum pressure drop. The decrease in the pressure drop is 16% and 38% with the tapered ducts when the flow is laminar and turbulent, respectively. In addition, the volume ratios and the shape of the tapered ducts are documented. There is no design existing in nature with diameters of constant size in order to distribute and/or collect heat, fluid, and/or stress such as bones, rivers, veins, and tree branches. The emergence of the tapered ducts in designed porous materials is natural. |
Res. Assist. Dr. Murat Demirel
Educational Background
B.Sc. İzmir Institute of Technology, Mechanical Engineering, 2015
M.Sc. İzmir Institute of Technology, Mechanical Engineering, 2018
Ph.D. İzmir Institute of Technology, Mechanical Engineering, 2025
Research Interests
- Mechanism Science
- Cable-constrained Parallel Manipulators
- Deployable Structures
- +90 232 750 6752
- +90 232 750 6701
- Mechanical Engineering Building, Rasim Alizade Mechatronics Lab. (Z31)
Publications
2023 |
Demirel, Murat; Kiper, Gökhan; Carbone, Giuseppe; Ceccarelli, Marco Design of a novel hybrid cable-constrained parallel leg mechanism for biped walking machines Journal Article Robotica, 41 (6), pp. 1778 – 1793, 2023, (All Open Access, Green Open Access). @article{Demirel20231778, title = {Design of a novel hybrid cable-constrained parallel leg mechanism for biped walking machines}, author = {Murat Demirel and Gökhan Kiper and Giuseppe Carbone and Marco Ceccarelli}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85182028851&doi=10.1017%2fS0263574723000140&partnerID=40&md5=60745b93d1c9dbaf0d172fdcc365338f}, doi = {10.1017/S0263574723000140}, year = {2023}, date = {2023-01-01}, journal = {Robotica}, volume = {41}, number = {6}, pages = {1778 – 1793}, abstract = {In this paper, a novel cable-constrained parallel mechanism is presented as a lightweight, low-cost leg mechanism design for walking machines to be used on flat surfaces. The proposed leg mechanism has three translational degrees of freedom. It is based on two specific hybrid kinematic topologies being herewith proposed. The paper reports the kinematic analysis formulation and a position performance evaluation to confirm the main characteristics of the proposed solutions. A 3D CAD model and simulations are carried out to demonstrate the feasibility of the proposed design for performing a human-like gait trajectory. A prototype has been built, and preliminarily tests have been conducted to confirm the motion capabilities of the proposed mechanism design. Then a second, enhanced prototype has been designed and built. An experimental validation is carried out for tracking a planar walking trajectory with the built prototypes by using a real-time PCI controller. Results are presented to validate the operation characteristics of the proposed mechanism and to prove its feasibility for legged walking machines. © The Author(s), 2023.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a novel cable-constrained parallel mechanism is presented as a lightweight, low-cost leg mechanism design for walking machines to be used on flat surfaces. The proposed leg mechanism has three translational degrees of freedom. It is based on two specific hybrid kinematic topologies being herewith proposed. The paper reports the kinematic analysis formulation and a position performance evaluation to confirm the main characteristics of the proposed solutions. A 3D CAD model and simulations are carried out to demonstrate the feasibility of the proposed design for performing a human-like gait trajectory. A prototype has been built, and preliminarily tests have been conducted to confirm the motion capabilities of the proposed mechanism design. Then a second, enhanced prototype has been designed and built. An experimental validation is carried out for tracking a planar walking trajectory with the built prototypes by using a real-time PCI controller. Results are presented to validate the operation characteristics of the proposed mechanism and to prove its feasibility for legged walking machines. © The Author(s), 2023. |
Assoc. Prof. Dr. Mehmet Dördüncü
Educational Background
B.Sc. Erciyes University, Turkey, Mechanical Engineering, 2011
M.Sc. Erciyes University, Turkey, Mechanical Engineering, 2013
Ph.D. University of Arizona, USA, Mechanical Engineering, 2018
Research Interests
- Mechanical Behaviors of Materials, Computational Mechanics
- Peridynamics
- Fracture Mechanics
- Composite Materials
- +90 232 750 6784
- +90 232 750 6701
- Mechanical Engineering Building (Z17)
Publications
2025 |
Kaya, Kadir; Dorduncu, Mehmet; Madenci, Erdogan Variable horizon ordinary state-based peridynamic analysis in ANSYS framework Journal Article 32 (9), pp. 2079 – 2095, 2025. @article{Kaya20252079, title = {Variable horizon ordinary state-based peridynamic analysis in ANSYS framework}, author = {Kadir Kaya and Mehmet Dorduncu and Erdogan Madenci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-105003130694&doi=10.1080%2f15376494.2024.2375028&partnerID=40&md5=938c5055b09ddffbf4be1624b74b799d}, doi = {10.1080/15376494.2024.2375028}, year = {2025}, date = {2025-01-01}, volume = {32}, number = {9}, pages = {2079 – 2095}, abstract = {This study presents the implementation of ordinary state-based peridynamic (OSB PD) analysis in a finite element framework using ANSYS, a commercial software. The novelty of the present PD formulation is its ability to accommodate nonuniform discretization of the PD solution domain, which may be crucial for the realistic modeling of complex structures. It enables the use of variable horizon while eliminating the need for surface and volumetric correction procedures. The PD governing equations are constructed by using MATRIX27, an element native to ANSYS. The PD bond breakage during the implicit solution of these equations is achieved through the EKILL option in ANSYS. The efficacy and robustness of the present PD approach are demonstrated by considering four distinct geometric configurations, each subjected to specific boundary conditions. The results from the present PD approach exhibit a good agreement with those obtained from traditional finite element method (FEM) and experimental data. © 2024 Taylor & Francis Group, LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study presents the implementation of ordinary state-based peridynamic (OSB PD) analysis in a finite element framework using ANSYS, a commercial software. The novelty of the present PD formulation is its ability to accommodate nonuniform discretization of the PD solution domain, which may be crucial for the realistic modeling of complex structures. It enables the use of variable horizon while eliminating the need for surface and volumetric correction procedures. The PD governing equations are constructed by using MATRIX27, an element native to ANSYS. The PD bond breakage during the implicit solution of these equations is achieved through the EKILL option in ANSYS. The efficacy and robustness of the present PD approach are demonstrated by considering four distinct geometric configurations, each subjected to specific boundary conditions. The results from the present PD approach exhibit a good agreement with those obtained from traditional finite element method (FEM) and experimental data. © 2024 Taylor & Francis Group, LLC. |
2024 |
Altay, Ugur; Dorduncu, Mehmet; Kadioglu, Suat Dual Horizon Peridynamic Approach for Studying the Effect of Porous Media on the Dynamic Crack Growth in Brittle Materials Journal Article 6 (3), pp. 505 – 529, 2024. @article{Altay2024505, title = {Dual Horizon Peridynamic Approach for Studying the Effect of Porous Media on the Dynamic Crack Growth in Brittle Materials}, author = {Ugur Altay and Mehmet Dorduncu and Suat Kadioglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85183743190&doi=10.1007%2fs42102-023-00115-7&partnerID=40&md5=7fef73281ee9fdebd3c3d2bf8addb867}, doi = {10.1007/s42102-023-00115-7}, year = {2024}, date = {2024-01-01}, volume = {6}, number = {3}, pages = {505 – 529}, abstract = {This study aims to investigate the effect of the stop-hole configurations on dynamic cracks using the dual-horizon peridynamic approach (DHPD). The traditional PD formulations require uniform discretization for the solution domain. Therefore, to investigate the effect of the stop holes with traditional PD, more densely spaced points are used to represent the holes. If less densely spaced points are used in traditional PD, this may lead to unexpected crack initiations around the stop holes due to stress concentrations originating from the stair-step-like shapes. If non-uniform point spacing is used for representing the outer edge of the stop hole accurately in traditional PD, a ghost force problem may occur and the forces of the points in the bond may not interact in pairs. Moreover, the use of fine mesh causes high computational efforts. Therefore, the DHPD, which allows non-uniform point spacings unlike traditional PD, is employed for examining the characteristics of dynamic crack propagation in the presence of stop holes. Before stop-hole configurations are examined, the developed DHPD code is validated with the results of a reference solution belonging to the Kalthoff-Winkler test. After the validation process for the DHPD code is successfully completed, the crack paths in the stop hole configurations obtained by DHPD are compared with the experiments, and a good agreement between the test and PD simulation is achieved. Furthermore, the performances of the stop hole configurations are investigated by DHPD in terms of toughening effect on the brittle material. Besides, the effect of crack branching on dynamic crack retardation is also examined. The results of dynamic crack propagation simulated by DHPD are compared with the experimental observations and reference results. The results of DHPD are observed to be a good agreement with the experimental observations available in the existing literature. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study aims to investigate the effect of the stop-hole configurations on dynamic cracks using the dual-horizon peridynamic approach (DHPD). The traditional PD formulations require uniform discretization for the solution domain. Therefore, to investigate the effect of the stop holes with traditional PD, more densely spaced points are used to represent the holes. If less densely spaced points are used in traditional PD, this may lead to unexpected crack initiations around the stop holes due to stress concentrations originating from the stair-step-like shapes. If non-uniform point spacing is used for representing the outer edge of the stop hole accurately in traditional PD, a ghost force problem may occur and the forces of the points in the bond may not interact in pairs. Moreover, the use of fine mesh causes high computational efforts. Therefore, the DHPD, which allows non-uniform point spacings unlike traditional PD, is employed for examining the characteristics of dynamic crack propagation in the presence of stop holes. Before stop-hole configurations are examined, the developed DHPD code is validated with the results of a reference solution belonging to the Kalthoff-Winkler test. After the validation process for the DHPD code is successfully completed, the crack paths in the stop hole configurations obtained by DHPD are compared with the experiments, and a good agreement between the test and PD simulation is achieved. Furthermore, the performances of the stop hole configurations are investigated by DHPD in terms of toughening effect on the brittle material. Besides, the effect of crack branching on dynamic crack retardation is also examined. The results of dynamic crack propagation simulated by DHPD are compared with the experimental observations and reference results. The results of DHPD are observed to be a good agreement with the experimental observations available in the existing literature. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024. |
Altay, Ugur; Dorduncu, Mehmet; Kadioglu, Suat; Madenci, Erdogan Bond-based peridynamic fatigue analysis of ductile materials with Neuber’s plasticity correction Journal Article 2024. @article{Altay2024b, title = {Bond-based peridynamic fatigue analysis of ductile materials with Neuber’s plasticity correction}, author = {Ugur Altay and Mehmet Dorduncu and Suat Kadioglu and Erdogan Madenci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85211816909&doi=10.1007%2fs00366-024-02092-x&partnerID=40&md5=2240d6576d9f33275e71aa7b1761aeeb}, doi = {10.1007/s00366-024-02092-x}, year = {2024}, date = {2024-01-01}, abstract = {This study introduces an approach for performing bond-based (BB) peridynamic (PD) fatigue analysis of ductile materials. Existing BB PD fatigue models do not account for the effect of plastic deformation. The current approach addresses this by incorporating Neuber’s plasticity correction concept into the fatigue model. Neuber’s correction adjusts the stress and strain predictions of the PD elastic solution to account for local plastic deformation around crack tips. The PD fatigue simulations demonstrate the effectiveness of this method and improvements in fatigue life predictions by considering local plasticity effects. The numerical results first examine the response of a ductile plate without a crack under quasi-static monotonic loading. Subsequently, specimens exhibiting Mode I and mixed-mode crack propagation paths due to cyclic loading are analyzed. The PD predictions accurately capture the test data. Additionally, the model specifically investigates the effect of a stop hole on fatigue life. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study introduces an approach for performing bond-based (BB) peridynamic (PD) fatigue analysis of ductile materials. Existing BB PD fatigue models do not account for the effect of plastic deformation. The current approach addresses this by incorporating Neuber’s plasticity correction concept into the fatigue model. Neuber’s correction adjusts the stress and strain predictions of the PD elastic solution to account for local plastic deformation around crack tips. The PD fatigue simulations demonstrate the effectiveness of this method and improvements in fatigue life predictions by considering local plasticity effects. The numerical results first examine the response of a ductile plate without a crack under quasi-static monotonic loading. Subsequently, specimens exhibiting Mode I and mixed-mode crack propagation paths due to cyclic loading are analyzed. The PD predictions accurately capture the test data. Additionally, the model specifically investigates the effect of a stop hole on fatigue life. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2024. |
Muscati, Isra Al; Jahwari, Farooq Al; Pervez, Tasneem; Dorduncu, Mehmet 31 (30), pp. 13488 – 13501, 2024. @article{AlMuscati202413488, title = {Molecular dynamics investigation for mechanical and failure behaviors of carbon nanotube-reinforced functionally graded aluminum–copper nanocomposites}, author = {Isra Al Muscati and Farooq Al Jahwari and Tasneem Pervez and Mehmet Dorduncu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85175376208&doi=10.1080%2f15376494.2023.2273009&partnerID=40&md5=aa916605310c90a9405b4a75e7a0df0a}, doi = {10.1080/15376494.2023.2273009}, year = {2024}, date = {2024-01-01}, volume = {31}, number = {30}, pages = {13488 – 13501}, abstract = {In this study, molecular dynamics simulation is carried out to investigate the mechanical properties and failure behavior of a novel carbon nanotube-reinforced aluminum-copper alloy nanocomposite (Al–Cu/CNT). The study explores the influence of several key parameters, including the volume fraction of the carbon nanotubes (CNT), the diameter of CNT, the structure (zigzag, armchair, and chiral) of CNT, and the applied strain rate on the mechanical behavior of Al–Cu /CNT nanocomposite structure. The MD simulation results reveal that increasing the volume fraction of the CNT evidently increases the modulus of elasticity whereas it has no detrimental effect on the failure strain levels of the nanocomposites. The size of the CNT exhibits an inverse relationship with the elastic modulus. It is noted that increasing the size of the armchair CNTs results in lower elastic modulus levels and higher failure strain levels. The failure behavior of the Al–Cu /CNT nanocomposite is observed to vary according to the structure of the CNT. The nanostructure with zigzag CNTs experiences a gradual failure mode whilst armchair CNTs lead to a sudden failure in the nanostructures. The applied strain rate plays a minor role on the elastic modulus, but a slight increase in failure strain levels is observed at higher strain rates. The mechanical behavior of functionally graded Al–Cu alloy reinforced with CNT is also investigated (Al–Cu FGM/CNT). Minor changes are noticed in the elastic modulus and the failure strain levels of Al–Cu FGM/CNT with different material variations. © 2023 Taylor & Francis Group, LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, molecular dynamics simulation is carried out to investigate the mechanical properties and failure behavior of a novel carbon nanotube-reinforced aluminum-copper alloy nanocomposite (Al–Cu/CNT). The study explores the influence of several key parameters, including the volume fraction of the carbon nanotubes (CNT), the diameter of CNT, the structure (zigzag, armchair, and chiral) of CNT, and the applied strain rate on the mechanical behavior of Al–Cu /CNT nanocomposite structure. The MD simulation results reveal that increasing the volume fraction of the CNT evidently increases the modulus of elasticity whereas it has no detrimental effect on the failure strain levels of the nanocomposites. The size of the CNT exhibits an inverse relationship with the elastic modulus. It is noted that increasing the size of the armchair CNTs results in lower elastic modulus levels and higher failure strain levels. The failure behavior of the Al–Cu /CNT nanocomposite is observed to vary according to the structure of the CNT. The nanostructure with zigzag CNTs experiences a gradual failure mode whilst armchair CNTs lead to a sudden failure in the nanostructures. The applied strain rate plays a minor role on the elastic modulus, but a slight increase in failure strain levels is observed at higher strain rates. The mechanical behavior of functionally graded Al–Cu alloy reinforced with CNT is also investigated (Al–Cu FGM/CNT). Minor changes are noticed in the elastic modulus and the failure strain levels of Al–Cu FGM/CNT with different material variations. © 2023 Taylor & Francis Group, LLC. |
Ermis, Merve; Dorduncu, Mehmet; Kutlu, Akif Peridynamic differential operator for stress analysis of imperfect functionally graded porous sandwich beams based on refined zigzag theory Journal Article 133 , pp. 414 – 435, 2024. @article{Ermis2024414, title = {Peridynamic differential operator for stress analysis of imperfect functionally graded porous sandwich beams based on refined zigzag theory}, author = {Merve Ermis and Mehmet Dorduncu and Akif Kutlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85195067189&doi=10.1016%2fj.apm.2024.05.032&partnerID=40&md5=5926ec78dbfe86cc1ce3ae24e34e333e}, doi = {10.1016/j.apm.2024.05.032}, year = {2024}, date = {2024-01-01}, volume = {133}, pages = {414 – 435}, abstract = {This study focuses on the stress analysis of imperfect functionally graded porous (FGP) sandwich beams using the Peridynamic Differential Operator (PDDO) and Refined Zigzag Theory (RZT). Functionally graded materials (FGMs) can be found in diverse engineering applications since they offer smooth transitions in the mechanical properties of distinct materials, unlike traditional composite materials. Micro-voids and porosities may appear inside the FGMs due to technical challenges during the manufacturing process of such materials. Therefore, understanding the stress variations of the FG sandwich beams with porosities/micro-voids, which are called imperfect FGMs, under loads is of vital importance. In order to achieve the porous configuration in the FG structures, the modified rule of mixtures is applied to calculate the effective material properties of FGMs. The RZT is very suitable for stress analysis of laminated composites, especially for thick and moderately thick beams. It contains only four kinematic variables and eliminates the use of the shear correction factors. In this study, the equilibrium equations of the RZT are solved by means of the PDDO for the stress analysis of imperfect FG sandwich beams having uniform and non-uniform porosity distributions. The PDDO transforms the differential equations into their nonlocal form, namely integral form, providing highly accurate approximations of the derivatives. A comprehensive PDDO analysis is performed for the investigation of the influence of the material variation, and even and uneven porosity distributions on the stress variations of the imperfect FG sandwich beams. It is noted that when the FG core exhibits soft material distributions, the effect of porosity is evident. The even type porosity distribution pattern is more influential on the axial displacement and stress variations in comparison with those of the uneven type porosity distribution pattern. © 2024 Elsevier Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study focuses on the stress analysis of imperfect functionally graded porous (FGP) sandwich beams using the Peridynamic Differential Operator (PDDO) and Refined Zigzag Theory (RZT). Functionally graded materials (FGMs) can be found in diverse engineering applications since they offer smooth transitions in the mechanical properties of distinct materials, unlike traditional composite materials. Micro-voids and porosities may appear inside the FGMs due to technical challenges during the manufacturing process of such materials. Therefore, understanding the stress variations of the FG sandwich beams with porosities/micro-voids, which are called imperfect FGMs, under loads is of vital importance. In order to achieve the porous configuration in the FG structures, the modified rule of mixtures is applied to calculate the effective material properties of FGMs. The RZT is very suitable for stress analysis of laminated composites, especially for thick and moderately thick beams. It contains only four kinematic variables and eliminates the use of the shear correction factors. In this study, the equilibrium equations of the RZT are solved by means of the PDDO for the stress analysis of imperfect FG sandwich beams having uniform and non-uniform porosity distributions. The PDDO transforms the differential equations into their nonlocal form, namely integral form, providing highly accurate approximations of the derivatives. A comprehensive PDDO analysis is performed for the investigation of the influence of the material variation, and even and uneven porosity distributions on the stress variations of the imperfect FG sandwich beams. It is noted that when the FG core exhibits soft material distributions, the effect of porosity is evident. The even type porosity distribution pattern is more influential on the axial displacement and stress variations in comparison with those of the uneven type porosity distribution pattern. © 2024 Elsevier Inc. |
Yurtsever, Batuhan; Bab, Yonca; Kutlu, Akif; Dorduncu, Mehmet A new C0 continuous refined zigzag 1,2 finite element formulation for flexural and free vibration analyses of laminated composite beams Journal Article 331 , 2024. @article{Yurtsever2024, title = {A new C0 continuous refined zigzag 1,2 finite element formulation for flexural and free vibration analyses of laminated composite beams}, author = {Batuhan Yurtsever and Yonca Bab and Akif Kutlu and Mehmet Dorduncu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85182029045&doi=10.1016%2fj.compstruct.2024.117890&partnerID=40&md5=039fc39944c0a538ae2d8b888fd1f117}, doi = {10.1016/j.compstruct.2024.117890}, year = {2024}, date = {2024-01-01}, volume = {331}, abstract = {This study presents a novel C0 continuous refined zigzag finite element formulation 1,2, namely RZE1,2, for the bending and free vibration analyses of laminated composite beams. The Refined Zigzag Theory (RZT) effectively combines accuracy and computational efficiency, making it a robust approach for thin and thick laminated composite structures. The RZT eliminates the need for shear correction factors, thereby enhancing the overall streamline of the analysis process. The present RZE1,2 formulation takes into account the transverse stretching by introducing quadratic through-thickness variations of deflection components. The governing equations of the RZT are derived by means of Hamilton's principle. The through-the-thickness variations of the transverse shear and normal stresses are calculated by integrating the stress equilibrium equations in a post-processing step. Therefore, the Peridynamic Least Squares Minimization (PDLSM) approach is utilized to obtain precise derivatives of axial stresses in the stress equilibrium equations. A new finite element formulation is built up with 3-nodes with a total of 15 DOF. In order to study the influence of transverse stretching, different types of boundary conditions and material variations are applied for laminated composite beams for the bending and free vibration analyses. The distribution of displacements as well as the axial and transverse stresses of the thick beams are extensively examined. The outcomes of RZT are in good agreement with the reference solutions in the literature. The findings of the present study reveal that the presence of the transverse stretching produces more realistic predictions for thick beams where the shear deformations are influential. © 2024 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study presents a novel C0 continuous refined zigzag finite element formulation 1,2, namely RZE1,2, for the bending and free vibration analyses of laminated composite beams. The Refined Zigzag Theory (RZT) effectively combines accuracy and computational efficiency, making it a robust approach for thin and thick laminated composite structures. The RZT eliminates the need for shear correction factors, thereby enhancing the overall streamline of the analysis process. The present RZE1,2 formulation takes into account the transverse stretching by introducing quadratic through-thickness variations of deflection components. The governing equations of the RZT are derived by means of Hamilton's principle. The through-the-thickness variations of the transverse shear and normal stresses are calculated by integrating the stress equilibrium equations in a post-processing step. Therefore, the Peridynamic Least Squares Minimization (PDLSM) approach is utilized to obtain precise derivatives of axial stresses in the stress equilibrium equations. A new finite element formulation is built up with 3-nodes with a total of 15 DOF. In order to study the influence of transverse stretching, different types of boundary conditions and material variations are applied for laminated composite beams for the bending and free vibration analyses. The distribution of displacements as well as the axial and transverse stresses of the thick beams are extensively examined. The outcomes of RZT are in good agreement with the reference solutions in the literature. The findings of the present study reveal that the presence of the transverse stretching produces more realistic predictions for thick beams where the shear deformations are influential. © 2024 Elsevier Ltd |
Res. Assist. Dr. Timuçin Eriş
Educational Background
B.Sc. Gazi University, Mechanical Engineering, 1991
M.Sc. Illinois Institute of Technology, Mechanical Engineering, 1997
Ph.D. Dokuz Eylül University, Mechanical Engineering, 2008
Research Interests
- Control Systems
- Artificial Neural Networks
- Finite Elements
- +90 232 750 6790
- +90 232 750 6701
- Mechanical Engineering Building (203, 2nd floor)
Res. Assist. Dr. İbrahimcan Görgülü
Educational Background
B.Sc. Gediz University, Mechanical Engineering, 2015
M.Sc. İzmir Institute of Technology, Mechanical Engineering, 2018
Ph.D. İzmir Institute of Technology, Mechanical Engineering, 2025
Research Interests
- Haptics
- Stiffness
- Control
- +90 232 750 6795
- +90 232 750 6701
- Mechanical Engineering Building, Human-Robot Interaction Lab. (Z56)
Publications
2025 |
Görgülü, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gökhan A new safe flexible torsion joint design with softening stiffness characteristics Journal Article 210 , 2025. @article{Görgülü2025, title = {A new safe flexible torsion joint design with softening stiffness characteristics}, author = {Ibrahimcan Görgülü and Mehmet Ismet Can Dede and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-105001995877&doi=10.1016%2fj.mechmachtheory.2025.106015&partnerID=40&md5=cfbbf7366b96aa9e72999c51346475de}, doi = {10.1016/j.mechmachtheory.2025.106015}, year = {2025}, date = {2025-01-01}, volume = {210}, abstract = {This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025 |
2023 |
Gorgulu, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gokhan Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism Journal Article MECHANISM AND MACHINE THEORY, 185 , 2023. @article{WOS:000966404700001, title = {Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism}, author = {Ibrahimcan Gorgulu and Mehmet Ismet Can Dede and Gokhan Kiper}, doi = {10.1016/j.mechmachtheory.2023.105343}, year = {2023}, date = {2023-07-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {185}, abstract = {Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results. |
2020 |
Gorgulu, Ibrahimcan; Carbone, Giuseppe; Dede, Can M I Time efficient stiffness model computation for a parallel haptic mechanism via the virtual joint method Journal Article MECHANISM AND MACHINE THEORY, 143 , 2020, ISSN: 0094-114X. @article{ISI:000502050800019, title = {Time efficient stiffness model computation for a parallel haptic mechanism via the virtual joint method}, author = {Ibrahimcan Gorgulu and Giuseppe Carbone and Can M I Dede}, doi = {10.1016/j.mechmachtheory.2019.103614}, issn = {0094-114X}, year = {2020}, date = {2020-01-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {143}, abstract = {Haptic devices are used for displaying a range of mechanical impedance values to the user. This impedance is regulated by a real-time control loop depending on the position information of the end-effector, which is usually acquired indirectly by using forward kinematics equations. Nevertheless, the kinematic model is insufficient to obtain accurate values if there are non-negligible compliant displacements. This gives a strong motivation for implementing a real-time stiffness model in the haptic control loop for improving its accuracy. Additionally, stiffness performance indices can be used at the design stage for enhancing the haptic devices impedance range within optimal design procedures. Fast solutions of a stiffness model are required for a real-time control as well as for decreasing the optimization time during a design process with a trade-off between accuracy and computational costs. In this study, we propose a computation time-efficient stiffness analysis of a parallel haptic device mechanism. The accuracy and computational costs of the proposed model are calculated and compared with a model that is obtained via a finite element method to demonstrate the effectiveness of the proposed approach with the desired real-time and accuracy performance. (C) 2019 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Haptic devices are used for displaying a range of mechanical impedance values to the user. This impedance is regulated by a real-time control loop depending on the position information of the end-effector, which is usually acquired indirectly by using forward kinematics equations. Nevertheless, the kinematic model is insufficient to obtain accurate values if there are non-negligible compliant displacements. This gives a strong motivation for implementing a real-time stiffness model in the haptic control loop for improving its accuracy. Additionally, stiffness performance indices can be used at the design stage for enhancing the haptic devices impedance range within optimal design procedures. Fast solutions of a stiffness model are required for a real-time control as well as for decreasing the optimization time during a design process with a trade-off between accuracy and computational costs. In this study, we propose a computation time-efficient stiffness analysis of a parallel haptic device mechanism. The accuracy and computational costs of the proposed model are calculated and compared with a model that is obtained via a finite element method to demonstrate the effectiveness of the proposed approach with the desired real-time and accuracy performance. (C) 2019 Elsevier Ltd. All rights reserved. |
Prof. Dr. Mustafa Güden
Educational Background
B.Sc. Middle East Technical University, Turkey, Metallurgical and Materials Engineering, 1989
M.Sc. Middle East Technical University, Turkey, Metallurgical and Materials Engineering, 1992
Ph.D. University of Delaware, USA, Materials Science and Engineering, 1999
Research Interests
- Composite materials (Carbon and glass fiber reinforced and nano silica reinforced epoxy matrix composites, ceramic fiber and particulate reinforced aluminum and magnesium matrix composites, ceramic-ceramic composites): processing, static and dynamic testing and dynamic mechanical deformation numerical modelling (Ls-DYNA, Mat 162)
- Cellular and lattice structures (Aluminum foams, honeycomb and corrugated structures, Titanium foams, cellular concrete and glass foams): processing, dynamic testing and dynamic mechanical deformation numerical modelling
- Additive manufacturing (316 L Stainless Steel and Ti64)
- (4) Dynamic testing (Split Hopkinson Pressure Bar and Direct impact and Taylor impact tests): test and numerical and analytical modelling;
- Mechanical behavior of materials and
- Microstructure-mechanical property relations
- +90 232 750 6779
- +90 232 750 6701
- Mechanical Engineering Building (Z10)
Publications
2025 |
Erten, H İ; Çimen, G; Yıldıztekin, F M; Güden, M Analysis and Comparison of the Projectile Impact Response of an Electron Beam Melt-Ti64 Body Centered Cubic Lattice-Cored Sandwich Plate Journal Article 2025. @article{Erten2025, title = {Analysis and Comparison of the Projectile Impact Response of an Electron Beam Melt-Ti64 Body Centered Cubic Lattice-Cored Sandwich Plate}, author = {H İ Erten and G Çimen and F M Yıldıztekin and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85217163382&doi=10.1007%2fs11340-025-01150-9&partnerID=40&md5=85bf408e4746b784c64e57acb0edd288}, doi = {10.1007/s11340-025-01150-9}, year = {2025}, date = {2025-01-01}, abstract = {Background: One potential application of additively fabricated lattice structures is in the blade containment rings of gas turbine engines. The blade containment rings are expected to be able to absorb the kinetic energy of a released blade (broken blade) in order to protect the engine parts from damaging. Metallic lattice-cored sandwich plates provide a gap (free space) between two face sheets, which helps to arrest the released blade and increases the energy absorption capability of containment rings. Objective: The objective was to investigate numerically the projectile impact response of Body-Centered-Cubic (BCC) Electron-Beam-Melt (EBM) lattice-cored/Ti64 face sheet sandwich plates as compared with that of an equal-mass monolithic EBM-Ti64 plate. Methods: The projectile impact simulations were implemented in LS-DYNA using the previously determined flow stress and damage models and a spherical steel impactor at the velocities ranging from 150 to 500 m s−1. The experimental projectile impact tests on the monolithic plate were performed at two different impact velocities and the results were used to confirm the validity of the used flow stress and damage models for the monolithic plate models. Results: Lower impact stresses were found numerically in the sandwich plate as compared with the monolithic plate at the same impact velocity. The bending and multi-cracking of the struts over a wide area in the sandwich plate increased the energy absorption and resulted in the arrest of the projectile at relatively high velocities. While monolithic plate exhibited a local bent area, resulting in the development of high tensile stresses and the projectile perforations at lower velocities. Conclusions: The numerical impact stresses in the sandwich plate were distributed over a wider area around the projectile, leading to the fracture and bending of many individual struts which significantly increased the resistance to the perforation. Hence, the investigated lattice cell topology and cell, strut, and face sheet sizes and the lattice-cored sandwich plate was shown potentially more successful in stopping the projectiles than the equal-mass monolithic plates. © The Author(s) 2025.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: One potential application of additively fabricated lattice structures is in the blade containment rings of gas turbine engines. The blade containment rings are expected to be able to absorb the kinetic energy of a released blade (broken blade) in order to protect the engine parts from damaging. Metallic lattice-cored sandwich plates provide a gap (free space) between two face sheets, which helps to arrest the released blade and increases the energy absorption capability of containment rings. Objective: The objective was to investigate numerically the projectile impact response of Body-Centered-Cubic (BCC) Electron-Beam-Melt (EBM) lattice-cored/Ti64 face sheet sandwich plates as compared with that of an equal-mass monolithic EBM-Ti64 plate. Methods: The projectile impact simulations were implemented in LS-DYNA using the previously determined flow stress and damage models and a spherical steel impactor at the velocities ranging from 150 to 500 m s−1. The experimental projectile impact tests on the monolithic plate were performed at two different impact velocities and the results were used to confirm the validity of the used flow stress and damage models for the monolithic plate models. Results: Lower impact stresses were found numerically in the sandwich plate as compared with the monolithic plate at the same impact velocity. The bending and multi-cracking of the struts over a wide area in the sandwich plate increased the energy absorption and resulted in the arrest of the projectile at relatively high velocities. While monolithic plate exhibited a local bent area, resulting in the development of high tensile stresses and the projectile perforations at lower velocities. Conclusions: The numerical impact stresses in the sandwich plate were distributed over a wider area around the projectile, leading to the fracture and bending of many individual struts which significantly increased the resistance to the perforation. Hence, the investigated lattice cell topology and cell, strut, and face sheet sizes and the lattice-cored sandwich plate was shown potentially more successful in stopping the projectiles than the equal-mass monolithic plates. © The Author(s) 2025. |
2024 |
Güden, Mustafa; Betin, Bahattin Berkan; Heptepe, Cafer Can; Güleç, Efe Batı; Yağcı, Yavuz Emre; Figen, Aysel Kantürk; Filiz, Bilge Coşkuner The compaction behavior of Magnesium-Expanded Natural Graphite powder mixtures: Tensile strengths of compacted pellets Journal Article 377 , 2024. @article{Güden2024, title = {The compaction behavior of Magnesium-Expanded Natural Graphite powder mixtures: Tensile strengths of compacted pellets}, author = {Mustafa Güden and Bahattin Berkan Betin and Cafer Can Heptepe and Efe Batı Güleç and Yavuz Emre Yağcı and Aysel Kantürk Figen and Bilge Coşkuner Filiz}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85203289247&doi=10.1016%2fj.matlet.2024.137354&partnerID=40&md5=7acc0ce0e562efbfb255c06722aa49bc}, doi = {10.1016/j.matlet.2024.137354}, year = {2024}, date = {2024-01-01}, volume = {377}, abstract = {The effects of Expanded Natural Graphite (ENG) content, powder mixing method and compaction pressure on the tensile strengths of Magnesium AZ91 (9 wt% Al, 1 wt% Zn and 0.2 wt% Mn) + ENG powder mixture pellets were investigated. The tensile strengths of the pellets increased with an increase in the ENG content and compaction pressure and also with the applied powder ball milling. However, the compaction pressures above 500 MPa resulted in shear banding. © 2024}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effects of Expanded Natural Graphite (ENG) content, powder mixing method and compaction pressure on the tensile strengths of Magnesium AZ91 (9 wt% Al, 1 wt% Zn and 0.2 wt% Mn) + ENG powder mixture pellets were investigated. The tensile strengths of the pellets increased with an increase in the ENG content and compaction pressure and also with the applied powder ball milling. However, the compaction pressures above 500 MPa resulted in shear banding. © 2024 |
Movahedi, Nima; Fiedler, Thomas; Sarıkaya, Mustafa; Taşdemirci, Alper; Murch, Graeme E; Belova, Irina V; Güden, Mustafa Dynamic Compression of Metal Syntactic Foam-Filled Aluminum Tubes Journal Article 2024. @article{Movahedi2024b, title = {Dynamic Compression of Metal Syntactic Foam-Filled Aluminum Tubes}, author = {Nima Movahedi and Thomas Fiedler and Mustafa Sarıkaya and Alper Taşdemirci and Graeme E Murch and Irina V Belova and Mustafa Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85198745483&doi=10.1007%2fs11665-024-09825-5&partnerID=40&md5=4df9e4a30678b89ad11b1d1af85ba212}, doi = {10.1007/s11665-024-09825-5}, year = {2024}, date = {2024-01-01}, abstract = {The current research investigates the compressive properties of metal syntactic foam (MSF)-filled tubes at dynamic loads with an impact velocity of 4 m/s. For this purpose, A356 aluminum alloy syntactic foams were prepared using an infiltration casting technique with an incorporation of expanded perlite (EP) filler particles. The study involves the testing and comparison of both MSF samples and MSF-filled tubes under dynamic loading scenarios. In the case of MSF-filled tubes, aluminum tubes are either fully filled (FFT) or half-filled (HFT) with MSFs. The manufactured foams and foam cores have a similar macroscopic density across all tested samples. Under dynamic loading, the MSF, HFT, and FFT samples exhibit distinct and different deformation mechanisms. In MSFs, dynamic compression is controlled by shearing of the sample, whereas in HFTs and FFTs, dynamic deformation occurs through the folding and buckling of the tubes, accompanied by partial deformation of the MSF cores. © ASM International 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The current research investigates the compressive properties of metal syntactic foam (MSF)-filled tubes at dynamic loads with an impact velocity of 4 m/s. For this purpose, A356 aluminum alloy syntactic foams were prepared using an infiltration casting technique with an incorporation of expanded perlite (EP) filler particles. The study involves the testing and comparison of both MSF samples and MSF-filled tubes under dynamic loading scenarios. In the case of MSF-filled tubes, aluminum tubes are either fully filled (FFT) or half-filled (HFT) with MSFs. The manufactured foams and foam cores have a similar macroscopic density across all tested samples. Under dynamic loading, the MSF, HFT, and FFT samples exhibit distinct and different deformation mechanisms. In MSFs, dynamic compression is controlled by shearing of the sample, whereas in HFTs and FFTs, dynamic deformation occurs through the folding and buckling of the tubes, accompanied by partial deformation of the MSF cores. © ASM International 2024. |
2023 |
Enser, Samed; Guden, Mustafa; Tasdemirci, Alper; Davut, Kemal The strain rate history effect in a selective-laser-melt 316L stainless steel Journal Article MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 862 , 2023. @article{WOS:000905147200003, title = {The strain rate history effect in a selective-laser-melt 316L stainless steel}, author = {Samed Enser and Mustafa Guden and Alper Tasdemirci and Kemal Davut}, doi = {10.1016/j.msea.2022.144439}, year = {2023}, date = {2023-01-01}, journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, volume = {862}, abstract = {The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. |
Tuncer, C; Güden, M; Orhan, M; Sarıkaya, M K; Taşdemirci, A Quasi-static and dynamic Brazilian testing and failure analysis of a deer antler in the transverse to the osteon growth direction Journal Article Journal of the Mechanical Behavior of Biomedical Materials, 138 , 2023. @article{Tuncer2023, title = {Quasi-static and dynamic Brazilian testing and failure analysis of a deer antler in the transverse to the osteon growth direction}, author = {C Tuncer and M Güden and M Orhan and M K Sarıkaya and A Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85145658319&doi=10.1016%2fj.jmbbm.2023.105648&partnerID=40&md5=f2b3c0121aa41d2857249a24554f05da}, doi = {10.1016/j.jmbbm.2023.105648}, year = {2023}, date = {2023-01-01}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {138}, abstract = {The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5–44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5–44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces. © 2023 Elsevier Ltd |
Enser, S; Güden, M; Taşdemirci, A; Davut, K The strain rate history effect in a selective-laser-melt 316L stainless steel Journal Article Materials Science and Engineering A, 862 , 2023. @article{Enser2023, title = {The strain rate history effect in a selective-laser-melt 316L stainless steel}, author = {S Enser and M Güden and A Taşdemirci and K Davut}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85143677799&doi=10.1016%2fj.msea.2022.144439&partnerID=40&md5=d3e4693f86b0e95c1ee6eb89a46551aa}, doi = {10.1016/j.msea.2022.144439}, year = {2023}, date = {2023-01-01}, journal = {Materials Science and Engineering A}, volume = {862}, abstract = {The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi-static (10−3 s−1) and high strain rate (1600-3200 s−1) interrupted and reloading compression tests. The specimens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was ∼70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in ∼60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher fraction of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi-static (10−3 s−1) and high strain rate (1600-3200 s−1) interrupted and reloading compression tests. The specimens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was ∼70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in ∼60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher fraction of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. © 2022 Elsevier B.V. |
Zeybek, M K; Güden, M; Taşdemirci, A Journal of Materials Engineering and Performance, 2023. @article{Zeybek2023, title = {The Effect of Strain Rate on the Compression Behavior of Additively Manufactured Short Carbon Fiber-Reinforced Polyamide Composites with Different Layer Heights, Infill Patterns, and Built Angles}, author = {M K Zeybek and M Güden and A Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85147762551&doi=10.1007%2fs11665-023-07918-1&partnerID=40&md5=e7bbc8949f442fcf22b8812d43a6fa1e}, doi = {10.1007/s11665-023-07918-1}, year = {2023}, date = {2023-01-01}, journal = {Journal of Materials Engineering and Performance}, abstract = {Previous studies on the fused deposition modelling (FDM) processed short carbon fiber/Polyamide 6 (PA6) matrix composites and neat PA6 have mostly concentrated on the quasi-static mechanical properties. Present study focused on the strain rate-dependent deformation behavior of a short carbon fiber-reinforced PA6 (Onyx) and neat PA6, produced in different layer heights, infill patterns and built angles. As compared with PA6, Onyx showed a higher compression stress at all strain rates investigated. A layer height of 0.2 mm in PA6 specimens promoted a better bonding between [0/90°] infill layers; hence, a higher flow stress than 0.2 mm layer height specimens, while 0.2 mm layer height induced a higher porosity in Onyx specimens, leading to a lower flow stress. The porosities in Onyx [0/90°] infill specimens were due to the constraining effect of 0/90° fiber layers. Changing infill pattern from a [0/90°] to a concentric one decreased porosity at the same layer height and hence increased the compressive flow stress. The highest compressive strength was found in the specimens with the loading axis 90 and 0° to [0/90°] infill plane. The lowest strength was, however, determined in the specimens with the loading axis 30 and 60o to [0/90°] infill plane in quasi-static loading. However, the specimens with the loading axis of 60, 45, 30 and 0° exhibited a brittle behavior in high strain rate loading (1500 s−1). The specimens with the loading axis of 45° had the lowest fracture stress and strain in the high strain rate loading. This signified the importance of loading angle at high strain rates. Finally, the rate sensitivities of PA6 and Onyx specimens were shown to be similar, showing a matrix dominated deformation. However, the strain rate jump tests indicated a slightly higher rate sensitivity of Onyx specimens at quasi-static strain rates (10−3-10−1 s−1). © 2023, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Previous studies on the fused deposition modelling (FDM) processed short carbon fiber/Polyamide 6 (PA6) matrix composites and neat PA6 have mostly concentrated on the quasi-static mechanical properties. Present study focused on the strain rate-dependent deformation behavior of a short carbon fiber-reinforced PA6 (Onyx) and neat PA6, produced in different layer heights, infill patterns and built angles. As compared with PA6, Onyx showed a higher compression stress at all strain rates investigated. A layer height of 0.2 mm in PA6 specimens promoted a better bonding between [0/90°] infill layers; hence, a higher flow stress than 0.2 mm layer height specimens, while 0.2 mm layer height induced a higher porosity in Onyx specimens, leading to a lower flow stress. The porosities in Onyx [0/90°] infill specimens were due to the constraining effect of 0/90° fiber layers. Changing infill pattern from a [0/90°] to a concentric one decreased porosity at the same layer height and hence increased the compressive flow stress. The highest compressive strength was found in the specimens with the loading axis 90 and 0° to [0/90°] infill plane. The lowest strength was, however, determined in the specimens with the loading axis 30 and 60o to [0/90°] infill plane in quasi-static loading. However, the specimens with the loading axis of 60, 45, 30 and 0° exhibited a brittle behavior in high strain rate loading (1500 s−1). The specimens with the loading axis of 45° had the lowest fracture stress and strain in the high strain rate loading. This signified the importance of loading angle at high strain rates. Finally, the rate sensitivities of PA6 and Onyx specimens were shown to be similar, showing a matrix dominated deformation. However, the strain rate jump tests indicated a slightly higher rate sensitivity of Onyx specimens at quasi-static strain rates (10−3-10−1 s−1). © 2023, ASM International. |
Turan, A K; Tasdemirci, A; Kara, A; Sahin, S; Guden, M Thin-Walled Structures, 182 , 2023. @article{Turan2023, title = {Investigation of penetration behavior of combined geometry shells at quasi-static and intermediate strain rates: An experimental and numerical study}, author = {A K Turan and A Tasdemirci and A Kara and S Sahin and M Guden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85140804922&doi=10.1016%2fj.tws.2022.110261&partnerID=40&md5=a68187ac67baf30b83898f98789e157e}, doi = {10.1016/j.tws.2022.110261}, year = {2023}, date = {2023-01-01}, journal = {Thin-Walled Structures}, volume = {182}, abstract = {In this study, the penetration/perforation behavior of a core material with previously determined static and dynamic crushing characteristics was investigated both experimentally and numerically. Penetration/perforation problems occur due to shrapnel effect when sandwich structures containing energy-absorbing core materials by crushing are exposed to blast loads. The penetration behavior of combined geometry shells consisting of a hemispherical cap and a cylindrical segment was investigated experimentally using blunt, conical and hemispherical penetrator tips. The quasi-static penetration tests were performed in a universal test machine, and the intermediate strain rate penetration tests were performed in a drop weight test device. The numerical models of penetration tests were implemented in LS-DYNA at the test strain rates as well as at the higher strain rates. Results showed that different penetrator geometries induced damage forms of symmetrical tearing, petaling, plugging and inversely formed hemispherical domed cone. The increase in the thickness of core geometry resulted in a decent increase in force–displacement curves, as average of force levels increased around 140%, 200% and 220% for blunt, conical and hemispherical tip penetrators, respectively. Numerical results indicated very good correlation with experimental work and enabled to investigate effect of strain rate and micro-inertia over numerical models at elevated penetrator velocities. Penetration behavior was found to be affected from micro-inertia effects up to a threshold displacement of 4 mm for thicker and 5 mm for thinner core units and strain rate effects were found to be dominant beyond that point. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the penetration/perforation behavior of a core material with previously determined static and dynamic crushing characteristics was investigated both experimentally and numerically. Penetration/perforation problems occur due to shrapnel effect when sandwich structures containing energy-absorbing core materials by crushing are exposed to blast loads. The penetration behavior of combined geometry shells consisting of a hemispherical cap and a cylindrical segment was investigated experimentally using blunt, conical and hemispherical penetrator tips. The quasi-static penetration tests were performed in a universal test machine, and the intermediate strain rate penetration tests were performed in a drop weight test device. The numerical models of penetration tests were implemented in LS-DYNA at the test strain rates as well as at the higher strain rates. Results showed that different penetrator geometries induced damage forms of symmetrical tearing, petaling, plugging and inversely formed hemispherical domed cone. The increase in the thickness of core geometry resulted in a decent increase in force–displacement curves, as average of force levels increased around 140%, 200% and 220% for blunt, conical and hemispherical tip penetrators, respectively. Numerical results indicated very good correlation with experimental work and enabled to investigate effect of strain rate and micro-inertia over numerical models at elevated penetrator velocities. Penetration behavior was found to be affected from micro-inertia effects up to a threshold displacement of 4 mm for thicker and 5 mm for thinner core units and strain rate effects were found to be dominant beyond that point. © 2022 Elsevier Ltd |
Güden, Mustafa; Ülker, Sevkan; Movahedi, Nima Epoxy matrix nano composites: modulus, strength and ductility enhancement through auxeticity of α-Cristobalite filler Journal Article Materials Letters, 349 , 2023. @article{Güden2023, title = {Epoxy matrix nano composites: modulus, strength and ductility enhancement through auxeticity of α-Cristobalite filler}, author = {Mustafa Güden and Sevkan Ülker and Nima Movahedi}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162134261&doi=10.1016%2fj.matlet.2023.134759&partnerID=40&md5=34d79791a88c5b5655fa411fe0895b99}, doi = {10.1016/j.matlet.2023.134759}, year = {2023}, date = {2023-01-01}, journal = {Materials Letters}, volume = {349}, abstract = {The negative Poisson's ratio (NPR) nano-size α-Cristobalite particle/epoxy composites were prepared and tensile tested. The elastic modulus and strength of the composites were improved as the particle volume fraction increased from 0 to 0.02. Unlike the conventional particle reinforced composites, the fracture strain increased with the nano α-Cristobalite addition, an effect which was ascribed to the intrinsic NPR behavior of the filler. © 2023 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The negative Poisson's ratio (NPR) nano-size α-Cristobalite particle/epoxy composites were prepared and tensile tested. The elastic modulus and strength of the composites were improved as the particle volume fraction increased from 0 to 0.02. Unlike the conventional particle reinforced composites, the fracture strain increased with the nano α-Cristobalite addition, an effect which was ascribed to the intrinsic NPR behavior of the filler. © 2023 Elsevier B.V. |
Güden, Mustafa; Riaz, Arslan Bin; Toksoy, Ahmet Kaan; Yıldıztekin, Murat; Erten, Hacer İrem; Çimen, Gülden; Hızlı, Burak; Çellek, Burçin Seven; Güleç, Efe; Taşdemirci, Alper; Yavaş, Hakan; Altınok, Sertaç Materials Science and Engineering: A, 885 , 2023. @article{Güden2023b, title = {Investigation and validation of the flow stress equation and damage model parameters of an electron beam melted Ti6Al4V alloy with a martensitic phase}, author = {Mustafa Güden and Arslan Bin Riaz and Ahmet Kaan Toksoy and Murat Yıldıztekin and Hacer İrem Erten and Gülden Çimen and Burak Hızlı and Burçin Seven Çellek and Efe Güleç and Alper Taşdemirci and Hakan Yavaş and Sertaç Altınok}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171624739&doi=10.1016%2fj.msea.2023.145590&partnerID=40&md5=206e908384653029d335d5611a983306}, doi = {10.1016/j.msea.2023.145590}, year = {2023}, date = {2023-01-01}, journal = {Materials Science and Engineering: A}, volume = {885}, abstract = {The Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of α' (martensite) and α+β and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of α′ phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post-peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain. © 2023 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of α' (martensite) and α+β and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of α′ phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post-peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain. © 2023 Elsevier B.V. |
Çelik, Muhammet; Güden, Mustafa; Sarıkaya, Mustafa; Taşdemirci, Alper; Genç, Cem; Ersoy, Kurtuluş; Serin, Özgür Composite Structures, 320 , 2023. @article{Çelik2023, title = {The impact response of a Nomex® honeycomb core/E-glass/epoxy composite sandwich structure to increasing velocities: Experimental and numerical analysis}, author = {Muhammet Çelik and Mustafa Güden and Mustafa Sarıkaya and Alper Taşdemirci and Cem Genç and Kurtuluş Ersoy and Özgür Serin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162005169&doi=10.1016%2fj.compstruct.2023.117205&partnerID=40&md5=fb47471b22e7653bc2d670c7a45b347b}, doi = {10.1016/j.compstruct.2023.117205}, year = {2023}, date = {2023-01-01}, journal = {Composite Structures}, volume = {320}, abstract = {The impact response of an E-glass fiber reinforced epoxy/Nomex® honeycomb core sandwich was investigated both experimentally and numerically at increasing velocities through concentrated quasi-static indentation force (CQIF), low velocity impact (LVI) and high velocity impact (HVI) tests. The composite face sheets and core were modelled using MAT_162 and MAT_026 homogenized material model in LS-DYNA, respectively. The experimental and numerical LVI test forces corresponding to core crushing and face sheet penetration were shown to be higher than those of the CQIF tests and increased as the impactor velocity increased. The increase of the impact forces at increasing velocities was largely ascribed to the inertia and the strain rate sensitive fracture strength of the composite sheets. The core shearing was detected in the CQIF and LVI tests both experimentally and numerically. It was also detected in the HVI tests at the velocities less than 20 m s−1. The deformation in the HVI tests at and above ∼ 29.4 m s−1 was highly localized in the impact area with no core shearing and a large delamination damage area at the front face sheet. The force enhancement due to the micro-inertia of the core deformation was shown to be not significant at the studied velocities. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The impact response of an E-glass fiber reinforced epoxy/Nomex® honeycomb core sandwich was investigated both experimentally and numerically at increasing velocities through concentrated quasi-static indentation force (CQIF), low velocity impact (LVI) and high velocity impact (HVI) tests. The composite face sheets and core were modelled using MAT_162 and MAT_026 homogenized material model in LS-DYNA, respectively. The experimental and numerical LVI test forces corresponding to core crushing and face sheet penetration were shown to be higher than those of the CQIF tests and increased as the impactor velocity increased. The increase of the impact forces at increasing velocities was largely ascribed to the inertia and the strain rate sensitive fracture strength of the composite sheets. The core shearing was detected in the CQIF and LVI tests both experimentally and numerically. It was also detected in the HVI tests at the velocities less than 20 m s−1. The deformation in the HVI tests at and above ∼ 29.4 m s−1 was highly localized in the impact area with no core shearing and a large delamination damage area at the front face sheet. The force enhancement due to the micro-inertia of the core deformation was shown to be not significant at the studied velocities. © 2023 Elsevier Ltd |
Sarıkaya, Mustafa; Güden, Mustafa; Kambur, Çağdaş; Özbek, Sevim Çankaya; Taşdemirci, Alper Development of the Johnson-Cook flow stress and damage parameters for the impact response of polycarbonate: Experimental and numerical approach Journal Article International Journal of Impact Engineering, 179 , 2023. @article{Sarıkaya2023, title = {Development of the Johnson-Cook flow stress and damage parameters for the impact response of polycarbonate: Experimental and numerical approach}, author = {Mustafa Sarıkaya and Mustafa Güden and Çağdaş Kambur and Sevim Çankaya Özbek and Alper Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85160689008&doi=10.1016%2fj.ijimpeng.2023.104674&partnerID=40&md5=26109d206458c5db0dfc878ae314e9b4}, doi = {10.1016/j.ijimpeng.2023.104674}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Impact Engineering}, volume = {179}, abstract = {The Johnson and Cook (JC) flow stress and damage model parameters of a polycarbonate (PC) plate were determined by the mechanical tests and numerical simulations of the tests. The experimental tests included quasi-static and high strain rate tension and compression, quasi-static notched-specimen tension, quasi-static indentation (QSI), low velocity impact (LVI) and projectile impact (PI). Initially, five different quasi-static flow stress-strain equations were extracted from the experimental and numerical tests. The flow stress equation determined from the experimental average true stress-true strain curve well agreed with the effective stress-strain obtained from the quasi-static numerical tension test. The numerical QSI force-displacement curve based on the experimental average true stress-true strain equation was further shown to be very similar to that of the experiment. The LVI and PI test simulations were then continued with the experimental average true stress-true strain equation using five different flow stress-strain rate relations: JC, Huh and Kang (HK), Allen-Rule and Jones (ARJ), Cowper-Symonds (CS) and the nonlinear rate approach (NLA). The rate sensitivity parameters of these relations were extracted from the quasi-static and high strain rate tests. The LVI test simulations using the stress-strain rate relations exhibited force-displacement curves higher than those of the experiments. The detected almost no strain rate sensitivity in the LVI tests was ascribed to low strain rate dependency of the flow stress at these intermediate strain rates and large strains involved. On the other side, all the stress-strain rate relations investigated nearly predicted the experimental damage types: dishing at 100 and 140 m s−1 and petalling at 160 m s−1, except the CS relation which predicted the fracture of the plate at 140 m s−1. The experimental average projectile exit velocity at 160 m s−1 was further well predicted by the used stress-strain rate relations while the experimental average petal thicknesses were under estimated by the models. The absorbed energy at 160 m s−1 PI test was determined 1.6 times that of the QSI test, which proved an increased energy absorption capability of the tested PC at the investigated impact velocities. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Johnson and Cook (JC) flow stress and damage model parameters of a polycarbonate (PC) plate were determined by the mechanical tests and numerical simulations of the tests. The experimental tests included quasi-static and high strain rate tension and compression, quasi-static notched-specimen tension, quasi-static indentation (QSI), low velocity impact (LVI) and projectile impact (PI). Initially, five different quasi-static flow stress-strain equations were extracted from the experimental and numerical tests. The flow stress equation determined from the experimental average true stress-true strain curve well agreed with the effective stress-strain obtained from the quasi-static numerical tension test. The numerical QSI force-displacement curve based on the experimental average true stress-true strain equation was further shown to be very similar to that of the experiment. The LVI and PI test simulations were then continued with the experimental average true stress-true strain equation using five different flow stress-strain rate relations: JC, Huh and Kang (HK), Allen-Rule and Jones (ARJ), Cowper-Symonds (CS) and the nonlinear rate approach (NLA). The rate sensitivity parameters of these relations were extracted from the quasi-static and high strain rate tests. The LVI test simulations using the stress-strain rate relations exhibited force-displacement curves higher than those of the experiments. The detected almost no strain rate sensitivity in the LVI tests was ascribed to low strain rate dependency of the flow stress at these intermediate strain rates and large strains involved. On the other side, all the stress-strain rate relations investigated nearly predicted the experimental damage types: dishing at 100 and 140 m s−1 and petalling at 160 m s−1, except the CS relation which predicted the fracture of the plate at 140 m s−1. The experimental average projectile exit velocity at 160 m s−1 was further well predicted by the used stress-strain rate relations while the experimental average petal thicknesses were under estimated by the models. The absorbed energy at 160 m s−1 PI test was determined 1.6 times that of the QSI test, which proved an increased energy absorption capability of the tested PC at the investigated impact velocities. © 2023 Elsevier Ltd |
Mauko, Anja; Sarıkaya, Mustafa; Güden, Mustafa; Duarte, Isabel; Borovinšek, Matej; Vesenjak, Matej; Ren, Zoran High strain-rate deformation analysis of open-cell aluminium foam Journal Article Journal of Materials Research and Technology, 25 , pp. 1208 – 1221, 2023, (All Open Access, Gold Open Access, Green Open Access). @article{Mauko20231208, title = {High strain-rate deformation analysis of open-cell aluminium foam}, author = {Anja Mauko and Mustafa Sarıkaya and Mustafa Güden and Isabel Duarte and Matej Borovinšek and Matej Vesenjak and Zoran Ren}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162885101&doi=10.1016%2fj.jmrt.2023.05.280&partnerID=40&md5=a55525f2fe8789924a5b73ce11d13a7a}, doi = {10.1016/j.jmrt.2023.05.280}, year = {2023}, date = {2023-01-01}, journal = {Journal of Materials Research and Technology}, volume = {25}, pages = {1208 – 1221}, abstract = {This study investigated the high-strain rate mechanical properties of open-cell aluminium foam M-pore®. While previous research has examined the response of this type of foam under quasi-static and transitional dynamic loading conditions, there is a lack of knowledge about its behaviour under higher strain rates (transitional and shock loading regimes). To address this gap in understanding, cylindrical open-cell foam specimens were tested using a modified Direct Impact Hopkinson Bar (DIHB) apparatus over a wide range of strain rates, up to 93 m/s. The results showed a strong dependency of the foam's behaviour on the loading rate, with increased plateau stress and changes in deformation front formation and propagation at higher strain rates. The internal structure of the specimens was examined using X-ray micro-computed tomography (mCT). The mCT images were used to build simplified 3D numerical models of analysed aluminium foam specimens that were used in computational simulations of their behaviour under all experimentally tested loading regimes using LS-DYNA software. The overall agreement between the experimental and computational results was good enough to validate the built numerical models capable of correctly simulating the mechanical response of analysed aluminium foam at different loading rates. © 2023 The Authors}, note = {All Open Access, Gold Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study investigated the high-strain rate mechanical properties of open-cell aluminium foam M-pore®. While previous research has examined the response of this type of foam under quasi-static and transitional dynamic loading conditions, there is a lack of knowledge about its behaviour under higher strain rates (transitional and shock loading regimes). To address this gap in understanding, cylindrical open-cell foam specimens were tested using a modified Direct Impact Hopkinson Bar (DIHB) apparatus over a wide range of strain rates, up to 93 m/s. The results showed a strong dependency of the foam's behaviour on the loading rate, with increased plateau stress and changes in deformation front formation and propagation at higher strain rates. The internal structure of the specimens was examined using X-ray micro-computed tomography (mCT). The mCT images were used to build simplified 3D numerical models of analysed aluminium foam specimens that were used in computational simulations of their behaviour under all experimentally tested loading regimes using LS-DYNA software. The overall agreement between the experimental and computational results was good enough to validate the built numerical models capable of correctly simulating the mechanical response of analysed aluminium foam at different loading rates. © 2023 The Authors |
2022 |
Ulker, Sevkan; Guden, Mustafa MATERIALS EXPRESS, 12 (8), pp. 1094-1107, 2022. @article{WOS:000897716200001, title = {The effect of the temperature of heat treatment process and the concentration and duration of acid leaching on the size and crystallinity of nano-silica powders formed by the dissociation of natural diatom frustule}, author = {Sevkan Ulker and Mustafa Guden}, doi = {10.1166/mex.2022.2251}, year = {2022}, date = {2022-08-01}, journal = {MATERIALS EXPRESS}, volume = {12}, number = {8}, pages = {1094-1107}, abstract = {The present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling. |
Tuzgel, F; Akbulut, E F; Guzel, E; Yucesoy, A; Sahin, S; Tasdemirci, A; Guden, M Testing and modeling blast loading of a sandwich structure cored with a bio-inspired (balanus) core Journal Article Thin-Walled Structures, 175 , 2022. @article{Tuzgel2022, title = {Testing and modeling blast loading of a sandwich structure cored with a bio-inspired (balanus) core}, author = {F Tuzgel and E F Akbulut and E Guzel and A Yucesoy and S Sahin and A Tasdemirci and M Guden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85127099692&doi=10.1016%2fj.tws.2022.109185&partnerID=40&md5=598aa9ba4baa82852c1ddd0b8676727c}, doi = {10.1016/j.tws.2022.109185}, year = {2022}, date = {2022-01-01}, journal = {Thin-Walled Structures}, volume = {175}, abstract = {The blast loading response of a sandwich structure consisted of bio-inspired (balanus) cores/units was investigated experimentally and numerically. A Direct Pressure Pulse (DPP) set-up was used to impose a blast-like loading. The equivalent blast conditions corresponding to the used impact velocities were implemented in the models. A benchmark study was performed by using three different methods namely pure Lagrangian, Arbitrary Lagrangian Eulerian, and hybrid. Dynamic crushing behavior was analyzed and exhibited a higher specific energy absorption capacity than its constituents (core and shell). Among the core configurations, all-front configuration was found the most efficient configuration regarding the specific energy absorption. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The blast loading response of a sandwich structure consisted of bio-inspired (balanus) cores/units was investigated experimentally and numerically. A Direct Pressure Pulse (DPP) set-up was used to impose a blast-like loading. The equivalent blast conditions corresponding to the used impact velocities were implemented in the models. A benchmark study was performed by using three different methods namely pure Lagrangian, Arbitrary Lagrangian Eulerian, and hybrid. Dynamic crushing behavior was analyzed and exhibited a higher specific energy absorption capacity than its constituents (core and shell). Among the core configurations, all-front configuration was found the most efficient configuration regarding the specific energy absorption. © 2022 Elsevier Ltd |
Güden, M; Alpkaya, A T; Hamat, B A; Hızlı, B; Taşdemirci, A; Tanrıkulu, A A; Yavaş, H Strain, 58 (3), 2022. @article{Güden2022, title = {The quasi-static crush response of electron-beam-melt Ti6Al4V body-centred-cubic lattices: The effect of the number of cells, strut diameter and face sheet}, author = {M Güden and A T Alpkaya and B A Hamat and B Hızlı and A Taşdemirci and A A Tanrıkulu and H Yavaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125105289&doi=10.1111%2fstr.12411&partnerID=40&md5=e6515c23c4247096157d4bec2da4a9f3}, doi = {10.1111/str.12411}, year = {2022}, date = {2022-01-01}, journal = {Strain}, volume = {58}, number = {3}, abstract = {The effect of the number of cells, strut diameter and face sheet on the compression of electron-beam-melt (EBM) Ti6Al4V (Ti64) body-centred-cubic (BCC) lattices was investigated experimentally and numerically. The lattices with the same relative density (~0.182) were fabricated with and without 2-mm-thick face sheets in 10 and 5 mm cell size, 8–125 unit cell (two to five cells/edge) and 2 and 1 mm strut diameter. The experimental compression tests were further numerically simulated in the LS-DYNA. Experimentally two bending-dominated crushing modes, namely, lateral and diagonal layer crushing, were determined. The numerical models however exhibited merely a bending-dominated lateral layer crushing mode when the erosion strain was 0.4 and without face-sheet models showed a diagonal layer crushing mode when the erosion strain was 0.3. Lower erosion strains promoted a diagonal layer crushing mode by introducing geometrical inhomogeneity to the lattice, leading to strain localisation as similar to the face sheets which introduced extensive strut bending in the layers adjacent to the face sheets. The face-sheet model showed a higher but decreasing collapse strength at an increasing number of cells, just as opposite to the without face-sheet model, and the collapse strength of both models converged when the number of cells was higher than five-cell/edge. The decrease/increase of the collapse strengths of lattices before the critical number of cells was claimed mainly due to the size-imposed lattice boundary condition, rather than the specimen volume. The difference in the experimental collapse strengths between the 5- and the 10-mm cell-size lattices was ascribed to the variations in the microstructures—hence the material model parameters between the small-diameter and the large-diameter EBM-Ti64 strut lattices. © 2022 John Wiley & Sons Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of the number of cells, strut diameter and face sheet on the compression of electron-beam-melt (EBM) Ti6Al4V (Ti64) body-centred-cubic (BCC) lattices was investigated experimentally and numerically. The lattices with the same relative density (~0.182) were fabricated with and without 2-mm-thick face sheets in 10 and 5 mm cell size, 8–125 unit cell (two to five cells/edge) and 2 and 1 mm strut diameter. The experimental compression tests were further numerically simulated in the LS-DYNA. Experimentally two bending-dominated crushing modes, namely, lateral and diagonal layer crushing, were determined. The numerical models however exhibited merely a bending-dominated lateral layer crushing mode when the erosion strain was 0.4 and without face-sheet models showed a diagonal layer crushing mode when the erosion strain was 0.3. Lower erosion strains promoted a diagonal layer crushing mode by introducing geometrical inhomogeneity to the lattice, leading to strain localisation as similar to the face sheets which introduced extensive strut bending in the layers adjacent to the face sheets. The face-sheet model showed a higher but decreasing collapse strength at an increasing number of cells, just as opposite to the without face-sheet model, and the collapse strength of both models converged when the number of cells was higher than five-cell/edge. The decrease/increase of the collapse strengths of lattices before the critical number of cells was claimed mainly due to the size-imposed lattice boundary condition, rather than the specimen volume. The difference in the experimental collapse strengths between the 5- and the 10-mm cell-size lattices was ascribed to the variations in the microstructures—hence the material model parameters between the small-diameter and the large-diameter EBM-Ti64 strut lattices. © 2022 John Wiley & Sons Ltd. |
Movahedi, N; Fiedler, T; Taşdemirci, A; Murch, G E; Belova, I V; Güden, M Impact loading of functionally graded metal syntactic foams Journal Article Materials Science and Engineering A, 839 , 2022. @article{Movahedi2022, title = {Impact loading of functionally graded metal syntactic foams}, author = {N Movahedi and T Fiedler and A Taşdemirci and G E Murch and I V Belova and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85124878036&doi=10.1016%2fj.msea.2022.142831&partnerID=40&md5=7c2f5ff50091f5c640df480605838c8c}, doi = {10.1016/j.msea.2022.142831}, year = {2022}, date = {2022-01-01}, journal = {Materials Science and Engineering A}, volume = {839}, abstract = {The present study addresses the impact loading of functionally graded metal syntactic foams (FG-MSF). For comparison, samples of the same material were also compression loaded at quasi-static velocities. Samples of A356 aluminium FG-MSF were produced using counter-gravity infiltration casting with combination of equal-sized layers of expanded perlite (EP) and activated carbon (AC) particles. A modified Split Hopkinson Pressure Bar test set-up was used to impact the FG-MSFs from their EP or AC layers at 55 m/s or 175 m/s impact velocities. A high-speed camera captured the deformation of the samples during testing. It was shown that increasing the loading velocity enhanced both the compressive proof strength and energy absorption of the impacted FG-MSF from both layers, confirming a dynamic strengthening effect of the foam. The samples impacted from both layers at 55 and 175 m/s showed a transition and a shock mode of deformation, respectively. The impacted samples at 55 m/s experienced lower final average strain values compared to 175 m/s. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study addresses the impact loading of functionally graded metal syntactic foams (FG-MSF). For comparison, samples of the same material were also compression loaded at quasi-static velocities. Samples of A356 aluminium FG-MSF were produced using counter-gravity infiltration casting with combination of equal-sized layers of expanded perlite (EP) and activated carbon (AC) particles. A modified Split Hopkinson Pressure Bar test set-up was used to impact the FG-MSFs from their EP or AC layers at 55 m/s or 175 m/s impact velocities. A high-speed camera captured the deformation of the samples during testing. It was shown that increasing the loading velocity enhanced both the compressive proof strength and energy absorption of the impacted FG-MSF from both layers, confirming a dynamic strengthening effect of the foam. The samples impacted from both layers at 55 and 175 m/s showed a transition and a shock mode of deformation, respectively. The impacted samples at 55 m/s experienced lower final average strain values compared to 175 m/s. © 2022 Elsevier B.V. |
Güden, M; Enser, S; Bayhan, M; Taşdemirci, A; Yavaş, H Materials Science and Engineering A, 838 , 2022. @article{Güden2022b, title = {The strain rate sensitive flow stresses and constitutive equations of a selective-laser-melt and an annealed-rolled 316L stainless steel: A comparative study}, author = {M Güden and S Enser and M Bayhan and A Taşdemirci and H Yavaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85124262590&doi=10.1016%2fj.msea.2022.142743&partnerID=40&md5=c9a9ea5a5d2240e3b1fb245fdb7f8e27}, doi = {10.1016/j.msea.2022.142743}, year = {2022}, date = {2022-01-01}, journal = {Materials Science and Engineering A}, volume = {838}, abstract = {The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys. © 2022 Elsevier B.V. |
2021 |
Aydin, Murat; Bulut, Tugrul; Guden, Mustafa; Erel, Nuri Transdiscal screw fixation in L5-S1 spondylolysis: A biomechanical study Transdiscal screw fixation in L5-51 spondylolysis Journal Article ANNALS OF CLINICAL AND ANALYTICAL MEDICINE, 12 (9), pp. 1055-1057, 2021. @article{WOS:000732457800019, title = {Transdiscal screw fixation in L5-S1 spondylolysis: A biomechanical study Transdiscal screw fixation in L5-51 spondylolysis}, author = {Murat Aydin and Tugrul Bulut and Mustafa Guden and Nuri Erel}, doi = {10.4328/ACAM.20586}, year = {2021}, date = {2021-09-01}, journal = {ANNALS OF CLINICAL AND ANALYTICAL MEDICINE}, volume = {12}, number = {9}, pages = {1055-1057}, abstract = {Aim: This study aimed to investigate whether the L5-S1 transdiscal screw fixation is biomechanically sufficient against axial loads and the resulting shear forces. Material and Methods: Eighteen fresh calf spines under 1 year of age were used in this study. Two randomly selected spines were used as test materials. The inferior facet and ligamentum flavum were removed in 7 randomly selected spines. In these spines (transdiscal screw group), two transdiscal screws were placed bilaterally between 15 and S1. Tests were performed on the remaining 9 spines, while the spines were initially intact (intact group) and after creating a listhesis model (injury group). The extent of displacement occurring as a result of axial loading was noted in all groups in order to calculate the load-displacement curves. Results: The mean displacement as a result of successive axial loadings of 5000 N was as follows: 3 mm (range: 2.4 - 4 mm) in the intact group, 3.5 mm (range: 3 - 4.5 mm) in the transdiscal screw group and 4.5 mm (range: 3.9 - 5 mm) In the group with injury. The difference was statistically significant (p<0.05). None of the samples exhibited broken screws, screw deformation or dislocation, even in failure tests, in the transdiscal screw group. Discussion: These findings have shown that transdiscal screw fixation can be biomechanically sufficient against the shear forces occurring as a result of axial loading. We believe that this technique can be a good alternative as a fixation method for the L5-S1 spondylolisthesis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Aim: This study aimed to investigate whether the L5-S1 transdiscal screw fixation is biomechanically sufficient against axial loads and the resulting shear forces. Material and Methods: Eighteen fresh calf spines under 1 year of age were used in this study. Two randomly selected spines were used as test materials. The inferior facet and ligamentum flavum were removed in 7 randomly selected spines. In these spines (transdiscal screw group), two transdiscal screws were placed bilaterally between 15 and S1. Tests were performed on the remaining 9 spines, while the spines were initially intact (intact group) and after creating a listhesis model (injury group). The extent of displacement occurring as a result of axial loading was noted in all groups in order to calculate the load-displacement curves. Results: The mean displacement as a result of successive axial loadings of 5000 N was as follows: 3 mm (range: 2.4 - 4 mm) in the intact group, 3.5 mm (range: 3 - 4.5 mm) in the transdiscal screw group and 4.5 mm (range: 3.9 - 5 mm) In the group with injury. The difference was statistically significant (p<0.05). None of the samples exhibited broken screws, screw deformation or dislocation, even in failure tests, in the transdiscal screw group. Discussion: These findings have shown that transdiscal screw fixation can be biomechanically sufficient against the shear forces occurring as a result of axial loading. We believe that this technique can be a good alternative as a fixation method for the L5-S1 spondylolisthesis. |
Enser, S; Yavas, H; Hamat, B A; Aydın, H; Kafadar, G; Tanrıkulu, A A; Kazdal, H Z; Ozturk, F; Güden, M Comparing Compression Deformation and Rate Sensitivity of Additively Manufactured and Extruded-Annealed 316L Alloys Journal Article Journal of Materials Engineering and Performance, 30 (12), pp. 8831-8840, 2021. @article{Enser20218831, title = {Comparing Compression Deformation and Rate Sensitivity of Additively Manufactured and Extruded-Annealed 316L Alloys}, author = {S Enser and H Yavas and B A Hamat and H Aydın and G Kafadar and A A Tanrıkulu and H Z Kazdal and F Ozturk and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85118462128&doi=10.1007%2fs11665-021-06340-9&partnerID=40&md5=d25a9a6e9c2f3be728f463e1a9b2e3a0}, doi = {10.1007/s11665-021-06340-9}, year = {2021}, date = {2021-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {30}, number = {12}, pages = {8831-8840}, abstract = {The deformation behavior of a selective-laser-melt-processed 316-L alloy (SLM-316L) under compression was determined together with a commercial annealed-extruded 316L alloy bar (C-316L) for comparison. Strain rate jump tests and hardness tests on the untested and compression tested samples were also performed. Extensive microscopic observations on the deformed and undeformed samples showed a twinning-dominated deformation in SLM-316L, similar to twinning-induced-plasticity steels, while a martensitic transformation-dominated deformation in C-316L alloy, similar to transformation-induced-plasticity steels. Within the studied quasi-static strain rate regime, the measured higher strain rate sensitivity of SLM-316L was ascribed to the lower distances between the nano-twins, in the level of 100 nm, than the distances between martensite plates, in the level of 1000 nm. A higher hardness increase in the martensite transformation region as compared with the twinned region proved the higher work hardening of C-316L. The hardness tests in the micron and sub-micron levels further confirmed the previously determined relatively low resistances of the dislocation cell walls (sub-grain) to the dislocation motion in SLM-316L alloy. © 2021, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The deformation behavior of a selective-laser-melt-processed 316-L alloy (SLM-316L) under compression was determined together with a commercial annealed-extruded 316L alloy bar (C-316L) for comparison. Strain rate jump tests and hardness tests on the untested and compression tested samples were also performed. Extensive microscopic observations on the deformed and undeformed samples showed a twinning-dominated deformation in SLM-316L, similar to twinning-induced-plasticity steels, while a martensitic transformation-dominated deformation in C-316L alloy, similar to transformation-induced-plasticity steels. Within the studied quasi-static strain rate regime, the measured higher strain rate sensitivity of SLM-316L was ascribed to the lower distances between the nano-twins, in the level of 100 nm, than the distances between martensite plates, in the level of 1000 nm. A higher hardness increase in the martensite transformation region as compared with the twinned region proved the higher work hardening of C-316L. The hardness tests in the micron and sub-micron levels further confirmed the previously determined relatively low resistances of the dislocation cell walls (sub-grain) to the dislocation motion in SLM-316L alloy. © 2021, ASM International. |
Polat, D; Güden, M Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders Journal Article Construction and Building Materials, 300 , 2021. @article{Polat2021, title = {Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders}, author = {D Polat and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85110473118&doi=10.1016%2fj.conbuildmat.2021.124259&partnerID=40&md5=0d7a948bc247b782e77d4b5908d062f3}, doi = {10.1016/j.conbuildmat.2021.124259}, year = {2021}, date = {2021-01-01}, journal = {Construction and Building Materials}, volume = {300}, abstract = {Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C. © 2021 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C. © 2021 Elsevier Ltd |
Shi, C; Guo, B; Sarıkaya, M; Çelik, M; Chen, P; Güden, M International Journal of Impact Engineering, 149 , 2021. @article{Shi2021, title = {Determination of the material model and damage parameters of a carbon fiber reinforced laminated epoxy composite for high strain rate planar compression}, author = {C Shi and B Guo and M Sarıkaya and M Çelik and P Chen and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097220985&doi=10.1016%2fj.ijimpeng.2020.103771&partnerID=40&md5=eecdd1023b76f40453f6cd5e379c9ec8}, doi = {10.1016/j.ijimpeng.2020.103771}, year = {2021}, date = {2021-01-01}, journal = {International Journal of Impact Engineering}, volume = {149}, abstract = {The progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020}, keywords = {}, pubstate = {published}, tppubtype = {article} } The progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020 |
Güden, M; Canbaz, İ International Journal of Crashworthiness, 26 (1), pp. 38-52, 2021. @article{Güden202138, title = {The effect of cell wall material strain and strain-rate hardening behaviour on the dynamic crush response of an aluminium multi-layered corrugated core}, author = {M Güden and İ Canbaz}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074867388&doi=10.1080%2f13588265.2019.1682351&partnerID=40&md5=4c12613ac0ed4e34ef1ed09c892300c6}, doi = {10.1080/13588265.2019.1682351}, year = {2021}, date = {2021-01-01}, journal = {International Journal of Crashworthiness}, volume = {26}, number = {1}, pages = {38-52}, abstract = {The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s−1) and dynamic (20, 60, 150 and 250 m s−1) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s−1, transition mode at 60 m s−1 and quasi-static homogenous mode at 20 m s−1. The increase of velocity from quasi-static to 20 m s−1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s−1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s−1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys. © 2019 Informa UK Limited, trading as Taylor & Francis Group.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s−1) and dynamic (20, 60, 150 and 250 m s−1) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s−1, transition mode at 60 m s−1 and quasi-static homogenous mode at 20 m s−1. The increase of velocity from quasi-static to 20 m s−1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s−1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s−1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys. © 2019 Informa UK Limited, trading as Taylor & Francis Group. |
Güden, M; Yavaş, H; Tanrıkulu, A A; Taşdemirci, A; Akın, B; Enser, S; Karakuş, A; Hamat, B A Orientation dependent tensile properties of a selective-laser-melt 316L stainless steel Journal Article Materials Science and Engineering A, 824 , 2021. @article{Güden2021b, title = {Orientation dependent tensile properties of a selective-laser-melt 316L stainless steel}, author = {M Güden and H Yavaş and A A Tanrıkulu and A Taşdemirci and B Akın and S Enser and A Karakuş and B A Hamat}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85111194339&doi=10.1016%2fj.msea.2021.141808&partnerID=40&md5=d838bade5a0604998ddd4cb8ecce7457}, doi = {10.1016/j.msea.2021.141808}, year = {2021}, date = {2021-01-01}, journal = {Materials Science and Engineering A}, volume = {824}, abstract = {The effect of specimen inclination angle with respect to building direction on the tensile properties of a selective laser melt 316L alloy was investigated. Tensile test specimens were fabricated with the angles between 0° to 90° at 15° intervals using a rotation scanning. In addition, 316L alloy test specimens were generated in the ANSYS 2020R1 additive module and tensile tested in LS-DYNA in order to determine the effect of residual stresses on the tensile strengths. The microscopic analysis revealed a strong ⟨110⟩ fiber texture orientation along the building direction (the loading axis of 0° inclined specimens) and a weak <111> texture or nearly random distribution of directions in the normal to the building direction (tensile loading axis of 90° inclined specimens). The yield and tensile strength increased and ductility decreased with increasing inclination angle. The strength variation with the inclination angle was shown well-fitted with the Tsai-Hill failure criterion. Although, the used numerical models indicated an inclination-dependent residual stress, the difference in the residual stresses was much lower than the difference in the strengths between 0° and 90° inclined specimens. Predictions showed a lower twinning stress in 0° inclined specimens due to ⟨110⟩ fiber texture orientation in the tensile axis. The fiber texture resulted in extensive twinning; hence, higher ductility and tension-compression asymmetry in 0° inclined specimens. Based on these results, the variations in the strength and ductility of tested SLM-316L specimens with the inclination angle was ascribed to the variations in the angle between the fiber texture orientation and loading axis. © 2021 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of specimen inclination angle with respect to building direction on the tensile properties of a selective laser melt 316L alloy was investigated. Tensile test specimens were fabricated with the angles between 0° to 90° at 15° intervals using a rotation scanning. In addition, 316L alloy test specimens were generated in the ANSYS 2020R1 additive module and tensile tested in LS-DYNA in order to determine the effect of residual stresses on the tensile strengths. The microscopic analysis revealed a strong ⟨110⟩ fiber texture orientation along the building direction (the loading axis of 0° inclined specimens) and a weak <111> texture or nearly random distribution of directions in the normal to the building direction (tensile loading axis of 90° inclined specimens). The yield and tensile strength increased and ductility decreased with increasing inclination angle. The strength variation with the inclination angle was shown well-fitted with the Tsai-Hill failure criterion. Although, the used numerical models indicated an inclination-dependent residual stress, the difference in the residual stresses was much lower than the difference in the strengths between 0° and 90° inclined specimens. Predictions showed a lower twinning stress in 0° inclined specimens due to ⟨110⟩ fiber texture orientation in the tensile axis. The fiber texture resulted in extensive twinning; hence, higher ductility and tension-compression asymmetry in 0° inclined specimens. Based on these results, the variations in the strength and ductility of tested SLM-316L specimens with the inclination angle was ascribed to the variations in the angle between the fiber texture orientation and loading axis. © 2021 Elsevier B.V. |
Seven, S B; Çankaya, M A; Uysal, Ç; Tasdemirci, A; Saatçi, S; Güden, M Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete Journal Article Strain, 57 (2), 2021. @article{Seven2021, title = {Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete}, author = {S B Seven and M A Çankaya and Ç Uysal and A Tasdemirci and S Saatçi and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099175099&doi=10.1111%2fstr.12377&partnerID=40&md5=4651c623ee9ea5323e2e6b03771b2c5f}, doi = {10.1111/str.12377}, year = {2021}, date = {2021-01-01}, journal = {Strain}, volume = {57}, number = {2}, abstract = {The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. © 2021 John Wiley & Sons Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. © 2021 John Wiley & Sons Ltd |
2020 |
Zeren, Dogus; Senturk, Ufuk; Guden, Mustafa The expansion behavior of slurries containing recycled glass powder carboxymethyl cellulose, lime and aluminum powder Journal Article CONSTRUCTION AND BUILDING MATERIALS, 240 , 2020, ISSN: 0950-0618. @article{ISI:000527362400021, title = {The expansion behavior of slurries containing recycled glass powder carboxymethyl cellulose, lime and aluminum powder}, author = {Dogus Zeren and Ufuk Senturk and Mustafa Guden}, doi = {10.1016/j.conbuildmat.2019.117898}, issn = {0950-0618}, year = {2020}, date = {2020-04-01}, journal = {CONSTRUCTION AND BUILDING MATERIALS}, volume = {240}, abstract = {The rheology and foaming/expansion of the slurries of a waste/recycled glass powder with 50, 55 and 60 wt% of solid (glass powder) were experimentally investigated. The glass powder slurries were foamed using aluminum powder as foaming agent (0.75 wt%) and calcium hydroxide as activator (1 wt%). Sodium carboxymethyl cellulose (CMC) was added to the slurries as a binder with the amounts between 0 and 4 wt%. The expansions of the slurries were measured in-situ using a laser sensor and reported as percent volume expansion. The CMC-addition increased the viscosities of the slurries, particularly the fine size powder slurries. The slurries with the relatively low-viscosity exhibited lower initial expansion rates compared to the slurries with the relatively high-viscosity. The maximum expansions of the slurries increased from 300 to 350%, when the viscosity increased to 5 Pa s and reached a steady value around 400% between 5 and 50 Pa s. The expansions of the slurries could not be achieved above 50 Pa s since they became too thick to be foamed. The foam samples made from the slurries with 55 and 60 wt% of solid and sintered at 700 and 750 degrees C for 30 min had the average densities between 355 and 530 kg m(-3) and the average compressive strengths between 0.2 and 0.5 MPa. Increasing sintering time to 60 min at 750 degrees C increased the average compressive strength from 0.5 to 1.5 MPa for the foam samples made from the slurry with 60 wt% of solid. These proved that both sintering temperature and time were effective in increasing the compressive strengths of the foamed structures. The thermal conductivities of the sintered foam samples with the densities of 355 and 504 kg m(-3) were measured 0.042 and 0.057 W m(-1) K-1, respectively. (C) 2019 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The rheology and foaming/expansion of the slurries of a waste/recycled glass powder with 50, 55 and 60 wt% of solid (glass powder) were experimentally investigated. The glass powder slurries were foamed using aluminum powder as foaming agent (0.75 wt%) and calcium hydroxide as activator (1 wt%). Sodium carboxymethyl cellulose (CMC) was added to the slurries as a binder with the amounts between 0 and 4 wt%. The expansions of the slurries were measured in-situ using a laser sensor and reported as percent volume expansion. The CMC-addition increased the viscosities of the slurries, particularly the fine size powder slurries. The slurries with the relatively low-viscosity exhibited lower initial expansion rates compared to the slurries with the relatively high-viscosity. The maximum expansions of the slurries increased from 300 to 350%, when the viscosity increased to 5 Pa s and reached a steady value around 400% between 5 and 50 Pa s. The expansions of the slurries could not be achieved above 50 Pa s since they became too thick to be foamed. The foam samples made from the slurries with 55 and 60 wt% of solid and sintered at 700 and 750 degrees C for 30 min had the average densities between 355 and 530 kg m(-3) and the average compressive strengths between 0.2 and 0.5 MPa. Increasing sintering time to 60 min at 750 degrees C increased the average compressive strength from 0.5 to 1.5 MPa for the foam samples made from the slurry with 60 wt% of solid. These proved that both sintering temperature and time were effective in increasing the compressive strengths of the foamed structures. The thermal conductivities of the sintered foam samples with the densities of 355 and 504 kg m(-3) were measured 0.042 and 0.057 W m(-1) K-1, respectively. (C) 2019 Elsevier Ltd. All rights reserved. |
Kilicaslan, Cenk; Guden, Mustafa The effect of core height on energy absorbing capacity in aluminum corrugated sandwich panels Journal Article JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, 35 (1), pp. 17-26, 2020, ISSN: 1300-1884. @article{ISI:000520598100002, title = {The effect of core height on energy absorbing capacity in aluminum corrugated sandwich panels}, author = {Cenk Kilicaslan and Mustafa Guden}, doi = {10.17341/gazimmfd.639834}, issn = {1300-1884}, year = {2020}, date = {2020-01-01}, journal = {JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY}, volume = {35}, number = {1}, pages = {17-26}, abstract = {In this study, energy absorbing capacity of brazed and polyurethane adhesively bonded corrugated aluminum sandwich panels were investigated. In sandwich panels, Al 1050 H14 trapezoidal zig-zag corrugated cores and face and interlayer sheets were used. Each sandwich panel has core orientation of 0 degrees/0 degrees or 0 degrees/90 degrees. The cores used in these panels were smaller, core height is about 3 mm, in contrast to conventional sandwich cores. Impact tests were conducted at 3 and 6 m/s with spherical projectors. Adhesively bonded sandwich panels were also tested at 6 m/s with flat and conical projectors. Numerical models were prepared in LSDYNA to investigated the deformation behavior of cores. Panels tested with flat and conical projectors experienced complete perforation and absorbed more energy at configuration of 0 degrees/0 degrees core orientation. However, panels tested with spherical projectors were not perforated and they absorbed more energy at configuration of 0 degrees/90 degrees core orientation. Energy absorbing capacity of the panels were also compared to the panels having 9 mm height corrugated cores. The results showed that effective collapsing length was seen to increase due to increase in core height and impact energy distributed the whole panel surface more homogenous manner.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, energy absorbing capacity of brazed and polyurethane adhesively bonded corrugated aluminum sandwich panels were investigated. In sandwich panels, Al 1050 H14 trapezoidal zig-zag corrugated cores and face and interlayer sheets were used. Each sandwich panel has core orientation of 0 degrees/0 degrees or 0 degrees/90 degrees. The cores used in these panels were smaller, core height is about 3 mm, in contrast to conventional sandwich cores. Impact tests were conducted at 3 and 6 m/s with spherical projectors. Adhesively bonded sandwich panels were also tested at 6 m/s with flat and conical projectors. Numerical models were prepared in LSDYNA to investigated the deformation behavior of cores. Panels tested with flat and conical projectors experienced complete perforation and absorbed more energy at configuration of 0 degrees/0 degrees core orientation. However, panels tested with spherical projectors were not perforated and they absorbed more energy at configuration of 0 degrees/90 degrees core orientation. Energy absorbing capacity of the panels were also compared to the panels having 9 mm height corrugated cores. The results showed that effective collapsing length was seen to increase due to increase in core height and impact energy distributed the whole panel surface more homogenous manner. |
Seven, Semih Berk; Cankaya, Alper M; Uysal, Cetin; Tasdemirci, Alper; Saatci, Selcuk; Guden, Mustafa Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete Journal Article STRAIN, 2020, ISSN: 0039-2103. @article{ISI:000605351700001, title = {Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete}, author = {Semih Berk Seven and Alper M Cankaya and Cetin Uysal and Alper Tasdemirci and Selcuk Saatci and Mustafa Guden}, doi = {10.1111/str.12377, Early Access Date = JAN 2021}, issn = {0039-2103}, year = {2020}, date = {2020-00-00}, journal = {STRAIN}, abstract = {The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. |
2017 |
Odac, Ismet Kutlay; Guden, Mustafa; Klcaslan, Cenk; Tasdemirci, Alper The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 103 , pp. 64-75, 2017, ISSN: 0734-743X. @article{ISI:000395844400006, title = {The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling}, author = {Ismet Kutlay Odac and Mustafa Guden and Cenk Klcaslan and Alper Tasdemirci}, doi = {10.1016/j.ijimpeng.2016.10.014}, issn = {0734-743X}, year = {2017}, date = {2017-05-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {103}, pages = {64-75}, abstract = {An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved. |
Zeren, Dogus; Guden, Mustafa The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules Journal Article JOURNAL OF COMPOSITE MATERIALS, 51 (12), pp. 1681-1691, 2017, ISSN: 0021-9983. @article{ISI:000401035100002, title = {The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules}, author = {Dogus Zeren and Mustafa Guden}, doi = {10.1177/0021998316669855}, issn = {0021-9983}, year = {2017}, date = {2017-05-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {51}, number = {12}, pages = {1681-1691}, abstract = {Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200 degrees C for 2h and used as filler/reinforcing agent (15wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900 degrees C The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7x10(-3)s(-1). The results showed that the inclusion of the frustules heat-treated at 1000 degrees C increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000 degrees C and the as-received frustules increased the strength by similar to 25% and 16%, respectively. The heat treatment above 1000 degrees C decreased the surface area of the frustules from 8.23m(2)g(-1) to 3.46m(2)g(-1). The cristobalite grains of the frustules heat-treated at 1000 degrees C was smaller than 100nm, while the grain size increased to similar to 500nm at 1200 degrees C. The increased compressive stresses of the resin at the specific heat treatment temperature (1000 degrees C) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000 degrees C were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200 degrees C for 2h and used as filler/reinforcing agent (15wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900 degrees C The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7x10(-3)s(-1). The results showed that the inclusion of the frustules heat-treated at 1000 degrees C increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000 degrees C and the as-received frustules increased the strength by similar to 25% and 16%, respectively. The heat treatment above 1000 degrees C decreased the surface area of the frustules from 8.23m(2)g(-1) to 3.46m(2)g(-1). The cristobalite grains of the frustules heat-treated at 1000 degrees C was smaller than 100nm, while the grain size increased to similar to 500nm at 1200 degrees C. The increased compressive stresses of the resin at the specific heat treatment temperature (1000 degrees C) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000 degrees C were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion. |
2016 |
Turkan, Ugur; Guden, Mustafa; Sudagidan, Mert Staphylococcus epidermidis adhesion on surface-treated open-cell Ti6Al4V foams Journal Article BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK, 61 (3), pp. 299-307, 2016, ISSN: 0013-5585. @article{ISI:000377547000006, title = {Staphylococcus epidermidis adhesion on surface-treated open-cell Ti6Al4V foams}, author = {Ugur Turkan and Mustafa Guden and Mert Sudagidan}, doi = {10.1515/bmt-2015-0007}, issn = {0013-5585}, year = {2016}, date = {2016-06-01}, journal = {BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK}, volume = {61}, number = {3}, pages = {299-307}, abstract = {The effect of alkali and nitric acid surface treatments on the adhesion of Staphylococcus epidermidis to the surface of 60% porous open-cell Ti6Al4V foam was investigated. The resultant surface roughness of foam particles was determined from the ground flat surfaces of thin foam specimens. Alkali treatment formed a porous, rough Na2Ti5O11 surface layer on Ti6Al4V particles, while nitric acid treatment increased the number of undulations on foam flat and particle surfaces, leading to the development of finer surface topographical features. Both surface treatments increased the nanometric-scale surface roughness of particles and the number of bacteria adhering to the surface, while the adhesion was found to be significantly higher in alkali-treated foam sample. The significant increase in the number of bacterial attachment on the alkali-treated sample was attributed to the formation of a highly porous and nanorough Na2Ti5O11 surface layer.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of alkali and nitric acid surface treatments on the adhesion of Staphylococcus epidermidis to the surface of 60% porous open-cell Ti6Al4V foam was investigated. The resultant surface roughness of foam particles was determined from the ground flat surfaces of thin foam specimens. Alkali treatment formed a porous, rough Na2Ti5O11 surface layer on Ti6Al4V particles, while nitric acid treatment increased the number of undulations on foam flat and particle surfaces, leading to the development of finer surface topographical features. Both surface treatments increased the nanometric-scale surface roughness of particles and the number of bacteria adhering to the surface, while the adhesion was found to be significantly higher in alkali-treated foam sample. The significant increase in the number of bacterial attachment on the alkali-treated sample was attributed to the formation of a highly porous and nanorough Na2Ti5O11 surface layer. |
Tasdemirci, Alper; Kara, Ali; Turan, Kivanc; Sahin, Selim; Guden, Mustafa Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures Journal Article THIN-WALLED STRUCTURES, 100 , pp. 180-191, 2016, ISSN: 0263-8231. @article{ISI:000369463600016, title = {Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures}, author = {Alper Tasdemirci and Ali Kara and Kivanc Turan and Selim Sahin and Mustafa Guden}, doi = {10.1016/j.tws.2015.12.012}, issn = {0263-8231}, year = {2016}, date = {2016-03-01}, journal = {THIN-WALLED STRUCTURES}, volume = {100}, pages = {180-191}, abstract = {The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved. |
2014 |
Demir, Mustafa M; Horzum, Nesrin; Tasdemirci, Alper; Turan, Kivanc; Guden, Mustafa Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix Journal Article ACS APPLIED MATERIALS & INTERFACES, 6 (24), pp. 21901-21905, 2014, ISSN: 1944-8244. @article{ISI:000347139400018, title = {Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix}, author = {Mustafa M Demir and Nesrin Horzum and Alper Tasdemirci and Kivanc Turan and Mustafa Guden}, doi = {10.1021/am507029c}, issn = {1944-8244}, year = {2014}, date = {2014-12-01}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {6}, number = {24}, pages = {21901-21905}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kilicaslan, C; Odaci, I K; Tasdemirci, A; Guden, M STRAIN, 50 (3), pp. 236-249, 2014, ISSN: 1475-1305. @article{ISI:000336487800004, title = {Experimental Testing and Full and Homogenized Numerical Models of the Low Velocity and Dynamic Deformation of the Trapezoidal Aluminium Corrugated Core Sandwich}, author = {C Kilicaslan and I K Odaci and A Tasdemirci and M Guden}, doi = {10.1111/str.12085}, issn = {1475-1305}, year = {2014}, date = {2014-06-01}, journal = {STRAIN}, volume = {50}, number = {3}, pages = {236-249}, abstract = {The simulations of the low velocity and dynamic deformation of a multi-layer 1050-H14 Al trapezoidal zig-zag corrugated core sandwich were investigated using the homogenized models (solid models) of a single core layer (without face sheets). In the first part of the study, the LS-DYNA MAT-26 material model parameters of a single core layer were developed through experimental and numerical compression tests on the single core layer. In the second part, the fidelities of the developed numerical models were checked by the split-Hopkinson pressure bar direct impact, low velocity compression and indentation and projectile impact tests. The results indicated that the element size had a significant effect on the initial peak and post-peak stresses of the homogenized models of the direct impact testing of the single-layer corrugated sandwich. This was attributed to the lack of the inertial effects in the homogenized models, which resulted in reduced initial peak stresses as compared with the full model and experiment. However, the homogenized models based on the experimental stress-strain curve of the single core layer predicted the low velocity compression and indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy and reduced the computational time of the models significantly.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The simulations of the low velocity and dynamic deformation of a multi-layer 1050-H14 Al trapezoidal zig-zag corrugated core sandwich were investigated using the homogenized models (solid models) of a single core layer (without face sheets). In the first part of the study, the LS-DYNA MAT-26 material model parameters of a single core layer were developed through experimental and numerical compression tests on the single core layer. In the second part, the fidelities of the developed numerical models were checked by the split-Hopkinson pressure bar direct impact, low velocity compression and indentation and projectile impact tests. The results indicated that the element size had a significant effect on the initial peak and post-peak stresses of the homogenized models of the direct impact testing of the single-layer corrugated sandwich. This was attributed to the lack of the inertial effects in the homogenized models, which resulted in reduced initial peak stresses as compared with the full model and experiment. However, the homogenized models based on the experimental stress-strain curve of the single core layer predicted the low velocity compression and indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy and reduced the computational time of the models significantly. |
Ozyildiz, Figen; Uzel, Atac; Hazar, Ayse Serpil; Guden, Mustafa; Olmez, Sultan; Aras, Isil; Karaboz, Ismail Photocatalytic antimicrobial effect of TiO2 anatase thin-film-coated orthodontic arch wires on 3 oral pathogens Journal Article TURKISH JOURNAL OF BIOLOGY, 38 (2), pp. 289-295, 2014, ISSN: 1300-0152. @article{ISI:000332944300015, title = {Photocatalytic antimicrobial effect of TiO2 anatase thin-film-coated orthodontic arch wires on 3 oral pathogens}, author = {Figen Ozyildiz and Atac Uzel and Ayse Serpil Hazar and Mustafa Guden and Sultan Olmez and Isil Aras and Ismail Karaboz}, doi = {10.3906/biy-1308-43}, issn = {1300-0152}, year = {2014}, date = {2014-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {38}, number = {2}, pages = {289-295}, abstract = {The aim of this study was to introduce antimicrobial activity to stainless steel orthodontic arch wires by coating them with TiO2 in anatase form. Stainless steel (0.016 x 0.022 inch), D-rect (0.016 x 0.022 inch), and multistranded hammered retainer wires (0.014 x 0.018 inch) were coated with TiO2 anatase by the sol-gel dip coating method. The wires were assessed for their photocatalytic antimicrobial activity against Streptococcus mutans, Candida albicans, and Enterococcus faecalis. After illumination under UVA (315400 nm) at 1.0 mW/cm(2) for 1 h, the reduction efficiencies of the anatase-coated arch wires were calculated by using colony-forming unit counts. All anatase-coated arch wires showed remarkable inhibitor effects against the test microorganisms under UVA. The most efficient wire on S. mutans was the stainless steel wire, with a 99.99% reduction in growth, but multistranded hammered retainer wire was the most active against both C. albicans and E. faecalis, with 98.0% and 91.68% reduction rates, respectively. TiO2-coated arch wires exposed to UVA illumination showed significant antimicrobial activity when compared with uncoated samples and coated, but not UVA-exposed, samples. Our results suggest that the antimicrobial effect of TiO2-coated arch wires in long-lasting orthodontic treatments would be beneficial for the prophylaxis of caries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this study was to introduce antimicrobial activity to stainless steel orthodontic arch wires by coating them with TiO2 in anatase form. Stainless steel (0.016 x 0.022 inch), D-rect (0.016 x 0.022 inch), and multistranded hammered retainer wires (0.014 x 0.018 inch) were coated with TiO2 anatase by the sol-gel dip coating method. The wires were assessed for their photocatalytic antimicrobial activity against Streptococcus mutans, Candida albicans, and Enterococcus faecalis. After illumination under UVA (315400 nm) at 1.0 mW/cm(2) for 1 h, the reduction efficiencies of the anatase-coated arch wires were calculated by using colony-forming unit counts. All anatase-coated arch wires showed remarkable inhibitor effects against the test microorganisms under UVA. The most efficient wire on S. mutans was the stainless steel wire, with a 99.99% reduction in growth, but multistranded hammered retainer wire was the most active against both C. albicans and E. faecalis, with 98.0% and 91.68% reduction rates, respectively. TiO2-coated arch wires exposed to UVA illumination showed significant antimicrobial activity when compared with uncoated samples and coated, but not UVA-exposed, samples. Our results suggest that the antimicrobial effect of TiO2-coated arch wires in long-lasting orthodontic treatments would be beneficial for the prophylaxis of caries. |
2013 |
Attila, Yigit; Guden, Mustafa; Tasdemirci, Alper Foam glass processing using a polishing glass powder residue Journal Article CERAMICS INTERNATIONAL, 39 (5), pp. 5869-5877, 2013, ISSN: 0272-8842. @article{ISI:000318577600141, title = {Foam glass processing using a polishing glass powder residue}, author = {Yigit Attila and Mustafa Guden and Alper Tasdemirci}, doi = {10.1016/j.ceramint.2012.12.104}, issn = {0272-8842}, year = {2013}, date = {2013-07-01}, journal = {CERAMICS INTERNATIONAL}, volume = {39}, number = {5}, pages = {5869-5877}, abstract = {The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Cakircali, Metin; Kilicaslan, Cenk; Guden, Mustafa; Kiranli, Engin; Shchukin, Valery Y; Petronko, Vladimir V Cross wedge rolling of a Ti6Al4V (ELI) alloy: the experimental studies and the finite element simulation of the deformation and failure Journal Article INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, 65 (9-12), pp. 1273-1287, 2013, ISSN: 0268-3768. @article{ISI:000316364000007, title = {Cross wedge rolling of a Ti6Al4V (ELI) alloy: the experimental studies and the finite element simulation of the deformation and failure}, author = {Metin Cakircali and Cenk Kilicaslan and Mustafa Guden and Engin Kiranli and Valery Y Shchukin and Vladimir V Petronko}, doi = {10.1007/s00170-012-4256-3}, issn = {0268-3768}, year = {2013}, date = {2013-04-01}, journal = {INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY}, volume = {65}, number = {9-12}, pages = {1273-1287}, abstract = {The cross wedge rolling (CWR) deformation and fracture of a Ti6Al4Al (ELI) alloy were investigated experimentally and numerically using a coupled thermo-mechanical finite element model analysis. The experimentally determined flow stress and damage model parameters were verified by tension split Hopkinson pressure bar testing of notched samples. The simulation and experimental CWR forces showed well agreements except near the end of the stretching zone. The model analysis showed that the temperature distribution in the work piece was non-uniform during the CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. The cracks were shown numerically to initiate in the midsections of the work piece during the guiding action and elongated in a direction normal to the maximum tensile stress triaxiality, resulting in cruciform-shaped crack formation, which was well agreed with the previously observed crack shape.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The cross wedge rolling (CWR) deformation and fracture of a Ti6Al4Al (ELI) alloy were investigated experimentally and numerically using a coupled thermo-mechanical finite element model analysis. The experimentally determined flow stress and damage model parameters were verified by tension split Hopkinson pressure bar testing of notched samples. The simulation and experimental CWR forces showed well agreements except near the end of the stretching zone. The model analysis showed that the temperature distribution in the work piece was non-uniform during the CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. The cracks were shown numerically to initiate in the midsections of the work piece during the guiding action and elongated in a direction normal to the maximum tensile stress triaxiality, resulting in cruciform-shaped crack formation, which was well agreed with the previously observed crack shape. |
Kesici, Kutsal; Tuney, Inci; Zeren, Dogus; Guden, Mustafa; Sukatar, Atakan Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea Journal Article TURKISH JOURNAL OF BIOLOGY, 37 (5), pp. 530-537, 2013, ISSN: 1300-0152. @article{ISI:000325300500004, title = {Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea}, author = {Kutsal Kesici and Inci Tuney and Dogus Zeren and Mustafa Guden and Atakan Sukatar}, doi = {10.3906/biy-1205-40}, issn = {1300-0152}, year = {2013}, date = {2013-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {37}, number = {5}, pages = {530-537}, abstract = {Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms. |
Gulturk, E A; Guden, M; Tasdemirci, A Calcined and natural frustules filled epoxy matrices: The effect of volume fraction on the tensile and compression behavior Journal Article COMPOSITES PART B-ENGINEERING, 44 (1), pp. 491-500, 2013, ISSN: 1359-8368. @article{ISI:000313854200059, title = {Calcined and natural frustules filled epoxy matrices: The effect of volume fraction on the tensile and compression behavior}, author = {E A Gulturk and M Guden and A Tasdemirci}, doi = {10.1016/j.compositesb.2012.03.022}, issn = {1359-8368}, year = {2013}, date = {2013-01-01}, journal = {COMPOSITES PART B-ENGINEERING}, volume = {44}, number = {1}, pages = {491-500}, abstract = {The effects of calcined diatom (CD) and natural diatom (ND) frustules filling (0-12 vol.%) on the quasi-static tensile and quasi-static and high strain rate compression behavior of an epoxy matrix were investigated experimentally. The high strain rate testing of frustules-filled and neat epoxy samples was performed in a compression Split Hopkinson Pressure Bar set-up. The frustules filling increased the stress values at a constant strain and decreased the tensile failure strains of the epoxy matrix. Compression tests results showed that frustules filling of epoxy increased both elastic modulus and yield strength values at quasi-static and high strain rates. While, a higher strengthening effect and strain rate sensitivity were found with ND frustules filling. Microscopic observations revealed two main compression deformation modes at quasi-static strain rates: the debonding of the frustules from the epoxy and/or crushing of the frustules. However, the failure of the filled composites at high strain rates was dominated by the fracture of epoxy matrix. (C) 2012 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effects of calcined diatom (CD) and natural diatom (ND) frustules filling (0-12 vol.%) on the quasi-static tensile and quasi-static and high strain rate compression behavior of an epoxy matrix were investigated experimentally. The high strain rate testing of frustules-filled and neat epoxy samples was performed in a compression Split Hopkinson Pressure Bar set-up. The frustules filling increased the stress values at a constant strain and decreased the tensile failure strains of the epoxy matrix. Compression tests results showed that frustules filling of epoxy increased both elastic modulus and yield strength values at quasi-static and high strain rates. While, a higher strengthening effect and strain rate sensitivity were found with ND frustules filling. Microscopic observations revealed two main compression deformation modes at quasi-static strain rates: the debonding of the frustules from the epoxy and/or crushing of the frustules. However, the failure of the filled composites at high strain rates was dominated by the fracture of epoxy matrix. (C) 2012 Elsevier Ltd. All rights reserved. |
2012 |
Tasdemirci, A; Turan, A K; Guden, M The effect of strain rate on the mechanical behavior of Teflon foam Journal Article POLYMER TESTING, 31 (6), pp. 723-727, 2012, ISSN: 0142-9418. @article{ISI:000307614000002, title = {The effect of strain rate on the mechanical behavior of Teflon foam}, author = {A Tasdemirci and A K Turan and M Guden}, doi = {10.1016/j.polymertesting.2012.05.004}, issn = {0142-9418}, year = {2012}, date = {2012-09-01}, journal = {POLYMER TESTING}, volume = {31}, number = {6}, pages = {723-727}, abstract = {The quasi-static (1 x 10(-3), 1 x 10(-2) and 1 x 10(-1) s(-1)) and high strain rate (7200 and 9500 s(-1)) experimental and high strain rate numerical compression deformation of a Gore Polarchip (TM) CP7003 heat insulating Teflon foam was investigated. High strain rate tests were conducted with the insertion of quartz crystal piezoelectric transducers at the end of the transmitter bar of a compression Split Hopkinson Pressure Bar (SHPB) set-up in order to measure the force at the back face of the specimen. A fully developed numerical model of the SHPB test on Teflon was also implemented using LS-DYNA. The simulation stresses showed close correlations with the experimentally measured stresses on the bars. The developed model successfully simulated the high strain rate loading. The damage initiation and progression of experimental high strain rate tests were further recorded using a high speed camera and found to be very similar to those of the simulation high strain rate tests. (C) 2012 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quasi-static (1 x 10(-3), 1 x 10(-2) and 1 x 10(-1) s(-1)) and high strain rate (7200 and 9500 s(-1)) experimental and high strain rate numerical compression deformation of a Gore Polarchip (TM) CP7003 heat insulating Teflon foam was investigated. High strain rate tests were conducted with the insertion of quartz crystal piezoelectric transducers at the end of the transmitter bar of a compression Split Hopkinson Pressure Bar (SHPB) set-up in order to measure the force at the back face of the specimen. A fully developed numerical model of the SHPB test on Teflon was also implemented using LS-DYNA. The simulation stresses showed close correlations with the experimentally measured stresses on the bars. The developed model successfully simulated the high strain rate loading. The damage initiation and progression of experimental high strain rate tests were further recorded using a high speed camera and found to be very similar to those of the simulation high strain rate tests. (C) 2012 Elsevier Ltd. All rights reserved. |
Savaci, Umut; Yilmaz, Sinan; Guden, Mustafa Open cell lead foams: processing, microstructure, and mechanical properties Journal Article JOURNAL OF MATERIALS SCIENCE, 47 (15), pp. 5646-5654, 2012, ISSN: 0022-2461. @article{ISI:000304110400004, title = {Open cell lead foams: processing, microstructure, and mechanical properties}, author = {Umut Savaci and Sinan Yilmaz and Mustafa Guden}, doi = {10.1007/s10853-012-6496-x}, issn = {0022-2461}, year = {2012}, date = {2012-08-01}, journal = {JOURNAL OF MATERIALS SCIENCE}, volume = {47}, number = {15}, pages = {5646-5654}, abstract = {Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations. |
Tasdemirci, A; Tunusoglu, G; Guden, M The effect of the interlayer on the ballistic performance of ceramic/composite armors: Experimental and numerical study Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 44 , pp. 1-9, 2012, ISSN: 0734-743X. @article{ISI:000301473600001, title = {The effect of the interlayer on the ballistic performance of ceramic/composite armors: Experimental and numerical study}, author = {A Tasdemirci and G Tunusoglu and M Guden}, doi = {10.1016/j.ijimpeng.2011.12.005}, issn = {0734-743X}, year = {2012}, date = {2012-06-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {44}, pages = {1-9}, abstract = {The effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration. (C) 2011 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration. (C) 2011 Elsevier Ltd. All rights reserved. |
Odaci, Ismet Kutlay; Kilicaslan, Cenk; Tasdemirci, Alper; Guden, Mustafa INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 17 (5), pp. 508-518, 2012, ISSN: 1358-8265. @article{ISI:000308991800004, title = {Projectile impact testing of glass fiber-reinforced composite and layered corrugated aluminium and aluminium foam core sandwich panels: a comparative study}, author = {Ismet Kutlay Odaci and Cenk Kilicaslan and Alper Tasdemirci and Mustafa Guden}, doi = {10.1080/13588265.2012.690215}, issn = {1358-8265}, year = {2012}, date = {2012-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {17}, number = {5}, pages = {508-518}, abstract = {E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate.}, keywords = {}, pubstate = {published}, tppubtype = {article} } E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate. |
2011 |
Turkan, Ugur; Guden, Mustafa The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution (vol 39, pg 1805, 2010) Journal Article CERAMICS INTERNATIONAL, 37 (2), pp. 693, 2011, ISSN: 0272-8842. @article{ISI:000286957900040, title = {The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution (vol 39, pg 1805, 2010)}, author = {Ugur Turkan and Mustafa Guden}, doi = {10.1016/j.ceramint.2010.07.002}, issn = {0272-8842}, year = {2011}, date = {2011-03-01}, journal = {CERAMICS INTERNATIONAL}, volume = {37}, number = {2}, pages = {693}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Durmus, A; Guden, M; Gulcimen, B; Ulku, S; Musa, E Experimental investigations on the ballistic impact performances of cold rolled sheet metals Journal Article MATERIALS & DESIGN, 32 (3), pp. 1356-1366, 2011, ISSN: 0261-3069. @article{ISI:000286904200033, title = {Experimental investigations on the ballistic impact performances of cold rolled sheet metals}, author = {A Durmus and M Guden and B Gulcimen and S Ulku and E Musa}, doi = {10.1016/j.matdes.2010.09.016}, issn = {0261-3069}, year = {2011}, date = {2011-03-01}, journal = {MATERIALS & DESIGN}, volume = {32}, number = {3}, pages = {1356-1366}, abstract = {This study focuses on the ballistic performances of 1 and 2 mm-thick and 2 x 1 mm-thick cold rolled sheet metal plates against 9 mm standard NATO projectile. The velocity of the projectile before and after perforation, the diameter of the front face deformation, the depth of the crater and the diameter of the hole were measured. The fracture surfaces of the plates near the ballistic limit were also microscopically analyzed. The highest ballistic limit was found in 2 mm-thick plate (332 m s(-1)) and the lowest in 1 mm-thick plate (97 m s(-1)). While, the ballistic limit of 2 x 1 mm-thick plate decreased to 306 m s(-1). Typical failure mechanism of the projectile was the flattening and mushrooming at relatively low velocities and the separation from the jacket at relatively high velocities. In accord with the ballistic limits, 2 mm-thick target plate exhibited the highest hardness value. Microscopic investigations showed the significant reductions in the grain size of the targets after the test. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study focuses on the ballistic performances of 1 and 2 mm-thick and 2 x 1 mm-thick cold rolled sheet metal plates against 9 mm standard NATO projectile. The velocity of the projectile before and after perforation, the diameter of the front face deformation, the depth of the crater and the diameter of the hole were measured. The fracture surfaces of the plates near the ballistic limit were also microscopically analyzed. The highest ballistic limit was found in 2 mm-thick plate (332 m s(-1)) and the lowest in 1 mm-thick plate (97 m s(-1)). While, the ballistic limit of 2 x 1 mm-thick plate decreased to 306 m s(-1). Typical failure mechanism of the projectile was the flattening and mushrooming at relatively low velocities and the separation from the jacket at relatively high velocities. In accord with the ballistic limits, 2 mm-thick target plate exhibited the highest hardness value. Microscopic investigations showed the significant reductions in the grain size of the targets after the test. (C) 2010 Elsevier Ltd. All rights reserved. |
Toksoy, A K; Guden, M The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes Journal Article INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 16 (1), pp. 97-109, 2011, ISSN: 1358-8265. @article{ISI:000288960900009, title = {The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes}, author = {A K Toksoy and M Guden}, doi = {10.1080/13588265.2010.514774}, issn = {1358-8265}, year = {2011}, date = {2011-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {16}, number = {1}, pages = {97-109}, abstract = {Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%-40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%-40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements. |
2010 |
Turkan, U; Guden, M The effect of nitric acid surface treatment on CaP deposition of Ti6Al4V open-cell foams in SBF solution Journal Article SURFACE & COATINGS TECHNOLOGY, 205 (7), pp. 1904-1916, 2010, ISSN: 0257-8972. @article{ISI:000286343100017, title = {The effect of nitric acid surface treatment on CaP deposition of Ti6Al4V open-cell foams in SBF solution}, author = {U Turkan and M Guden}, doi = {10.1016/j.surfcoat.2010.08.071}, issn = {0257-8972}, year = {2010}, date = {2010-12-01}, journal = {SURFACE & COATINGS TECHNOLOGY}, volume = {205}, number = {7}, pages = {1904-1916}, abstract = {The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 m in pore size), prepared by means of the space holder method using 94 and 66 mu m average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens. (C) 2010 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 m in pore size), prepared by means of the space holder method using 94 and 66 mu m average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens. (C) 2010 Elsevier B.V. All rights reserved. |
Turkan, Ugur; Guden, Mustafa The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution Journal Article CERAMICS INTERNATIONAL, 36 (6), pp. 1805-1816, 2010, ISSN: 0272-8842. @article{ISI:000280027800008, title = {The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution}, author = {Ugur Turkan and Mustafa Guden}, doi = {10.1016/j.ceramint.2010.03.030}, issn = {0272-8842}, year = {2010}, date = {2010-08-01}, journal = {CERAMICS INTERNATIONAL}, volume = {36}, number = {6}, pages = {1805-1816}, abstract = {The effects of alkali and nitric acid surface treatment and acid etching on the CaP deposition of an open cell Ti6Al4V foam (60% porous and 300-500 mu m in pore size) developed for biomedical applications were investigated in a simulated body fluid (SBF) solution for 14-day. The surface roughness of the foam specimens ground flat surfaces was measured in nano-metric scale before and after SBF immersion using an atomic force microscope (AFM). A significant increase in the surface roughness of alkali treated foam specimen after SBF immersion indicated a smaller crystal size CaP deposition, which was also confirmed by the AFM micrographs. The microscopic evaluation clearly showed that alkali treatment and nitric acid treatment induced a continuous, uniform CaP deposition on the cell wall surfaces of the foam (interior of cells). While in untreated foam specimen the cells are filled with CaP precipitates and acid etching did not produce a continuous coating layer on particles interior of the cells. The coating layer thickness was similar to 3 mu m in alkali treated foam specimens after 14-day of SBF immersion, while nitric acid treatment induced relatively thinner coating layer, 0.6 mu m. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effects of alkali and nitric acid surface treatment and acid etching on the CaP deposition of an open cell Ti6Al4V foam (60% porous and 300-500 mu m in pore size) developed for biomedical applications were investigated in a simulated body fluid (SBF) solution for 14-day. The surface roughness of the foam specimens ground flat surfaces was measured in nano-metric scale before and after SBF immersion using an atomic force microscope (AFM). A significant increase in the surface roughness of alkali treated foam specimen after SBF immersion indicated a smaller crystal size CaP deposition, which was also confirmed by the AFM micrographs. The microscopic evaluation clearly showed that alkali treatment and nitric acid treatment induced a continuous, uniform CaP deposition on the cell wall surfaces of the foam (interior of cells). While in untreated foam specimen the cells are filled with CaP precipitates and acid etching did not produce a continuous coating layer on particles interior of the cells. The coating layer thickness was similar to 3 mu m in alkali treated foam specimens after 14-day of SBF immersion, while nitric acid treatment induced relatively thinner coating layer, 0.6 mu m. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Ozyildiz, E; Guden, M; Uzel, A; Karaboz, I; Akil, O; Bulut, H Antimicrobial Activity of TiO2-coated Orthodontic Ceramic Brackets against Streptococcus mutans and Candida albicans Journal Article BIOTECHNOLOGY AND BIOPROCESS ENGINEERING, 15 (4), pp. 680-685, 2010, ISSN: 1226-8372. @article{ISI:000281514400022, title = {Antimicrobial Activity of TiO2-coated Orthodontic Ceramic Brackets against Streptococcus mutans and Candida albicans}, author = {E Ozyildiz and M Guden and A Uzel and I Karaboz and O Akil and H Bulut}, doi = {10.1007/s12257-009-3005-4}, issn = {1226-8372}, year = {2010}, date = {2010-07-01}, journal = {BIOTECHNOLOGY AND BIOPROCESS ENGINEERING}, volume = {15}, number = {4}, pages = {680-685}, abstract = {Polycrystalline alumina ceramic orthodontic brackets were coated with anatase TiO2 film via a sol-gel dip-coating method. The surface structure morphology and composition of the films were evaluated via scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The antimicrobial activity of the ceramic brackets was assessed against two oral pathogens, S. mutans and C. albicans. The results demonstrated that TiO2-coated brackets exposed to low energy UV-A illumination efficiently reduced the populations of test microorganisms relative to the uncoated brackets. The reduction efficiencies were 98% for S. mutans ATCC 10449 and 93% for C. albicans ATCC 60193.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Polycrystalline alumina ceramic orthodontic brackets were coated with anatase TiO2 film via a sol-gel dip-coating method. The surface structure morphology and composition of the films were evaluated via scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The antimicrobial activity of the ceramic brackets was assessed against two oral pathogens, S. mutans and C. albicans. The results demonstrated that TiO2-coated brackets exposed to low energy UV-A illumination efficiently reduced the populations of test microorganisms relative to the uncoated brackets. The reduction efficiencies were 98% for S. mutans ATCC 10449 and 93% for C. albicans ATCC 60193. |
Toksoy, A K; Guden, M Partial Al foam filling of commercial 1050H14 Al crash boxes: The effect of box column thickness and foam relative density on energy absorption Journal Article THIN-WALLED STRUCTURES, 48 (7), pp. 482-494, 2010, ISSN: 0263-8231. @article{ISI:000278670400002, title = {Partial Al foam filling of commercial 1050H14 Al crash boxes: The effect of box column thickness and foam relative density on energy absorption}, author = {A K Toksoy and M Guden}, doi = {10.1016/j.tws.2010.02.002}, issn = {0263-8231}, year = {2010}, date = {2010-07-01}, journal = {THIN-WALLED STRUCTURES}, volume = {48}, number = {7}, pages = {482-494}, abstract = {The crushing behavior of partially Al closed-cell foam filled commercial 1050H14 Al crash boxes was determined at quasi-static and dynamic deformation velocities. The quasi-static and dynamic crushing of the boxes were simulated using the LS-DYNA. The results showed that partial foam filling tended to change the deformation mode of empty boxes from a non-sequential to a sequential folding mode. In general, the experimental and simulation results showed similar mean load values and deformation modes. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling, however, decreases the critical foam filler density at increasing box wall thicknesses. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The crushing behavior of partially Al closed-cell foam filled commercial 1050H14 Al crash boxes was determined at quasi-static and dynamic deformation velocities. The quasi-static and dynamic crushing of the boxes were simulated using the LS-DYNA. The results showed that partial foam filling tended to change the deformation mode of empty boxes from a non-sequential to a sequential folding mode. In general, the experimental and simulation results showed similar mean load values and deformation modes. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling, however, decreases the critical foam filler density at increasing box wall thicknesses. (C) 2010 Elsevier Ltd. All rights reserved. |
Lecturer Dr. Özgür Günelsu
Educational Background
B.Sc. Middle East Technical University, Turkey, Mechanical Engineering, 2003
M.Sc. İstanbul Technical University, Turkey, Automotive Engineering, 2006
Ph.D. İstanbul Technical University, Turkey, Automotive Engineering, 2006
Research Interests
- Piston Secondary Dynamics and Lubrication
- +90 232 750 6762
- +90 232 750 6701
- Mechanical Engineering Building (101)
Publications
2014 |
Gunelsu, Ozgur; Akalin, Ozgen The Effects of Piston Skirt Profiles on Secondary Motion and Friction Journal Article JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, 136 (6), 2014, ISSN: 0742-4795. @article{ISI:000337939500013, title = {The Effects of Piston Skirt Profiles on Secondary Motion and Friction}, author = {Ozgur Gunelsu and Ozgen Akalin}, doi = {10.1115/1.4026486}, issn = {0742-4795}, year = {2014}, date = {2014-06-01}, journal = {JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME}, volume = {136}, number = {6}, abstract = {Piston skirt form deviating from a perfect cylinder is investigated numerically for an improved frictional performance. Three features defining the barrel and oval form of the skirt are compared in the search for lower friction power loss. Radius of curvature around the bulge of the barrel is changed to obtain a flatter or more-rounded lubricated area with respect to a hot-piston profile as well as the axial location of this bulge. On the other hand, the circumferential variation in the separation between the skirt and cylinder wall is represented by an elliptical piston and the aspect ratio is varied for comparison. These different skirt profiles are used in a developed piston secondary dynamics model solving for the lateral movement of the piston by calculating the hydrodynamic and boundary normal forces acting on the piston together with friction. Finally, an improved skirt profile is suggested to obtain better frictional efficiency.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Piston skirt form deviating from a perfect cylinder is investigated numerically for an improved frictional performance. Three features defining the barrel and oval form of the skirt are compared in the search for lower friction power loss. Radius of curvature around the bulge of the barrel is changed to obtain a flatter or more-rounded lubricated area with respect to a hot-piston profile as well as the axial location of this bulge. On the other hand, the circumferential variation in the separation between the skirt and cylinder wall is represented by an elliptical piston and the aspect ratio is varied for comparison. These different skirt profiles are used in a developed piston secondary dynamics model solving for the lateral movement of the piston by calculating the hydrodynamic and boundary normal forces acting on the piston together with friction. Finally, an improved skirt profile is suggested to obtain better frictional efficiency. |
Prof. Dr. Sinan Kandemir
Educational Background
B.Sc. Balıkesir University, Turkey, Mechanical Engineering, 2006
M.Sc. University of Leicester, UK, Mechanical Engineering, 2009
Ph.D. University of Leicester, UK, Mechanical Engineering, 2013
Research Interests
- Light alloys
- Composite materials
- Metal matrix composites/nanomaterials
- Manufacturing processes (casting, semi-solid metal forming)
- Mechanical testing
- Materials Characterization
- Advanced electron microscopy
- Tribology
- +90 232 750 6787
- +90 232 750 6701
- Mechanical Engineering Building (Z16)
Publications
2025 |
Hayta, Yiğit; Kandemir, Sinan Fatigue Assessment of Copper-Brazed Stainless-Steel Joints for Plate Heat Exchangers Journal Article 48 (2), pp. 725 – 737, 2025. @article{Hayta2025725, title = {Fatigue Assessment of Copper-Brazed Stainless-Steel Joints for Plate Heat Exchangers}, author = {Yiğit Hayta and Sinan Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85209070873&doi=10.1111%2fffe.14509&partnerID=40&md5=26b8fe46500ba5a9c9fc181fe0d129b6}, doi = {10.1111/ffe.14509}, year = {2025}, date = {2025-01-01}, volume = {48}, number = {2}, pages = {725 – 737}, abstract = {Cyclic pressures can cause fatigue failure in the brazed joints and plates of the plate heat exchangers (PHEs). This study examines the fatigue behavior of PHEs made from 316L and 304L steels brazed with copper foils employing strain-controlled fatigue tests to explore if 304L could replace 316L in the existing production line for cost reduction. Fatigue tests were conducted at four different load levels with a stress ratio of zero and a frequency of 5 Hz. Finite Element Analysis was used to assess strain distribution and estimate PHE lifespan based on generated strain versus number of cycles to failure curves. The microstructural analysis revealed that copper diffuses more easily into 316L than 304L, and using 50 μm thick foil causes more defects compared with 100 μm foil. It was shown that 316L joints have a significantly increased fatigue life compared with 304L. Both 316L and 304L met the 15-year lifetime requirement set by manufacturers. © 2024 The Author(s). Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Cyclic pressures can cause fatigue failure in the brazed joints and plates of the plate heat exchangers (PHEs). This study examines the fatigue behavior of PHEs made from 316L and 304L steels brazed with copper foils employing strain-controlled fatigue tests to explore if 304L could replace 316L in the existing production line for cost reduction. Fatigue tests were conducted at four different load levels with a stress ratio of zero and a frequency of 5 Hz. Finite Element Analysis was used to assess strain distribution and estimate PHE lifespan based on generated strain versus number of cycles to failure curves. The microstructural analysis revealed that copper diffuses more easily into 316L than 304L, and using 50 μm thick foil causes more defects compared with 100 μm foil. It was shown that 316L joints have a significantly increased fatigue life compared with 304L. Both 316L and 304L met the 15-year lifetime requirement set by manufacturers. © 2024 The Author(s). Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd. |
2024 |
Atasoy, Şahin; Kandemir, Sinan Machinability investigation on CNC milling of recycled short carbon fiber reinforced magnesium matrix composites Journal Article 11 (12), 2024. @article{Atasoy2024, title = {Machinability investigation on CNC milling of recycled short carbon fiber reinforced magnesium matrix composites}, author = {Şahin Atasoy and Sinan Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85211321447&doi=10.1088%2f2053-1591%2fad966b&partnerID=40&md5=8fc4c5413c9d7fcca20d1cc9f2e2961c}, doi = {10.1088/2053-1591/ad966b}, year = {2024}, date = {2024-01-01}, volume = {11}, number = {12}, abstract = {This study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480-560-640mmin?1) and feed rates (0.65-0.8-0.95mmmin?1). The experimental design was based on the Taguchi L9 (33) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for the 5 wt% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations. © 2024 The Author(s).}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480-560-640mmin?1) and feed rates (0.65-0.8-0.95mmmin?1). The experimental design was based on the Taguchi L9 (33) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for the 5 wt% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations. © 2024 The Author(s). |
Kandemir, Sinan; Yöyler, Sibel; Kumar, Rahul; Antonov, Maksim; Dieringa, Hajo 12 (2), 2024. @article{Kandemir2024, title = {Effect of Graphene Nanoplatelet Content on Mechanical and Elevated-Temperature Tribological Performance of Self-Lubricating ZE10 Magnesium Alloy Nanocomposites}, author = {Sinan Kandemir and Sibel Yöyler and Rahul Kumar and Maksim Antonov and Hajo Dieringa}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85187279959&doi=10.3390%2flubricants12020052&partnerID=40&md5=5aff0f7bd9e6d585a7baf38820d05dce}, doi = {10.3390/lubricants12020052}, year = {2024}, date = {2024-01-01}, volume = {12}, number = {2}, abstract = {Magnesium (Mg) and graphene in alloy formulations are of paramount importance for lightweight engineering applications. In the present study, ZE10 Mg-alloy-based nanocomposites reinforced with graphene nanoplatelets (GNPs) having a thickness of 10–20 nm were fabricated via ultrasound-assisted stir casting. The effect of GNP contents (0.25, 0.5, and 1.0 wt.%) on the microstructure, Vickers hardness, and tensile properties of nanocomposites was investigated. Further, tribological studies were performed under a ball-on-disc sliding wear configuration against a bearing ball counterbody, at room and elevated temperatures of 100 °C and 200 °C, to comprehend temperature-induced wear mechanisms and friction evolution. It was revealed that the GNP addition resulted in grain coarsening and increased porosity rate of the Mg alloy. While the composites exhibited improved hardness by 20–35% at room temperature and 100 °C, a minor change was observed in their hardness and tensile yield strength values at 200 °C with respect to the GNP-free alloy. A notable improvement in lowering and stabilizing friction (coefficient of friction at 200 °C~0.25) and wear values was seen for the self-lubricating GNP-added composites at all sliding temperatures. The worn surface morphology indicated a simultaneous occurrence of abrasive and adhesive wear mode in all samples at room temperature and 100 °C, while delamination and smearing along with debris compaction (tribolayer protection) were the dominant mechanisms of wear at 200 °C. Inclusively, the results advocate steady frictional conditions, improved wear resistance, and favorable wear-protective mechanisms for the Mg alloy–GNP nanocomposites at room and elevated temperatures. © 2024 by the authors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Magnesium (Mg) and graphene in alloy formulations are of paramount importance for lightweight engineering applications. In the present study, ZE10 Mg-alloy-based nanocomposites reinforced with graphene nanoplatelets (GNPs) having a thickness of 10–20 nm were fabricated via ultrasound-assisted stir casting. The effect of GNP contents (0.25, 0.5, and 1.0 wt.%) on the microstructure, Vickers hardness, and tensile properties of nanocomposites was investigated. Further, tribological studies were performed under a ball-on-disc sliding wear configuration against a bearing ball counterbody, at room and elevated temperatures of 100 °C and 200 °C, to comprehend temperature-induced wear mechanisms and friction evolution. It was revealed that the GNP addition resulted in grain coarsening and increased porosity rate of the Mg alloy. While the composites exhibited improved hardness by 20–35% at room temperature and 100 °C, a minor change was observed in their hardness and tensile yield strength values at 200 °C with respect to the GNP-free alloy. A notable improvement in lowering and stabilizing friction (coefficient of friction at 200 °C~0.25) and wear values was seen for the self-lubricating GNP-added composites at all sliding temperatures. The worn surface morphology indicated a simultaneous occurrence of abrasive and adhesive wear mode in all samples at room temperature and 100 °C, while delamination and smearing along with debris compaction (tribolayer protection) were the dominant mechanisms of wear at 200 °C. Inclusively, the results advocate steady frictional conditions, improved wear resistance, and favorable wear-protective mechanisms for the Mg alloy–GNP nanocomposites at room and elevated temperatures. © 2024 by the authors. |
2023 |
Kandemir, Sinan; Bohlen, Jan; Dieringa, Hajo Influence of recycled carbon fiber addition on the microstructure and creep response of extruded AZ91 magnesium alloy Journal Article Journal of Magnesium and Alloys, 11 (7), pp. 2518 – 2529, 2023, (All Open Access, Gold Open Access). @article{Kandemir20232518, title = {Influence of recycled carbon fiber addition on the microstructure and creep response of extruded AZ91 magnesium alloy}, author = {Sinan Kandemir and Jan Bohlen and Hajo Dieringa}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85166356480&doi=10.1016%2fj.jma.2023.06.004&partnerID=40&md5=c08bdbb377339cd4ef3e7fcae68561d5}, doi = {10.1016/j.jma.2023.06.004}, year = {2023}, date = {2023-01-01}, journal = {Journal of Magnesium and Alloys}, volume = {11}, number = {7}, pages = {2518 – 2529}, abstract = {In this study, the recycled short carbon fiber (CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion. The objective was to investigate the impact of CF content (2.5 and 5.0 wt.%) and fiber length (100 and 500 µm) on the microstructure, mechanical properties, and creep behavior of AZ91 alloy matrix. The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy. In comparison to the unreinforced AZ91 alloy, the composites with 2.5 wt.% CF exhibited an increase in hardness by 16–20% and yield strength by 5–15%, depending on the fiber length, while experiencing a reduction in ductility. When the reinforcement content was increased from 2.5 to 5.0 wt.%, strength values exhibited fluctuations and decline, accompanied by decreased ductility. These divergent outcomes were discussed in relation to fiber length, clustering tendency due to higher reinforcement content, and the presence of interfacial products with micro-cracks at the CF-matrix interface. Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy, suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep. © 2023}, note = {All Open Access, Gold Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the recycled short carbon fiber (CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion. The objective was to investigate the impact of CF content (2.5 and 5.0 wt.%) and fiber length (100 and 500 µm) on the microstructure, mechanical properties, and creep behavior of AZ91 alloy matrix. The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy. In comparison to the unreinforced AZ91 alloy, the composites with 2.5 wt.% CF exhibited an increase in hardness by 16–20% and yield strength by 5–15%, depending on the fiber length, while experiencing a reduction in ductility. When the reinforcement content was increased from 2.5 to 5.0 wt.%, strength values exhibited fluctuations and decline, accompanied by decreased ductility. These divergent outcomes were discussed in relation to fiber length, clustering tendency due to higher reinforcement content, and the presence of interfacial products with micro-cracks at the CF-matrix interface. Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy, suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep. © 2023 |
2021 |
Kangal, Serkan; Say, Harun A; Ayakda, Ozan; Kartav, Osman; Aydin, Levent; Artem, Secil H; Aktas, Engin; Yuceturk, Kutay; Tanoglu, Metin; Kandemir, Sinan; Beylergil, Bertan A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels Journal Article JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, 143 (4), 2021. @article{WOS:000669955100012, title = {A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels}, author = {Serkan Kangal and Harun A Say and Ozan Ayakda and Osman Kartav and Levent Aydin and Secil H Artem and Engin Aktas and Kutay Yuceturk and Metin Tanoglu and Sinan Kandemir and Bertan Beylergil}, doi = {10.1115/1.4049644}, year = {2021}, date = {2021-08-01}, journal = {JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, volume = {143}, number = {4}, abstract = {This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis. |
2017 |
Kandemir, Sinan Effects of TiB2 nanoparticle content on the microstructure and mechanical properties of aluminum matrix nanocomposites Journal Article MATERIALS TESTING, 59 (10), pp. 844-852, 2017, ISSN: 0025-5300. @article{ISI:000415695400003, title = {Effects of TiB2 nanoparticle content on the microstructure and mechanical properties of aluminum matrix nanocomposites}, author = {Sinan Kandemir}, doi = {10.3139/120.111079}, issn = {0025-5300}, year = {2017}, date = {2017-10-01}, journal = {MATERIALS TESTING}, volume = {59}, number = {10}, pages = {844-852}, abstract = {The present work reports the fabrication of A357 alloy matrix nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.-% TiB2 nanoparticles (20-30 nm) by a novel method which is the combination of semi-solid mechanical mixing and ultrasonic dispersion of nanoparticles in liquid state. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicated that reasonably effective deagglomeration and uniform distribution of TiB2 nanoparticles into the matrix were achieved. Transmission electron microscopy studies also confirmed that the nanoparticles were embedded into the matrix and a good bonding was obtained between the matrix and the reinforcement. Increasing nanoparticle content led to grain refinement and significant enhancement in the mechanical properties of nanocomposites. The addition of 0.5, 1.0, and 2.0 wt.-% TiB2 nanoparticles increased the 0.2 % proof stress of matrix alloy by approximately 31, 48 and 61 %, respectively. The contribution of different mechanisms to the strength enhancement is discussed. It is proposed that the strengthening is mainly due to Orowan mechanism and dislocation generation effect by the coefficient of thermal expansion mismatch between the TiB2 nanoparticles and the matrix.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present work reports the fabrication of A357 alloy matrix nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.-% TiB2 nanoparticles (20-30 nm) by a novel method which is the combination of semi-solid mechanical mixing and ultrasonic dispersion of nanoparticles in liquid state. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicated that reasonably effective deagglomeration and uniform distribution of TiB2 nanoparticles into the matrix were achieved. Transmission electron microscopy studies also confirmed that the nanoparticles were embedded into the matrix and a good bonding was obtained between the matrix and the reinforcement. Increasing nanoparticle content led to grain refinement and significant enhancement in the mechanical properties of nanocomposites. The addition of 0.5, 1.0, and 2.0 wt.-% TiB2 nanoparticles increased the 0.2 % proof stress of matrix alloy by approximately 31, 48 and 61 %, respectively. The contribution of different mechanisms to the strength enhancement is discussed. It is proposed that the strengthening is mainly due to Orowan mechanism and dislocation generation effect by the coefficient of thermal expansion mismatch between the TiB2 nanoparticles and the matrix. |
Kandemir, Sinan JOURNAL OF COMPOSITE MATERIALS, 51 (3), pp. 395-404, 2017, ISSN: 0021-9983. @article{ISI:000394801300009, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {Sinan Kandemir}, doi = {10.1177/0021998316644850}, issn = {0021-9983}, year = {2017}, date = {2017-02-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30nm) and aluminium powders (<75 mu m) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30nm) and aluminium powders (<75 mu m) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. |
2014 |
Kandemir, Sinan; Atkinson, Helen V; Weston, David P; Hainsworth, Sarah V METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 45A (12), pp. 5782-5798, 2014, ISSN: 1073-5623. @article{ISI:000342443200049, title = {Thixoforming of A356/SiC and A356/TiB2 Nanocomposites Fabricated by a Combination of Green Compact Nanoparticle Incorporation and Ultrasonic Treatment of the Melted Compact}, author = {Sinan Kandemir and Helen V Atkinson and David P Weston and Sarah V Hainsworth}, doi = {10.1007/s11661-014-2501-0}, issn = {1073-5623}, year = {2014}, date = {2014-11-01}, journal = {METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, volume = {45A}, number = {12}, pages = {5782-5798}, abstract = {Thixoforming is a type of semi-solid processing which is based on forming metals in the semi-solid state rather than fully liquid or solid state. There have been no reports of the thixoforming of nanocomposites in the literature. The incorporation of ceramic nanoparticles into liquid metals is a challenging task for the fabrication of metal matrix nanocomposites due to their large surface-to-volume ratio and poor wettability. Previous research work by a number of workers has highlighted the challenges with the incorporation of nanoparticles into liquid aluminum alloy. In the present study, SiC and TiB2 nanoparticles with an average diameter between 20 and 30 nm were firstly incorporated into green compacts by a powder forming route, and then the compacts were melted and treated ultrasonically. The microstructural studies reveal that the engulfment and relatively effective distribution of the nanoparticles into the melt were achieved. The hardness was considerably improved with only 0.8 wt pct addition of the nanoparticles. The nanocomposites were successfully thixoformed at a solid fraction between 0.65 and 0.70. The microstructures, hardness, and tensile mechanical properties of the thixoformed nanocomposites were investigated and compared with those of the as-received A356 and thixoformed A356 alloys. The tensile properties of the thixoformed nanocomposites were significantly enhanced compared to thixoformed A356 alloy without reinforcement, indicating the strengthening effects of the nanoparticles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thixoforming is a type of semi-solid processing which is based on forming metals in the semi-solid state rather than fully liquid or solid state. There have been no reports of the thixoforming of nanocomposites in the literature. The incorporation of ceramic nanoparticles into liquid metals is a challenging task for the fabrication of metal matrix nanocomposites due to their large surface-to-volume ratio and poor wettability. Previous research work by a number of workers has highlighted the challenges with the incorporation of nanoparticles into liquid aluminum alloy. In the present study, SiC and TiB2 nanoparticles with an average diameter between 20 and 30 nm were firstly incorporated into green compacts by a powder forming route, and then the compacts were melted and treated ultrasonically. The microstructural studies reveal that the engulfment and relatively effective distribution of the nanoparticles into the melt were achieved. The hardness was considerably improved with only 0.8 wt pct addition of the nanoparticles. The nanocomposites were successfully thixoformed at a solid fraction between 0.65 and 0.70. The microstructures, hardness, and tensile mechanical properties of the thixoformed nanocomposites were investigated and compared with those of the as-received A356 and thixoformed A356 alloys. The tensile properties of the thixoformed nanocomposites were significantly enhanced compared to thixoformed A356 alloy without reinforcement, indicating the strengthening effects of the nanoparticles. |
Lecturer Dr. Büşra Karaş
Erasmus Co-Coordinator
Educational Background
B.Sc. Eskisehir Osmangazi University, Turkey, Industrial Engineering, 2015
M.Sc. Newcastle University, United Kingdom, Design and Manufacturing Engineering, 2017
Ph.D. The University of Sheffield, United Kingdom, Mechanical Engineering, 2022
Research Interests
- Additive Manufacturing for Metals and Composites
- Manufacturing Processes
- Optimization of Production Systems
- Sustainability
- Cost Modelling
- +90 232 750 6783
- +90 232 750 6701
- Mechanical Engineering Building (Z15)
Prof. Dr. Gökhan Kiper
Minor Program Coordinator
Educational Background
B.Sc. Middle East Technical University, Turkey, Mechanical Engineering / Mathematics, 2004
M.Sc. Middle East Technical University, Turkey, Mechanical Engineering, 2006
Ph.D. Middle East Technical University, Turkey, Mechanical Engineering, 2011
Research Interests
- Mechanisms
- Deployable Structures
- Kinematics of Robotics
- Dynamics of Machinery
- +90 232 750 6777
- +90 232 750 6701
- Mechanical Engineering Building (Z14)
Publications
2025 |
Görgülü, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gökhan A new safe flexible torsion joint design with softening stiffness characteristics Journal Article 210 , 2025. @article{Görgülü2025, title = {A new safe flexible torsion joint design with softening stiffness characteristics}, author = {Ibrahimcan Görgülü and Mehmet Ismet Can Dede and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-105001995877&doi=10.1016%2fj.mechmachtheory.2025.106015&partnerID=40&md5=cfbbf7366b96aa9e72999c51346475de}, doi = {10.1016/j.mechmachtheory.2025.106015}, year = {2025}, date = {2025-01-01}, volume = {210}, abstract = {This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper introduces a novel flexible joint design that enhances mechanical versatility. The design shows how to obtain bidirectional deflections from a unidirectional spring. It enables the parallel and serial connections of springs. It features multiple stiffness regions determined by applied load levels, eliminating the need for a clutch mechanism. Mechanical limits can be added to customize stiffness, offering more hardening or softening regions. The design also allows for connecting multiple flexible joint units in series. In a case study, the series flexible joint design is developed with two flexible joint units, providing a softening stiffness characteristic. The joint has rigid, stiff, and soft regions. When used as a series elastic actuator in a robot manipulator, the rigid region aims to conduct the tasks at low torque levels, i.e., trajectory tracking. The stiff region is preserved for collaborative tasks in human–robot interaction, while the soft region enhances the robot's safety in case of control failure or collision. Static and dynamic test results comply with the ideal model. This flexible joint design improves mechanical performance, safety, and adaptability. © 2025 |
Paksoy, Erkan; Dede, Mehmet Ismet Can; Kiper, Gökhan Enhancing trajectory-tracking accuracy of high-acceleration parallel robots by predicting compliant displacements Journal Article 2025. @article{Paksoy2025, title = {Enhancing trajectory-tracking accuracy of high-acceleration parallel robots by predicting compliant displacements}, author = {Erkan Paksoy and Mehmet Ismet Can Dede and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85214919621&doi=10.1017%2fS0263574724002042&partnerID=40&md5=7bf7b46e48dd5459d472e74e623f469a}, doi = {10.1017/S0263574724002042}, year = {2025}, date = {2025-01-01}, abstract = {For precision-required robot operations, the robot's positioning accuracy, repeatability, and stiffness characteristics should be considered. If the mechanism has the desired repeatability performance, a kinematic calibration process can enhance the positioning accuracy. However, for robot operations where high accelerations are needed, the compliance characteristics of the mechanism affect the trajectory-tracking accuracy adversely. In this paper, a novel approach is proposed to enhance the trajectory-tracking accuracy of a robot operating at high accelerations by predicting the compliant displacements when there is no physical contact of the robot with its environment. Also, this case study compares the trajectory-tracking characteristics of an over-constrained and a normal-constrained 2-degrees-of-freedom (DoF) planar parallel mechanism during high-acceleration operations up to 5 g accelerations. In addition, the influence of the end-effector's center of mass (CoM) position along the normal of the plane is investigated in terms of its effects on the proposed trajectory-enhancing algorithm. © The Author(s), 2025. Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } For precision-required robot operations, the robot's positioning accuracy, repeatability, and stiffness characteristics should be considered. If the mechanism has the desired repeatability performance, a kinematic calibration process can enhance the positioning accuracy. However, for robot operations where high accelerations are needed, the compliance characteristics of the mechanism affect the trajectory-tracking accuracy adversely. In this paper, a novel approach is proposed to enhance the trajectory-tracking accuracy of a robot operating at high accelerations by predicting the compliant displacements when there is no physical contact of the robot with its environment. Also, this case study compares the trajectory-tracking characteristics of an over-constrained and a normal-constrained 2-degrees-of-freedom (DoF) planar parallel mechanism during high-acceleration operations up to 5 g accelerations. In addition, the influence of the end-effector's center of mass (CoM) position along the normal of the plane is investigated in terms of its effects on the proposed trajectory-enhancing algorithm. © The Author(s), 2025. Published by Cambridge University Press. |
2024 |
Liao, Yuan; Kiper, Gokhan; Krishnan, Sudarshan Mobility analysis of tripod scissor structures using screw theory Journal Article MECHANISM AND MACHINE THEORY, 191 , 2024. @article{WOS:001081762000001, title = {Mobility analysis of tripod scissor structures using screw theory}, author = {Yuan Liao and Gokhan Kiper and Sudarshan Krishnan}, doi = {10.1016/j.mechmachtheory.2023.105468}, year = {2024}, date = {2024-01-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {191}, abstract = {Mechanisms consisting of spatial scissor units have different kinematic behaviors than those of planar scissors. However, their kinematics, especially the mobility analysis, has not received enough attention. Two types of deployable asseblies are analyzed in this paper, namely the translational and mirrored assemblies. Both the assemblies are made of tripod scissor units, and their instantaneous mobility are examined using screw theory. The study starts on the configuration where all the members have the identical deployment angle. Firstly, the geometric property of each assembly was studied. Then, screw-loop equations were developed based on graph theory and closure equations. Finally, the mobility of each assembly was computed using linear algebra. Following the analysis, physical prototypes were constructed to validate the results, and several different motion modes were obtained for the translational assembly. The analysis reveals different kinematic behaviors of the two assemblies. In the given configuration, the translational assemblies have four instantaneous degrees of freedom, while the mirrored assemblies have only a single instantaneous degree of freedom.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mechanisms consisting of spatial scissor units have different kinematic behaviors than those of planar scissors. However, their kinematics, especially the mobility analysis, has not received enough attention. Two types of deployable asseblies are analyzed in this paper, namely the translational and mirrored assemblies. Both the assemblies are made of tripod scissor units, and their instantaneous mobility are examined using screw theory. The study starts on the configuration where all the members have the identical deployment angle. Firstly, the geometric property of each assembly was studied. Then, screw-loop equations were developed based on graph theory and closure equations. Finally, the mobility of each assembly was computed using linear algebra. Following the analysis, physical prototypes were constructed to validate the results, and several different motion modes were obtained for the translational assembly. The analysis reveals different kinematic behaviors of the two assemblies. In the given configuration, the translational assemblies have four instantaneous degrees of freedom, while the mirrored assemblies have only a single instantaneous degree of freedom. |
Atarer, Fulya; Kazanasmaz, Zehra Tuğçe; Korkmaz, Koray; Kiper, Gökhan Design Alternatives of Light Shelves using Altmann Linkage Journal Article 11 (2), pp. 391 – 407, 2024. @article{Atarer2024391, title = {Design Alternatives of Light Shelves using Altmann Linkage}, author = {Fulya Atarer and Zehra Tuğçe Kazanasmaz and Koray Korkmaz and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85217873829&doi=10.15627%2fjd.2024.26&partnerID=40&md5=b1f1dc67598ff3edc125d588a530acac}, doi = {10.15627/jd.2024.26}, year = {2024}, date = {2024-01-01}, volume = {11}, number = {2}, pages = {391 – 407}, abstract = {This paper proposes a novel new light shelf design with Altmann linkage using its kinetic principles: geometry and rotational angles. As previous studies explain a light shelf’s design in two ways: static and movable, the proposed one in this study has the potential to track the path of the sun due to its diagonal movement. The primary purpose is to direct the light shelf to intermediate directions, such as southeast and southwest, by utilizing the geometric properties of the Altmann linkage. The study explains how to dimension the links, calculate rotation angles, and model this device in Relux to test its daylight performance on specific dates in a year. A total of nine variations were analyzed during the three phases of design. They include shelf forms such as a rectangle, two rectangles, two squares, and varying link lengths, which define the distance to the windowsill. The final set of variations with two-square forms moving west and east successfully satisfied with sDA values as 71.52%, 72.99% (w), 75.92% (e); with ASE values as 8.83%, 8.56% (w), and 8.22% (e). This best design of Altmann linkage would be beneficial as an adaptive façade module that can direct daylight inside and achieve proper shading throughout the day and year. © 2024 The Author(s).}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper proposes a novel new light shelf design with Altmann linkage using its kinetic principles: geometry and rotational angles. As previous studies explain a light shelf’s design in two ways: static and movable, the proposed one in this study has the potential to track the path of the sun due to its diagonal movement. The primary purpose is to direct the light shelf to intermediate directions, such as southeast and southwest, by utilizing the geometric properties of the Altmann linkage. The study explains how to dimension the links, calculate rotation angles, and model this device in Relux to test its daylight performance on specific dates in a year. A total of nine variations were analyzed during the three phases of design. They include shelf forms such as a rectangle, two rectangles, two squares, and varying link lengths, which define the distance to the windowsill. The final set of variations with two-square forms moving west and east successfully satisfied with sDA values as 71.52%, 72.99% (w), 75.92% (e); with ASE values as 8.83%, 8.56% (w), and 8.22% (e). This best design of Altmann linkage would be beneficial as an adaptive façade module that can direct daylight inside and achieve proper shading throughout the day and year. © 2024 The Author(s). |
Kadak, Tarik; Kİper, Gökhan Function generation with planar four-bar mechanisms as a mixed problem of correlation of crank angles and dead center design Journal Article 49 (2), 2024. @article{Kadak2024, title = {Function generation with planar four-bar mechanisms as a mixed problem of correlation of crank angles and dead center design}, author = {Tarik Kadak and Gökhan Kİper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85190387912&doi=10.1007%2fs12046-024-02483-2&partnerID=40&md5=17b54a2c61741102b3bbb389a2b49952}, doi = {10.1007/s12046-024-02483-2}, year = {2024}, date = {2024-01-01}, volume = {49}, number = {2}, abstract = {Function generation synthesis of mechanisms can be considered as the design of correlation of crank angles and dead dead-center position design. These two problems have been clearly defined and solved separately. But some problems may require both correlation of crank angles and dead dead-center design at different configurations. Such problems are called mixed function generation problems. In this paper, an overview of these mixed function generation problems for the planar four-bar mechanism are given and the problems are solved analytically or semi-analytically. Except three of them, all presented mixed function generation problem formulations are novel. The solutions of all problems including three positions for the four-bar mechanism and the solution of a problem including four positions for a four-bar mechanism are addressed. All problems are first reduced to a univariate equation and a fast solution is found. Thus, link lengths can be found quickly by changing the problem definition problems, and several design iterations can be performed in a short time. Numerical solutions of all problems have been demonstrated using Excel. © Indian Academy of Sciences 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Function generation synthesis of mechanisms can be considered as the design of correlation of crank angles and dead dead-center position design. These two problems have been clearly defined and solved separately. But some problems may require both correlation of crank angles and dead dead-center design at different configurations. Such problems are called mixed function generation problems. In this paper, an overview of these mixed function generation problems for the planar four-bar mechanism are given and the problems are solved analytically or semi-analytically. Except three of them, all presented mixed function generation problem formulations are novel. The solutions of all problems including three positions for the four-bar mechanism and the solution of a problem including four positions for a four-bar mechanism are addressed. All problems are first reduced to a univariate equation and a fast solution is found. Thus, link lengths can be found quickly by changing the problem definition problems, and several design iterations can be performed in a short time. Numerical solutions of all problems have been demonstrated using Excel. © Indian Academy of Sciences 2024. |
Özen, Gülçin; Korkmaz, Koray; Ki̇Per, Gökhan DESIGN OF ROLLABLE RECIPROCAL FRAME NETWORK Journal Article 65 (1), pp. 15 – 26, 2024. @article{Özen202415, title = {DESIGN OF ROLLABLE RECIPROCAL FRAME NETWORK}, author = {Gülçin Özen and Koray Korkmaz and Gökhan Ki̇Per}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85191728751&doi=10.20898%2fj.iass.2023.030&partnerID=40&md5=35ea43833ea9a6c9fdb5ae5fc9a41e98}, doi = {10.20898/j.iass.2023.030}, year = {2024}, date = {2024-01-01}, volume = {65}, number = {1}, pages = {15 – 26}, abstract = {In the literature, reciprocal frames have been studied mostly for static structures. Studies on kinetic reciprocal frames are very limited. This study investigates two degrees-of-freedom reciprocal frame fans, and a novel deployable reciprocal frame network is obtained. While the network has a single degree-of-freedom in the cross-section, it has multi degrees-of-freedom in the longitudinal section. The network can be rolled to obtain a compact form and takes the form of a vault form when deployed. The way the nexors come together in the designed network is similar to the Da Vinci Bridge. The only difference is that cylindrical and prismatic joints are used in the intersection points to make the designed network deployable. Copyright © 2023 by Gülçin Özen,}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the literature, reciprocal frames have been studied mostly for static structures. Studies on kinetic reciprocal frames are very limited. This study investigates two degrees-of-freedom reciprocal frame fans, and a novel deployable reciprocal frame network is obtained. While the network has a single degree-of-freedom in the cross-section, it has multi degrees-of-freedom in the longitudinal section. The network can be rolled to obtain a compact form and takes the form of a vault form when deployed. The way the nexors come together in the designed network is similar to the Da Vinci Bridge. The only difference is that cylindrical and prismatic joints are used in the intersection points to make the designed network deployable. Copyright © 2023 by Gülçin Özen, |
Liao, Yuan; Kiper, Gökhan; Krishnan, Sudarshan Mobility analysis of tripod scissor structures using screw theory Journal Article 191 , 2024. @article{Liao2024, title = {Mobility analysis of tripod scissor structures using screw theory}, author = {Yuan Liao and Gökhan Kiper and Sudarshan Krishnan}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171620425&doi=10.1016%2fj.mechmachtheory.2023.105468&partnerID=40&md5=05fa84b35d19af08b1d1a4450146d4b0}, doi = {10.1016/j.mechmachtheory.2023.105468}, year = {2024}, date = {2024-01-01}, volume = {191}, abstract = {Mechanisms consisting of spatial scissor units have different kinematic behaviors than those of planar scissors. However, their kinematics, especially the mobility analysis, has not received enough attention. Two types of deployable assemblies are analyzed in this paper, namely the translational and mirrored assemblies. Both the assemblies are made of tripod scissor units, and their instantaneous mobility are examined using screw theory. The study starts on the configuration where all the members have the identical deployment angle. Firstly, the geometric property of each assembly was studied. Then, screw-loop equations were developed based on graph theory and closure equations. Finally, the mobility of each assembly was computed using linear algebra. Following the analysis, physical prototypes were constructed to validate the results, and several different motion modes were obtained for the translational assembly. The analysis reveals different kinematic behaviors of the two assemblies. In the given configuration, the translational assemblies have four instantaneous degrees of freedom, while the mirrored assemblies have only a single instantaneous degree of freedom. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mechanisms consisting of spatial scissor units have different kinematic behaviors than those of planar scissors. However, their kinematics, especially the mobility analysis, has not received enough attention. Two types of deployable assemblies are analyzed in this paper, namely the translational and mirrored assemblies. Both the assemblies are made of tripod scissor units, and their instantaneous mobility are examined using screw theory. The study starts on the configuration where all the members have the identical deployment angle. Firstly, the geometric property of each assembly was studied. Then, screw-loop equations were developed based on graph theory and closure equations. Finally, the mobility of each assembly was computed using linear algebra. Following the analysis, physical prototypes were constructed to validate the results, and several different motion modes were obtained for the translational assembly. The analysis reveals different kinematic behaviors of the two assemblies. In the given configuration, the translational assemblies have four instantaneous degrees of freedom, while the mirrored assemblies have only a single instantaneous degree of freedom. © 2023 Elsevier Ltd |
2023 |
Gorgulu, Ibrahimcan; Dede, Mehmet Ismet Can; Kiper, Gokhan Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism Journal Article MECHANISM AND MACHINE THEORY, 185 , 2023. @article{WOS:000966404700001, title = {Stiffness modeling of a 2-DoF over-constrained planar parallel mechanism}, author = {Ibrahimcan Gorgulu and Mehmet Ismet Can Dede and Gokhan Kiper}, doi = {10.1016/j.mechmachtheory.2023.105343}, year = {2023}, date = {2023-07-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {185}, abstract = {Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Stiffness model acquisition of over-constrained parallel mechanisms is relatively difficult since they have more than necessary kinematic loops. In this study, a stiffness modeling solution for over-constrained parallel mechanisms is proposed while considering the computational cost efficiency. Three contributions of the paper are: (1) Presenting the stiffness modeling procedure for serially connected closed-loop structures by using the Virtual Joint Method (2) Considering the effect of dynamic auxiliary forces and dynamic external forces on the mobile platform's deflection and achieving a direct solution by using superposition principle (3) A model fitting procedure for modifying the stiffness coefficients to comply with the experimental data. A 2 degrees-of-freedom over-constrained parallel mechanism is investigated as a case study. However, the proposed stiffness model is 6-DoF since compliant deflections occur in any direction. A finite element analysis and an experimental study verify the model's results. |
Aldanmaz, Ataol Behram; Ayit, Orhan; Kiper, Gökhan; Dede, Mehmet İsmet Can Gravity compensation of a 2R1T mechanism with remote center of motion for minimally invasive transnasal surgery applications Journal Article Robotica, 41 (3), pp. 807 – 820, 2023, (All Open Access, Green Open Access). @article{Aldanmaz2023807, title = {Gravity compensation of a 2R1T mechanism with remote center of motion for minimally invasive transnasal surgery applications}, author = {Ataol Behram Aldanmaz and Orhan Ayit and Gökhan Kiper and Mehmet İsmet Can Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85148022623&doi=10.1017%2fS0263574722000534&partnerID=40&md5=d9e00d3ba2c7864df127963817903586}, doi = {10.1017/S0263574722000534}, year = {2023}, date = {2023-01-01}, journal = {Robotica}, volume = {41}, number = {3}, pages = {807 – 820}, abstract = {This work addresses the gravity balancing of a 2R1T (2 rotations - 1 translation) mechanism with remote center of motion. A previously developed balancing solution is modified and applied to a prototype, and test results are presented. The mechanism is an endoscope holder for minimally invasive transnasal pituitary gland surgery. In this surgery, the endoscope is inserted through a nostril of the patient through a natural path to the pituitary gland. During the surgery, it is vital for the manipulator to be statically balanced so that in case of a motor failure, the patient is protected against any harmful motion of the endoscope. Additionally, static balancing takes the gravitational load from the actuators and hence facilitates the control of the mechanism. The mechanism is a 2URRR-URR type parallel manipulator with three legs. The payload mass is distributed to the legs on the sides. By using counter-masses for two links of each leg, the center of mass of each leg is lumped on the proximal link which simplifies the problem of balancing of a two degree-of-freedom inverted pendulum. The two proximal links with the lumped mass are statically balanced via springs. Dynamic simulations indicate that when the mechanism is statically balanced, generated actuator torques are reduced by 93.5%. Finally, the balancing solution is implemented on the prototype of the manipulator. The tests indicate that the manipulator is statically balanced within its task space when the actuators are disconnected. When the actuators are connected, the torque requirements decrease by about 37.8% with balancing. © The Author(s), 2022. Published by Cambridge University Press.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } This work addresses the gravity balancing of a 2R1T (2 rotations - 1 translation) mechanism with remote center of motion. A previously developed balancing solution is modified and applied to a prototype, and test results are presented. The mechanism is an endoscope holder for minimally invasive transnasal pituitary gland surgery. In this surgery, the endoscope is inserted through a nostril of the patient through a natural path to the pituitary gland. During the surgery, it is vital for the manipulator to be statically balanced so that in case of a motor failure, the patient is protected against any harmful motion of the endoscope. Additionally, static balancing takes the gravitational load from the actuators and hence facilitates the control of the mechanism. The mechanism is a 2URRR-URR type parallel manipulator with three legs. The payload mass is distributed to the legs on the sides. By using counter-masses for two links of each leg, the center of mass of each leg is lumped on the proximal link which simplifies the problem of balancing of a two degree-of-freedom inverted pendulum. The two proximal links with the lumped mass are statically balanced via springs. Dynamic simulations indicate that when the mechanism is statically balanced, generated actuator torques are reduced by 93.5%. Finally, the balancing solution is implemented on the prototype of the manipulator. The tests indicate that the manipulator is statically balanced within its task space when the actuators are disconnected. When the actuators are connected, the torque requirements decrease by about 37.8% with balancing. © The Author(s), 2022. Published by Cambridge University Press. |
Demirel, Murat; Kiper, Gökhan; Carbone, Giuseppe; Ceccarelli, Marco Design of a novel hybrid cable-constrained parallel leg mechanism for biped walking machines Journal Article Robotica, 41 (6), pp. 1778 – 1793, 2023, (All Open Access, Green Open Access). @article{Demirel20231778, title = {Design of a novel hybrid cable-constrained parallel leg mechanism for biped walking machines}, author = {Murat Demirel and Gökhan Kiper and Giuseppe Carbone and Marco Ceccarelli}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85182028851&doi=10.1017%2fS0263574723000140&partnerID=40&md5=60745b93d1c9dbaf0d172fdcc365338f}, doi = {10.1017/S0263574723000140}, year = {2023}, date = {2023-01-01}, journal = {Robotica}, volume = {41}, number = {6}, pages = {1778 – 1793}, abstract = {In this paper, a novel cable-constrained parallel mechanism is presented as a lightweight, low-cost leg mechanism design for walking machines to be used on flat surfaces. The proposed leg mechanism has three translational degrees of freedom. It is based on two specific hybrid kinematic topologies being herewith proposed. The paper reports the kinematic analysis formulation and a position performance evaluation to confirm the main characteristics of the proposed solutions. A 3D CAD model and simulations are carried out to demonstrate the feasibility of the proposed design for performing a human-like gait trajectory. A prototype has been built, and preliminarily tests have been conducted to confirm the motion capabilities of the proposed mechanism design. Then a second, enhanced prototype has been designed and built. An experimental validation is carried out for tracking a planar walking trajectory with the built prototypes by using a real-time PCI controller. Results are presented to validate the operation characteristics of the proposed mechanism and to prove its feasibility for legged walking machines. © The Author(s), 2023.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a novel cable-constrained parallel mechanism is presented as a lightweight, low-cost leg mechanism design for walking machines to be used on flat surfaces. The proposed leg mechanism has three translational degrees of freedom. It is based on two specific hybrid kinematic topologies being herewith proposed. The paper reports the kinematic analysis formulation and a position performance evaluation to confirm the main characteristics of the proposed solutions. A 3D CAD model and simulations are carried out to demonstrate the feasibility of the proposed design for performing a human-like gait trajectory. A prototype has been built, and preliminarily tests have been conducted to confirm the motion capabilities of the proposed mechanism design. Then a second, enhanced prototype has been designed and built. An experimental validation is carried out for tracking a planar walking trajectory with the built prototypes by using a real-time PCI controller. Results are presented to validate the operation characteristics of the proposed mechanism and to prove its feasibility for legged walking machines. © The Author(s), 2023. |
2022 |
Kiper, Gokhan; Korkmaz, Koray; Gur, Sebnem; Uncu, Mujde Yar; Maden, Feray; Akgun, Yenal; Karagoz, Cevahir Loop based classification of planar scissor linkages Journal Article SADHANA-ACADEMY PROCEEDINGS IN ENGINEERING SCIENCES, 47 (1), 2022. @article{WOS:000736787800002, title = {Loop based classification of planar scissor linkages}, author = {Gokhan Kiper and Koray Korkmaz and Sebnem Gur and Mujde Yar Uncu and Feray Maden and Yenal Akgun and Cevahir Karagoz}, doi = {10.1007/s12046-021-01783-1}, year = {2022}, date = {2022-03-01}, journal = {SADHANA-ACADEMY PROCEEDINGS IN ENGINEERING SCIENCES}, volume = {47}, number = {1}, abstract = {Scissor linkages have been used for several applications since ancient Greeks and Romans. In addition to simple scissor linkages with straight rods, linkages with angulated elements have been introduced in the last decades. In the related literature, two methods have been used to design scissor linkages, one of which is based on scissor elements, and the other is based on assembling loops. This study presents a systematic classification of scissor linkages as assemblies of rhombus, kite, dart, parallelogram and anti-parallelogram loops using frieze patterns and long-short diagonal connections. After the loops are replicated along a curve as a pattern, the linkages are obtained by selection of proper common link sections for adjacent loops. The resulting linkages are analyzed for their motions and they are classified as realizing scaling deployable, angular deployable or transformable motion. Some of the linkages obtained are novel. Totally 10 scalable deployable, 1 angular deployable and 8 transformable scissor linkages are listed. Designers in architecture and engineering can use this list of linkages as a library of scissor linkage topologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scissor linkages have been used for several applications since ancient Greeks and Romans. In addition to simple scissor linkages with straight rods, linkages with angulated elements have been introduced in the last decades. In the related literature, two methods have been used to design scissor linkages, one of which is based on scissor elements, and the other is based on assembling loops. This study presents a systematic classification of scissor linkages as assemblies of rhombus, kite, dart, parallelogram and anti-parallelogram loops using frieze patterns and long-short diagonal connections. After the loops are replicated along a curve as a pattern, the linkages are obtained by selection of proper common link sections for adjacent loops. The resulting linkages are analyzed for their motions and they are classified as realizing scaling deployable, angular deployable or transformable motion. Some of the linkages obtained are novel. Totally 10 scalable deployable, 1 angular deployable and 8 transformable scissor linkages are listed. Designers in architecture and engineering can use this list of linkages as a library of scissor linkage topologies. |
Maral, M O; Korkmaz, K; Kiper, G A NOVEL DESIGN METHOD OF DEPLOYABLE SEMI-REGULAR TESSELLATED SURFACES WITH PLANO-SPHERICAL UNITS Journal Article Journal of the International Association for Shell and Spatial Structures, 63 (3), pp. 189-202, 2022. @article{Maral2022189, title = {A NOVEL DESIGN METHOD OF DEPLOYABLE SEMI-REGULAR TESSELLATED SURFACES WITH PLANO-SPHERICAL UNITS}, author = {M O Maral and K Korkmaz and G Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85141332813&doi=10.20898%2fj.iass.2022.005&partnerID=40&md5=00e88391f1aab60b0932e2d29bdd5db2}, doi = {10.20898/j.iass.2022.005}, year = {2022}, date = {2022-01-01}, journal = {Journal of the International Association for Shell and Spatial Structures}, volume = {63}, number = {3}, pages = {189-202}, abstract = {The design of movable systems gives an opportunity to create transformable designs which respond to the environmental, functional, cultural, and aesthetical needs of today's architecture. This paper proposes a method for designing a family of deployable structures which can be applied to semi-regular tessellated planar surfaces such as roofs, walls, and shading devices. The generated modular approach and adaptability provides a wide usage area and various combinations for these designs. The regular convex polygon modules are designed as a network of the triangular units. The triangular unit is designed using Bennett's overconstrained plano-spherical linkage topology. The polygonal modules are assembled to each other in one-uniform semi-regular tessellations. The assembly of adjacent regular convex polygons in each tessellation is examined to find a proper solution for no collision during deployment and to properly fit a surface without any gaps or overlaps in the deployed position. The assembly method for creating 1-DoF deployable surfaces and mobility calculations for a unit, the polygonal modules, and the assemblies are computed, and motion studies are demonstrated with CAD models and exemplified for a square module for motion tests in a prototype. © 2022 by Mesude Oraj Maral, Koray Korkmaz and Gökhan Kiper.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The design of movable systems gives an opportunity to create transformable designs which respond to the environmental, functional, cultural, and aesthetical needs of today's architecture. This paper proposes a method for designing a family of deployable structures which can be applied to semi-regular tessellated planar surfaces such as roofs, walls, and shading devices. The generated modular approach and adaptability provides a wide usage area and various combinations for these designs. The regular convex polygon modules are designed as a network of the triangular units. The triangular unit is designed using Bennett's overconstrained plano-spherical linkage topology. The polygonal modules are assembled to each other in one-uniform semi-regular tessellations. The assembly of adjacent regular convex polygons in each tessellation is examined to find a proper solution for no collision during deployment and to properly fit a surface without any gaps or overlaps in the deployed position. The assembly method for creating 1-DoF deployable surfaces and mobility calculations for a unit, the polygonal modules, and the assemblies are computed, and motion studies are demonstrated with CAD models and exemplified for a square module for motion tests in a prototype. © 2022 by Mesude Oraj Maral, Koray Korkmaz and Gökhan Kiper. |
Özen, G; Kiper, G; Korkmaz, K DESIGN OF DEMOUNTABLE RECIPROCAL FRAMES WITH NEW GEOMETRIC PROPERTIES Journal Article Journal of the International Association for Shell and Spatial Structures, 63 (3), pp. 203-212, 2022. @article{Özen2022203, title = {DESIGN OF DEMOUNTABLE RECIPROCAL FRAMES WITH NEW GEOMETRIC PROPERTIES}, author = {G Özen and G Kiper and K Korkmaz}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85141307917&doi=10.20898%2fj.iass.2022.013&partnerID=40&md5=a0f27a35c8299c76151cffcb848aa678}, doi = {10.20898/j.iass.2022.013}, year = {2022}, date = {2022-01-01}, journal = {Journal of the International Association for Shell and Spatial Structures}, volume = {63}, number = {3}, pages = {203-212}, abstract = {This study aims to develop missing geometric knowledge for demountable reciprocal frames (RF). While designing a demountable RF, one should know the initial, in-process and final form of the RF. These processes require some specific geometric knowledge. There are some deficiencies about geometric properties in the previous studies about demountable RFs. In this study, the positions and the orientations of the nexors are found by using the Denavit-Hartenberg parameters. This information gives where the joints are placed, how they are oriented and take position according to one another. Besides, the influence of engagement length on the fan height and the base edge are analyzed. Thereby one will be able to find out how much space the RF covers with the known base edge. With the geometric knowledge obtained from this study, demountable RFs having different engagement lengths can be produced with the same nexors. Copyright © 2022 by Gülçin Özen, Gökhan Kiper and Koray Korkmaz.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study aims to develop missing geometric knowledge for demountable reciprocal frames (RF). While designing a demountable RF, one should know the initial, in-process and final form of the RF. These processes require some specific geometric knowledge. There are some deficiencies about geometric properties in the previous studies about demountable RFs. In this study, the positions and the orientations of the nexors are found by using the Denavit-Hartenberg parameters. This information gives where the joints are placed, how they are oriented and take position according to one another. Besides, the influence of engagement length on the fan height and the base edge are analyzed. Thereby one will be able to find out how much space the RF covers with the known base edge. With the geometric knowledge obtained from this study, demountable RFs having different engagement lengths can be produced with the same nexors. Copyright © 2022 by Gülçin Özen, Gökhan Kiper and Koray Korkmaz. |
Boztaş, S; Kiper, G Enumeration and instantaneous mobility analysis of a class of 3-UPU parallel manipulators with equilateral triangular platforms Journal Article Robotica, 40 (5), pp. 1538-1569, 2022. @article{Boztaş20221538, title = {Enumeration and instantaneous mobility analysis of a class of 3-UPU parallel manipulators with equilateral triangular platforms}, author = {S Boztaş and G Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85117189706&doi=10.1017%2fS0263574721001259&partnerID=40&md5=1f5d59f04a34765e2bd8e7c9809d9606}, doi = {10.1017/S0263574721001259}, year = {2022}, date = {2022-01-01}, journal = {Robotica}, volume = {40}, number = {5}, pages = {1538-1569}, abstract = {In this study, several joint axis orientations on equilateral platforms and the limbs of 3-UPU parallel manipulators (PMs) are examined. The generated joint layouts for the platforms were matched with each other to generate and enumerate manipulator architectures based on certain assumptions. The structures of thus obtained manipulators are examined and limb types were determined. These limb types were analyzed using screw theory. The instantaneous mobility of the manipulators and the motion characteristics of the moving platforms are tabulated. The finite mobility analysis of one of the manipulators is performed using a software package as an example. Among several different 3-UPU PM architectures, 118 novel 3-UPU PMs with non-parasitic 3-degrees-of-freedom are significantly important. The classified 3-UPU PMs with determined motion characteristics can be used by researchers as a design alternative for their specific design task. ©}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, several joint axis orientations on equilateral platforms and the limbs of 3-UPU parallel manipulators (PMs) are examined. The generated joint layouts for the platforms were matched with each other to generate and enumerate manipulator architectures based on certain assumptions. The structures of thus obtained manipulators are examined and limb types were determined. These limb types were analyzed using screw theory. The instantaneous mobility of the manipulators and the motion characteristics of the moving platforms are tabulated. The finite mobility analysis of one of the manipulators is performed using a software package as an example. Among several different 3-UPU PM architectures, 118 novel 3-UPU PMs with non-parasitic 3-degrees-of-freedom are significantly important. The classified 3-UPU PMs with determined motion characteristics can be used by researchers as a design alternative for their specific design task. © |
2021 |
Kumtepe, Elvan Doğan; Kiper, Gökhan Design, prototyping and tests of a rollable ramp for temporary use Journal Article Sadhana - Academy Proceedings in Engineering Sciences, 46 (4), 2021. @article{DoğanKumtepe2021, title = {Design, prototyping and tests of a rollable ramp for temporary use}, author = {Elvan Doğan Kumtepe and Gökhan Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85118582555&doi=10.1007%2fs12046-021-01756-4&partnerID=40&md5=17fef753eb6120e9431bab50f4ce0492}, doi = {10.1007/s12046-021-01756-4}, year = {2021}, date = {2021-01-01}, journal = {Sadhana - Academy Proceedings in Engineering Sciences}, volume = {46}, number = {4}, abstract = {Portable ramps, used generally by wheelchair users, offer temporary solution to increase accessibility and mobility. Preferably these ramps should be compact and lightweight for ease of handling and storage. Different types of portable ramps in the market that are used by wheelchair users are generally made of aluminum and require several improvements, especially in terms of lightweight and compactness. Based on wheelchair users’ inclinations a compact and lightweight rollable ramp is designed in this study. A parametric model of the links of the ramp are derived and the rolled geometry is optimized using convex hull and smallest enclosing circle algorithms. The side bars of the links are designed and manufactured from aluminum and the load-bearing panels are manufactured from sandwich composite structures with honeycomb core. Strength calculations are performed analytically and also with finite-element analysis. After the design is finalized, a prototype is manufactured. The designed ramp is 15.4% more compact and has 18.9% less weight compared to the best rival product available in the market. Load tests and functional tests are performed with voluntary wheelchair users. Several positive feedbacks are received from the participants about the ramp being practical, easy to use and store, lightweight, advantage of the anti-slip surface. © 2021, Indian Academy of Sciences.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Portable ramps, used generally by wheelchair users, offer temporary solution to increase accessibility and mobility. Preferably these ramps should be compact and lightweight for ease of handling and storage. Different types of portable ramps in the market that are used by wheelchair users are generally made of aluminum and require several improvements, especially in terms of lightweight and compactness. Based on wheelchair users’ inclinations a compact and lightweight rollable ramp is designed in this study. A parametric model of the links of the ramp are derived and the rolled geometry is optimized using convex hull and smallest enclosing circle algorithms. The side bars of the links are designed and manufactured from aluminum and the load-bearing panels are manufactured from sandwich composite structures with honeycomb core. Strength calculations are performed analytically and also with finite-element analysis. After the design is finalized, a prototype is manufactured. The designed ramp is 15.4% more compact and has 18.9% less weight compared to the best rival product available in the market. Load tests and functional tests are performed with voluntary wheelchair users. Several positive feedbacks are received from the participants about the ramp being practical, easy to use and store, lightweight, advantage of the anti-slip surface. © 2021, Indian Academy of Sciences. |
Dede, M I C; Kiper, G; Ayav, T; Ozdemirel, B; Tatlıcıoglu, E; Hanalioglu, S; Işıkay, I; Berker, M Human–robot interfaces of the neuroboscope: A minimally invasive endoscopic pituitary tumor surgery robotic assistance system Journal Article Journal of Medical Devices, Transactions of the ASME, 15 (1), 2021. @article{Dede2021, title = {Human–robot interfaces of the neuroboscope: A minimally invasive endoscopic pituitary tumor surgery robotic assistance system}, author = {M I C Dede and G Kiper and T Ayav and B Ozdemirel and E Tatlıcıoglu and S Hanalioglu and I Işıkay and M Berker}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85107958529&doi=10.1115%2f1.4049394&partnerID=40&md5=975e1687eb1d91a0fe45def8948da24f}, doi = {10.1115/1.4049394}, year = {2021}, date = {2021-01-01}, journal = {Journal of Medical Devices, Transactions of the ASME}, volume = {15}, number = {1}, abstract = {Endoscopic endonasal surgery is a commonly practiced minimally invasive neurosurgical operation for the treatment of a wide range of skull base pathologies including pituitary tumors. A common shortcoming of this surgery is the necessity of a third hand when the endoscope has to be handled to allow active use of both hands of the main surgeon. The robot surgery assistant NeuRoboScope system has been developed to take over the endoscope from the main surgeon’s hand while providing the surgeon with the necessary means of controlling the location and direction of the endoscope. One of the main novelties of the NeuRoboScope system is its human–robot interface designs which regulate and facilitate the interaction between the surgeon and the robot assistant. The human–robot interaction design of the NeuRoboScope system is investigated in two domains: direct physical interaction (DPI) and master–slave teleoperation (MST). The user study indicating the learning curve and ease of use of the MST is given and this paper is concluded via providing the reader with an outlook of possible new human–robot interfaces for the robot assisted surgery systems. Copyright VC 2021 by ASME}, keywords = {}, pubstate = {published}, tppubtype = {article} } Endoscopic endonasal surgery is a commonly practiced minimally invasive neurosurgical operation for the treatment of a wide range of skull base pathologies including pituitary tumors. A common shortcoming of this surgery is the necessity of a third hand when the endoscope has to be handled to allow active use of both hands of the main surgeon. The robot surgery assistant NeuRoboScope system has been developed to take over the endoscope from the main surgeon’s hand while providing the surgeon with the necessary means of controlling the location and direction of the endoscope. One of the main novelties of the NeuRoboScope system is its human–robot interface designs which regulate and facilitate the interaction between the surgeon and the robot assistant. The human–robot interaction design of the NeuRoboScope system is investigated in two domains: direct physical interaction (DPI) and master–slave teleoperation (MST). The user study indicating the learning curve and ease of use of the MST is given and this paper is concluded via providing the reader with an outlook of possible new human–robot interfaces for the robot assisted surgery systems. Copyright VC 2021 by ASME |
2020 |
Yasir, Abdullah; Kiper, Gokhan; Dede, Can M I Kinematic design of a non-parasitic 2R1T parallel mechanism with remote center of motion to be used in minimally invasive surgery applications Journal Article MECHANISM AND MACHINE THEORY, 153 , 2020, ISSN: 0094-114X. @article{ISI:000566908100008, title = {Kinematic design of a non-parasitic 2R1T parallel mechanism with remote center of motion to be used in minimally invasive surgery applications}, author = {Abdullah Yasir and Gokhan Kiper and Can M I Dede}, doi = {10.1016/j.mechmachtheory.2020.104013}, issn = {0094-114X}, year = {2020}, date = {2020-11-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {153}, abstract = {In minimally invasive surgery applications, the use of robotic manipulators is becoming more and more common to enhance the precision of the operations and post-operative processes. Such operations are often performed through an incision port (a pivot point) on the patient's body. Since the end-effector (the handled surgical tool) move about the pivot point, the manipulator has to move about a remote center of motion. In this study, a 3-degrees-of-freedom parallel mechanism with 2R1T (R: rotation, T: translation) remote center of motion capability is presented for minimally invasive surgery applications. First, its kinematic structure is introduced. Then, its kinematic analysis is carried out by using a simplified kinematic model which consists of three intersecting planes. Then the dimensional design is done for the desired workspace and a simulation test is carried out to verify the kinematic formulations. Finally, the prototype of the final design is presented. (c) 2020 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In minimally invasive surgery applications, the use of robotic manipulators is becoming more and more common to enhance the precision of the operations and post-operative processes. Such operations are often performed through an incision port (a pivot point) on the patient's body. Since the end-effector (the handled surgical tool) move about the pivot point, the manipulator has to move about a remote center of motion. In this study, a 3-degrees-of-freedom parallel mechanism with 2R1T (R: rotation, T: translation) remote center of motion capability is presented for minimally invasive surgery applications. First, its kinematic structure is introduced. Then, its kinematic analysis is carried out by using a simplified kinematic model which consists of three intersecting planes. Then the dimensional design is done for the desired workspace and a simulation test is carried out to verify the kinematic formulations. Finally, the prototype of the final design is presented. (c) 2020 Elsevier Ltd. All rights reserved. |
2019 |
Gur, Sebnem; Korkmaz, Koray; Kiper, Gokhan DESIGN OF ANTI-PARALLELOGRAM LOOP ASSEMBLIES Journal Article JOURNAL OF THE INTERNATIONAL ASSOCIATION FOR SHELL AND SPATIAL STRUCTURES, 60 (3), pp. 232-240, 2019, ISSN: 1028-365X. @article{ISI:000488985500006, title = {DESIGN OF ANTI-PARALLELOGRAM LOOP ASSEMBLIES}, author = {Sebnem Gur and Koray Korkmaz and Gokhan Kiper}, doi = {10.20898/j.iass.2019.201.006}, issn = {1028-365X}, year = {2019}, date = {2019-09-01}, journal = {JOURNAL OF THE INTERNATIONAL ASSOCIATION FOR SHELL AND SPATIAL STRUCTURES}, volume = {60}, number = {3}, pages = {232-240}, abstract = {Scissor mechanisms are frequently used for deployable structures and many studies have been conducted on the subject. Most of the studies consider scissor units as modules in the design process. An alternative approach is to utilize loops as the modules for design. In this paper, the design alternatives of single degree-of-freedom planar linkages comprising anti-parallelogram loops using the loop assembly method is presented. First, scissor mechanisms are reviewed. Next, the types of four-bar loops and the resulting linkages in the literature are introduced and those which are yet to be explored, anti-parallelogram being one of them, are identified. Then the loop assembly method and the examples in the literature are reviewed. As a method to form as many alternatives as possible, symmetry operations are proposed. Suitable frieze symmetry groups utilized for obtaining the assemblies are explained and the anti-parallelogram loop patterns are derived. Next, the single degree-of-freedom linkages are obtained from the loop assemblies. Finally, a selection of the resulting linkages with novel properties are presented. This study shows that loop assemblies are efficient in systematic type synthesis of scissor linkages, some types of which could not be foreseen by using units as modules.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Scissor mechanisms are frequently used for deployable structures and many studies have been conducted on the subject. Most of the studies consider scissor units as modules in the design process. An alternative approach is to utilize loops as the modules for design. In this paper, the design alternatives of single degree-of-freedom planar linkages comprising anti-parallelogram loops using the loop assembly method is presented. First, scissor mechanisms are reviewed. Next, the types of four-bar loops and the resulting linkages in the literature are introduced and those which are yet to be explored, anti-parallelogram being one of them, are identified. Then the loop assembly method and the examples in the literature are reviewed. As a method to form as many alternatives as possible, symmetry operations are proposed. Suitable frieze symmetry groups utilized for obtaining the assemblies are explained and the anti-parallelogram loop patterns are derived. Next, the single degree-of-freedom linkages are obtained from the loop assemblies. Finally, a selection of the resulting linkages with novel properties are presented. This study shows that loop assemblies are efficient in systematic type synthesis of scissor linkages, some types of which could not be foreseen by using units as modules. |
Maden, Feray; Akgun, Yenal; Kiper, Gokhan; Gur, Sebnem; Yar, Mujde; Korkmaz, Koray A CRITICAL REVIEW ON CLASSIFICATION AND TERMINOLOGY OF SCISSOR STRUCTURES Journal Article JOURNAL OF THE INTERNATIONAL ASSOCIATION FOR SHELL AND SPATIAL STRUCTURES, 60 (1, SI), pp. 47-64, 2019, ISSN: 1028-365X. @article{ISI:000464014000005, title = {A CRITICAL REVIEW ON CLASSIFICATION AND TERMINOLOGY OF SCISSOR STRUCTURES}, author = {Feray Maden and Yenal Akgun and Gokhan Kiper and Sebnem Gur and Mujde Yar and Koray Korkmaz}, doi = {10.20898/j.iass.2019.199.029}, issn = {1028-365X}, year = {2019}, date = {2019-03-01}, journal = {JOURNAL OF THE INTERNATIONAL ASSOCIATION FOR SHELL AND SPATIAL STRUCTURES}, volume = {60}, number = {1, SI}, pages = {47-64}, abstract = {When the existing literature on the research of scissor structures is thoroughly investigated, it is seen that different researchers use different terminologies and classifications especially for the definition of the primary units and the motion type. Some of the studies define the whole geometry based on the geometric properties of the primary scissor units and the unit lines while some other studies define it according to the loops. All these studies use different names for similar elements. This article aims to review the literature on the classification and terminology of scissor structures and represent the state of art on the studies. Tables are represented showing all approaches in the literature. In addition, the article criticizes the missing points of each terminology and definition, and proposes some new terminology. In order to arrive at this aim, different definitions of the primary scissor units and motion types used in key studies in the literature are investigated thoroughly. With several examples, it is demonstrated that naming the scissor units according to the resulting motion type might be misleading and it is better to specify the motion type for the whole structure. A classification for transformation of planar curves is presented.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When the existing literature on the research of scissor structures is thoroughly investigated, it is seen that different researchers use different terminologies and classifications especially for the definition of the primary units and the motion type. Some of the studies define the whole geometry based on the geometric properties of the primary scissor units and the unit lines while some other studies define it according to the loops. All these studies use different names for similar elements. This article aims to review the literature on the classification and terminology of scissor structures and represent the state of art on the studies. Tables are represented showing all approaches in the literature. In addition, the article criticizes the missing points of each terminology and definition, and proposes some new terminology. In order to arrive at this aim, different definitions of the primary scissor units and motion types used in key studies in the literature are investigated thoroughly. With several examples, it is demonstrated that naming the scissor units according to the resulting motion type might be misleading and it is better to specify the motion type for the whole structure. A classification for transformation of planar curves is presented. |
2017 |
Kiper, Gokhan; Dede, Mehmet Ismet Can; Maaroof, Omar W; Ozkahya, Merve Function generation with two loop mechanisms using decomposition and correction method Journal Article MECHANISM AND MACHINE THEORY, 110 , pp. 16-26, 2017, ISSN: 0094-114X. @article{ISI:000394063500002, title = {Function generation with two loop mechanisms using decomposition and correction method}, author = {Gokhan Kiper and Mehmet Ismet Can Dede and Omar W Maaroof and Merve Ozkahya}, doi = {10.1016/j.mechmachtheory.2016.12.004}, issn = {0094-114X}, year = {2017}, date = {2017-04-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {110}, pages = {16-26}, abstract = {Method of decomposition has been successfully applied to function generation with multi-loop mechanisms. For a two-loop mechanism, a function y = f(x) can be decomposed into two as w = g(x) and y = h(w) = h(g(x)) = f(x). This study makes use of the method of decomposition for two loop mechanisms, where the errors from each loop are forced to match each other. In the first loop, which includes the input of the mechanism, the decomposed function (g) is generated and the resulting structural error is determined. Then, for the second loop, the desired output of the function (f) is considered as an input and the structural error of the decomposed function (g) is determined. By matching the obtained structural errors, the final error in the output of the mechanism is reduced. Three different correction methods are proposed. The first method has three precision points per loop, while the second method has four. In the third method, the extrema of the errors from both loops are matched. The methods are applied to a Watt II type planar six-bar linkage for demonstration. Several numerical examples are worked out and the results are compared with the results in the literature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Method of decomposition has been successfully applied to function generation with multi-loop mechanisms. For a two-loop mechanism, a function y = f(x) can be decomposed into two as w = g(x) and y = h(w) = h(g(x)) = f(x). This study makes use of the method of decomposition for two loop mechanisms, where the errors from each loop are forced to match each other. In the first loop, which includes the input of the mechanism, the decomposed function (g) is generated and the resulting structural error is determined. Then, for the second loop, the desired output of the function (f) is considered as an input and the structural error of the decomposed function (g) is determined. By matching the obtained structural errors, the final error in the output of the mechanism is reduced. Three different correction methods are proposed. The first method has three precision points per loop, while the second method has four. In the third method, the extrema of the errors from both loops are matched. The methods are applied to a Watt II type planar six-bar linkage for demonstration. Several numerical examples are worked out and the results are compared with the results in the literature. |
Atarer, F; Korkmaz, K; Kiper, G Design alternatives of network of Altmann linkages Journal Article International Journal of Computational Methods and Experimental Measurements, 5 (4), pp. 495-503, 2017. @article{Atarer2017495, title = {Design alternatives of network of Altmann linkages}, author = {F Atarer and K Korkmaz and G Kiper}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032291841&doi=10.2495%2fCMEM-V5-N4-495-503&partnerID=40&md5=21a0c6a12a4aa176556157e4d54db241}, doi = {10.2495/CMEM-V5-N4-495-503}, year = {2017}, date = {2017-01-01}, journal = {International Journal of Computational Methods and Experimental Measurements}, volume = {5}, number = {4}, pages = {495-503}, abstract = {This paper presents a method of building deployable network assemblies derived from the single degree of freedom (DoF) over constrained Altmann linkage as a basic module. The method is based on assembling linkages with common links and joints or overlapping with extra R or 2R joints. New loops are emerged with overlapping method. The networks created have a single DoF, are over-constrained and have both fully deployed and folded configurations. The computer-aided models (CAD) are used to demonstrate these derived novel mechanisms. © 2017 WIT Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a method of building deployable network assemblies derived from the single degree of freedom (DoF) over constrained Altmann linkage as a basic module. The method is based on assembling linkages with common links and joints or overlapping with extra R or 2R joints. New loops are emerged with overlapping method. The networks created have a single DoF, are over-constrained and have both fully deployed and folded configurations. The computer-aided models (CAD) are used to demonstrate these derived novel mechanisms. © 2017 WIT Press. |
Yar, M; Korkmaz, K; Kiper, G; Maden, F; Akgün, Y; Aktaş, E A novel planar scissor structure transforming between concave and convex configurations Journal Article International Journal of Computational Methods and Experimental Measurements, 5 (4), pp. 442-450, 2017. @article{Yar2017442, title = {A novel planar scissor structure transforming between concave and convex configurations}, author = {M Yar and K Korkmaz and G Kiper and F Maden and Y Akgün and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051112573&doi=10.2495%2fCMEM-V5-N4-442-450&partnerID=40&md5=66bb8193b18ce907397210d6eae8b8dc}, doi = {10.2495/CMEM-V5-N4-442-450}, year = {2017}, date = {2017-01-01}, journal = {International Journal of Computational Methods and Experimental Measurements}, volume = {5}, number = {4}, pages = {442-450}, abstract = {In this paper, a novel two-dimensional scissor structure that transforms between concave and convex configurations is presented. The structure is designed by a method of assembling kite or anti-kite loops in the flat configuration. Angulated units are generated from the assembled loops. Finally, a new angulated scissor unit is introduced in order to design the novel scissor structure. © 2017 WIT Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a novel two-dimensional scissor structure that transforms between concave and convex configurations is presented. The structure is designed by a method of assembling kite or anti-kite loops in the flat configuration. Angulated units are generated from the assembled loops. Finally, a new angulated scissor unit is introduced in order to design the novel scissor structure. © 2017 WIT Press. |
2016 |
Uzunoglu, Emre; Dede, Mehmet Ismet Can; Kiper, Gokhan Trajectory planning for a planar macro-micro manipulator of a laser-cutting machine Journal Article INDUSTRIAL ROBOT-THE INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH AND APPLICATION, 43 (5, SI), pp. 513-523, 2016, ISSN: 0143-991X. @article{ISI:000386142100009, title = {Trajectory planning for a planar macro-micro manipulator of a laser-cutting machine}, author = {Emre Uzunoglu and Mehmet Ismet Can Dede and Gokhan Kiper}, doi = {10.1108/IR-02-2016-0057}, issn = {0143-991X}, year = {2016}, date = {2016-01-01}, journal = {INDUSTRIAL ROBOT-THE INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH AND APPLICATION}, volume = {43}, number = {5, SI}, pages = {513-523}, abstract = {Purpose - In the industry, there is always a demand to shorten the task completion durations to maximize the efficiency of the operation. This work focuses on making use of a special type of kinematic redundancy, macro-micro manipulation, to minimize the task completion duration. The purpose of this paper is to develop the most convenient trajectory planner to be integrated with industrial computerized numerical control (CNC) systems to resolve kinematic redundancy for task duration minimization. Design/methodology/approach - A special type of kinematic redundancy is devised by using two kinematically different mechanisms that have different advantages, which are named as macro and micro mechanisms. In this case, the control design including the trajectory planning should be devised taking into account the distinct advantages of both mechanisms. A new trajectory planning algorithm is designed and used for the constructed planar laser-cutting machine, and some benchmark pieces are cut. Findings - Offline method has practical limitations for employment in a real case scenario such as assuming infinite jerk limits for each axis motion. This limitation was removed by using an online trajectory generation technique. Experimental test results indicate that the online trajectory planning technique developed for the macro-micro mechanism to shorten the task duration was successful. Practical implications - Although the new trajectory planning algorithm is implemented for a laser-cutting machine, it can also be used for other manufacturing systems that require higher acceleration and accuracy levels than the conventional machines. The new algorithm is compatible with the commercially available CNC systems. Originality/value - In this work, a new approach to reducing the task duration for planar machining operations was introduced by making use of macro-micro manipulation concept. The core novelty of the work is devising trajectory planning algorithms to get the most efficiency in terms of acceleration limits from a macro-micro manipulation while making these algorithms deployable to most of the CNC systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Purpose - In the industry, there is always a demand to shorten the task completion durations to maximize the efficiency of the operation. This work focuses on making use of a special type of kinematic redundancy, macro-micro manipulation, to minimize the task completion duration. The purpose of this paper is to develop the most convenient trajectory planner to be integrated with industrial computerized numerical control (CNC) systems to resolve kinematic redundancy for task duration minimization. Design/methodology/approach - A special type of kinematic redundancy is devised by using two kinematically different mechanisms that have different advantages, which are named as macro and micro mechanisms. In this case, the control design including the trajectory planning should be devised taking into account the distinct advantages of both mechanisms. A new trajectory planning algorithm is designed and used for the constructed planar laser-cutting machine, and some benchmark pieces are cut. Findings - Offline method has practical limitations for employment in a real case scenario such as assuming infinite jerk limits for each axis motion. This limitation was removed by using an online trajectory generation technique. Experimental test results indicate that the online trajectory planning technique developed for the macro-micro mechanism to shorten the task duration was successful. Practical implications - Although the new trajectory planning algorithm is implemented for a laser-cutting machine, it can also be used for other manufacturing systems that require higher acceleration and accuracy levels than the conventional machines. The new algorithm is compatible with the commercially available CNC systems. Originality/value - In this work, a new approach to reducing the task duration for planar machining operations was introduced by making use of macro-micro manipulation concept. The core novelty of the work is devising trajectory planning algorithms to get the most efficiency in terms of acceleration limits from a macro-micro manipulation while making these algorithms deployable to most of the CNC systems. |
2015 |
Kiper, Gokhan; Bilgincan, Tunc Function generation synthesis of spherical 5R mechanism with regional spacing and Chebyshev approximation Journal Article MECHANISM AND MACHINE THEORY, 90 , pp. 37-46, 2015, ISSN: 0094-114X. @article{ISI:000353985200003, title = {Function generation synthesis of spherical 5R mechanism with regional spacing and Chebyshev approximation}, author = {Gokhan Kiper and Tunc Bilgincan}, doi = {10.1016/j.mechmachtheory.2015.03.001}, issn = {0094-114X}, year = {2015}, date = {2015-08-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {90}, pages = {37-46}, abstract = {The Chebyshev approximation is well known to be applicable for the approximation of single input-single output functions by means of a function generator mechanism. The approximation method may be also applied to multi-input functions, although until recently, it was not used for function generation with multi-degrees-of-freedom mechanisms. In a recent study, the authors applied the approximation method to a two-degrees-of-freedom mechanism for the first time, however the selection and iteration of the design points at which the errors were minimized were not satisfactory. In this study, an alternative method of selection and iteration for these design points is introduced and the corresponding spacing is called the ``regional spacing''. As a case study for the application of the approximation of multi-input functions, a spherical 5R mechanism is used to generate a two input-single-output function. The input joints of the mechanism are selected as one of the fixed joints and the moving mid-joint, whereas the remaining fixed joint represents the output. The synthesis problem is analytically formulated and presented in polynomial form for five and six unknown parameters. The synthesis problem for five unknown parameters is illustrated as a numerical example. Regional spacing is used for the selection and iteration of design points for the synthesis. The Chebyshev approximation along with the Remez algorithm is utilized to find the unknown construction parameters and the error of the function. The design points and the coefficients of the approximation polynomial are determined by numerical iteration using six moving points. At each iteration step, the design points are relocated at the extremum error points in their respective regions. Iterations are repeated until the magnitudes of the extremum point errors are approximately equal. Finally, the construction parameters of the mechanism are determined and the variation of the percentage error between the desired and generated function values is obtained. (C) 2015 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Chebyshev approximation is well known to be applicable for the approximation of single input-single output functions by means of a function generator mechanism. The approximation method may be also applied to multi-input functions, although until recently, it was not used for function generation with multi-degrees-of-freedom mechanisms. In a recent study, the authors applied the approximation method to a two-degrees-of-freedom mechanism for the first time, however the selection and iteration of the design points at which the errors were minimized were not satisfactory. In this study, an alternative method of selection and iteration for these design points is introduced and the corresponding spacing is called the ``regional spacing''. As a case study for the application of the approximation of multi-input functions, a spherical 5R mechanism is used to generate a two input-single-output function. The input joints of the mechanism are selected as one of the fixed joints and the moving mid-joint, whereas the remaining fixed joint represents the output. The synthesis problem is analytically formulated and presented in polynomial form for five and six unknown parameters. The synthesis problem for five unknown parameters is illustrated as a numerical example. Regional spacing is used for the selection and iteration of design points for the synthesis. The Chebyshev approximation along with the Remez algorithm is utilized to find the unknown construction parameters and the error of the function. The design points and the coefficients of the approximation polynomial are determined by numerical iteration using six moving points. At each iteration step, the design points are relocated at the extremum error points in their respective regions. Iterations are repeated until the magnitudes of the extremum point errors are approximately equal. Finally, the construction parameters of the mechanism are determined and the variation of the percentage error between the desired and generated function values is obtained. (C) 2015 Elsevier Ltd. All rights reserved. |
2014 |
Alizade, Rasim I; Kiper, Gokhan; Bagdadioglu, Baris; Dede, Can M I Function synthesis of Bennett 6R mechanisms using Chebyshev approximation Journal Article MECHANISM AND MACHINE THEORY, 81 , pp. 62-78, 2014, ISSN: 0094-114X. @article{ISI:000341141400006, title = {Function synthesis of Bennett 6R mechanisms using Chebyshev approximation}, author = {Rasim I Alizade and Gokhan Kiper and Baris Bagdadioglu and Can M I Dede}, doi = {10.1016/j.mechmachtheory.2014.06.010}, issn = {0094-114X}, year = {2014}, date = {2014-11-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {81}, pages = {62-78}, abstract = {This study focuses on approximate function synthesis of the three types of overconstrained Bennett 6R mechanisms using Chebyshev approximation. The three mechanisms are the double-planar, double-spherical and the plano-spherical 6R linkages. The single-loop 6R mechanisms are dissected into two imaginary loops and function synthesis is performed for both loops. First, the link lengths are employed as construction parameters of the mechanism. Then extra construction parameters for the input or output joint variables are introduced in order to increase the design points and hence enhance the accuracy of approximation. The synthesis formulations are applied computationally as case studies. The case studies illustrate how a designer can compare the three types of Bennett 6R mechanisms for the same function. Also we present a comparison of the spherical four-bar with the double-spherical 6R mechanism and show that the accuracy is improved when the 6R linkage is used. (C) 2014 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study focuses on approximate function synthesis of the three types of overconstrained Bennett 6R mechanisms using Chebyshev approximation. The three mechanisms are the double-planar, double-spherical and the plano-spherical 6R linkages. The single-loop 6R mechanisms are dissected into two imaginary loops and function synthesis is performed for both loops. First, the link lengths are employed as construction parameters of the mechanism. Then extra construction parameters for the input or output joint variables are introduced in order to increase the design points and hence enhance the accuracy of approximation. The synthesis formulations are applied computationally as case studies. The case studies illustrate how a designer can compare the three types of Bennett 6R mechanisms for the same function. Also we present a comparison of the spherical four-bar with the double-spherical 6R mechanism and show that the accuracy is improved when the 6R linkage is used. (C) 2014 Elsevier Ltd. All rights reserved. |
2013 |
Kiper, G; Söylemez, E Polyhedral linkages obtained as assemblies of planar link groups Journal Article Frontiers of Mechanical Engineering, 8 (1), pp. 3-9, 2013. @article{Kiper20133, title = {Polyhedral linkages obtained as assemblies of planar link groups}, author = {G Kiper and E Söylemez}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874799475&doi=10.1007%2fs11465-013-0363-6&partnerID=40&md5=f3339513404eac12eb100881e2c6ac47}, doi = {10.1007/s11465-013-0363-6}, year = {2013}, date = {2013-01-01}, journal = {Frontiers of Mechanical Engineering}, volume = {8}, number = {1}, pages = {3-9}, abstract = {The study aims to devise means of obtaining polyhedral linkages for homothetic deployment of polyhedral shapes by embedding planar link groups in faces of the polyhedral shape of interest. The questions of which polyhedral shapes may be suitable for such a purpose and what are the compatibility conditions for spatially assembling planar link groups are addressed. Homohedral and tangential polyhedral shapes are found to be suitable for the task and some examples of linkages are worked out. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The study aims to devise means of obtaining polyhedral linkages for homothetic deployment of polyhedral shapes by embedding planar link groups in faces of the polyhedral shape of interest. The questions of which polyhedral shapes may be suitable for such a purpose and what are the compatibility conditions for spatially assembling planar link groups are addressed. Homohedral and tangential polyhedral shapes are found to be suitable for the task and some examples of linkages are worked out. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg. |
Kiper, Gökhan; Bilgincan, Tunç; Dede, Mehmet İsmet Can Function generation synthesis of planar 5R mechanism Journal Article 2013. @article{kiper2013function, title = {Function generation synthesis of planar 5R mechanism}, author = {Gökhan Kiper and Tunç Bilgincan and Mehmet İsmet Can Dede}, url = {http://hdl.handle.net/11147/4217}, year = {2013}, date = {2013-01-01}, publisher = {IFToMM}, abstract = {This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined. |
2012 |
Kiper, Gökhan; Soylemez, Eres Homothetic Jitterbug-like linkages Journal Article MECHANISM AND MACHINE THEORY, 51 , pp. 145-158, 2012, ISSN: 0094-114X. @article{ISI:000300618000010, title = {Homothetic Jitterbug-like linkages}, author = {Gökhan Kiper and Eres Soylemez}, doi = {10.1016/j.mechmachtheory.2011.11.014}, issn = {0094-114X}, year = {2012}, date = {2012-05-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {51}, pages = {145-158}, abstract = {Conformal polyhedral linkages have drawn attention of scientists and engineers since the invention of Buckminster Fuller: a highly overconstrained spatial linkage, the Jitterbug. Many studies aimed to generalize Jitterbug-like linkages have been published, however a complete classification does not yet exist. This study introduces a definition for Jitterbug-like linkages and two major assumptions and then focuses on the properties of homothetic linkages. (C) 2011 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Conformal polyhedral linkages have drawn attention of scientists and engineers since the invention of Buckminster Fuller: a highly overconstrained spatial linkage, the Jitterbug. Many studies aimed to generalize Jitterbug-like linkages have been published, however a complete classification does not yet exist. This study introduces a definition for Jitterbug-like linkages and two major assumptions and then focuses on the properties of homothetic linkages. (C) 2011 Elsevier Ltd. All rights reserved. |
2010 |
Akgun, Yenal; Gantes, Charis J; Kalochairetis, Konstantinos E; Kiper, Gokhan A novel concept of convertible roofs with high transformability consisting of planar scissor-hinge structures Journal Article ENGINEERING STRUCTURES, 32 (9), pp. 2873-2883, 2010, ISSN: 0141-0296. @article{ISI:000281995300032, title = {A novel concept of convertible roofs with high transformability consisting of planar scissor-hinge structures}, author = {Yenal Akgun and Charis J Gantes and Konstantinos E Kalochairetis and Gokhan Kiper}, doi = {10.1016/j.engstruct.2010.05.006}, issn = {0141-0296}, year = {2010}, date = {2010-09-01}, journal = {ENGINEERING STRUCTURES}, volume = {32}, number = {9}, pages = {2873-2883}, abstract = {In this paper, a new adaptive scissor-hinge structure is introduced, which can be converted by means of actuators between a multitude of curvilinear arch-like shapes, where it can be stabilized and carry loads. The key point of this new structure is the proposed Modified Scissor-Like Element (M-SLE). With the development of this element, it becomes possible to change the geometry of the whole system without changing the dimensions of the struts or the span. The proposed scissor-hinge structure discussed here is planar, but it is also possible to combine structures in groups to create spatial systems. After outlining the differences of the proposed structure with existing designs, the dimensional properties of the M-SLE are introduced. Then, geometric principles and shape limitations of the whole structure are explained. Finally, structural analysis of the structure in different geometric configurations is performed, in order to discuss stiffness limitations associated with the advantage of increased mobility. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a new adaptive scissor-hinge structure is introduced, which can be converted by means of actuators between a multitude of curvilinear arch-like shapes, where it can be stabilized and carry loads. The key point of this new structure is the proposed Modified Scissor-Like Element (M-SLE). With the development of this element, it becomes possible to change the geometry of the whole system without changing the dimensions of the struts or the span. The proposed scissor-hinge structure discussed here is planar, but it is also possible to combine structures in groups to create spatial systems. After outlining the differences of the proposed structure with existing designs, the dimensional properties of the M-SLE are introduced. Then, geometric principles and shape limitations of the whole structure are explained. Finally, structural analysis of the structure in different geometric configurations is performed, in order to discuss stiffness limitations associated with the advantage of increased mobility. (C) 2010 Elsevier Ltd. All rights reserved. |
2008 |
Kiper, Gökhan; Soylemez, Eres; Kisisel, Özgür A U A family of deployable polygons and polyhedra Journal Article MECHANISM AND MACHINE THEORY, 43 (5), pp. 627-640, 2008, ISSN: 0094-114X. @article{ISI:000255728900007, title = {A family of deployable polygons and polyhedra}, author = {Gökhan Kiper and Eres Soylemez and Özgür A U Kisisel}, doi = {10.1016/j.mechmachtheory.2007.04.011}, issn = {0094-114X}, year = {2008}, date = {2008-05-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {43}, number = {5}, pages = {627-640}, abstract = {A new linkage type for resizing polygonal and polyhedral shapes is proposed. The single degree-of-freedom planar linkages considered mainly consist of links connected by revolute joints. It is shown that the group of mechanisms obtained realize Cardanic Motion. The polyhedral linkages proposed are constructed by implementing the proposed planar linkages on the faces and interconnecting them by links at the vertices to retain the solid angles of the polyhedral shape of interest. (C) 2007 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A new linkage type for resizing polygonal and polyhedral shapes is proposed. The single degree-of-freedom planar linkages considered mainly consist of links connected by revolute joints. It is shown that the group of mechanisms obtained realize Cardanic Motion. The polyhedral linkages proposed are constructed by implementing the proposed planar linkages on the faces and interconnecting them by links at the vertices to retain the solid angles of the polyhedral shape of interest. (C) 2007 Elsevier Ltd. All rights reserved. |
Res. Assist. Dr. Ayşe Korucu
Educational Background
B.Sc. Kocaeli University,Mechanical Engineering, 2007
M.Sc. Clemson University,Mechanical Engineering, 2011
Ph.D. Clemson University,Mechanical Engineering, 2016
Research Interests
- CFD
- Fluid Dynamics
- Turbulent Combustion Modeling
- +90 232 750 6759
- +90 232 750 6701
- Mechanical Engineering Building (Z27)
Publications
2024 |
Sarialtin, Huseyin; Korucu, Ayse Environmental assessment of the hydrogen combustion process in non-premixed gas turbines Journal Article INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 89 , pp. 135-141, 2024. @article{WOS:001327624500001, title = {Environmental assessment of the hydrogen combustion process in non-premixed gas turbines}, author = {Huseyin Sarialtin and Ayse Korucu}, doi = {10.1016/j.ijhydene.2024.09.219}, year = {2024}, date = {2024-11-01}, journal = {INTERNATIONAL JOURNAL OF HYDROGEN ENERGY}, volume = {89}, pages = {135-141}, abstract = {Using cleaner fuels, such as hydrogen and developing more efficient combustion technologies are crucial in reducing NOx and N2O emissions, contributing to environmental concerns like air pollution and global warming. However, studies focusing on gas turbines using H-2 as fuel often overlook the emissions resulting from H-2 combustion. Given that gas turbines play a significant role in electricity generation globally, even minor improvements in their efficiency can lead to substantial cumulative benefits. Therefore, this study aims to address this gap by conducting a comprehensive environmental assessment using the life cycle assessment (LCA) methodology. By evaluating the environmental impacts of emissions from the combustion process of a conventional gas turbine and comparing them with potential emissions from H(2)combustion, this research seeks to provide valuable insights into the overall environmental performance of these technologies and contribute to sustainable energy development efforts. There have already been several LCA studies on H-2 production. In this study, we have identified the potential emissions and environmental impacts of H-2 combustion in gas turbines and compared them with the impact values of H-2 production regarding reference studies. The result shows that emissions during combustion should be considered in the identified life cycle impact categories.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Using cleaner fuels, such as hydrogen and developing more efficient combustion technologies are crucial in reducing NOx and N2O emissions, contributing to environmental concerns like air pollution and global warming. However, studies focusing on gas turbines using H-2 as fuel often overlook the emissions resulting from H-2 combustion. Given that gas turbines play a significant role in electricity generation globally, even minor improvements in their efficiency can lead to substantial cumulative benefits. Therefore, this study aims to address this gap by conducting a comprehensive environmental assessment using the life cycle assessment (LCA) methodology. By evaluating the environmental impacts of emissions from the combustion process of a conventional gas turbine and comparing them with potential emissions from H(2)combustion, this research seeks to provide valuable insights into the overall environmental performance of these technologies and contribute to sustainable energy development efforts. There have already been several LCA studies on H-2 production. In this study, we have identified the potential emissions and environmental impacts of H-2 combustion in gas turbines and compared them with the impact values of H-2 production regarding reference studies. The result shows that emissions during combustion should be considered in the identified life cycle impact categories. |
Korucu, Ayse; Miller, Richard Differential diffusion and pressure effects on heavily sooting 2D Kerosene/Air shear flames Journal Article JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, 39 (1), pp. 91-99, 2024. @article{WOS:001058089000008, title = {Differential diffusion and pressure effects on heavily sooting 2D Kerosene/Air shear flames}, author = {Ayse Korucu and Richard Miller}, doi = {10.17341/gazimmfd.1153044}, year = {2024}, date = {2024-01-01}, journal = {JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY}, volume = {39}, number = {1}, pages = {91-99}, abstract = {Purpose: The current study aims to test the limits of the Unity Lewis number simplification coupled with both the ideal gas (IGL) and a real gas (RGL) equation of state (EOS) for predicting flame and soot characteristics of heavily sooting Kerosene/Air shear flames at 4 different operating pressures. Theory and Methods: Fully compressible Navier-Stokes equations are adopted in DNS environment. For the computational mesh, equivalently spaced grid points from 0 < x1 < L1 are used, while in the cross-stream direction the mesh has been stretched in the x2 direction. An 8th order central explicit finite difference method and a 4th order Runge-Kutta are employed to solve for the spatial and time derivatives, respectively. The temperature contour plot created using 2D DNS data are provided in Figure A. Boundary conditions of the problem: I -in x2 direction, far from the flame kernel, flow is set to have free stream characteristics and II -in x1 direction, periodic boundary conditions are embedded to solve the turbulent flow. Results: Comparisons to the earlier studies have been revealed that the mean peak flame temperature predictions done by the unity-Le number model are lessened; implying that the soot production/oxidation rates calculations will be debilitated comparably to the low mean flame temperature of the unity-Le number cases regardless of the operating pressure. The unity-Le number model's under-prediction of the flame temperatures results in intensifying incomplete combustion which not only emanates the soot load but also weaken the soot oxidation rate for the RGL EOS cases, while causes under-prediction of mass fraction of soot for the IGL EOS cases in comparison to the non-unity Le number results. As the operating pressure increases to 35 atm, the mean flame temperature increases hence, the soot load in the flame kernels increases even though the soot oxidation process is enhanced by the increasing flame temperature. An increase in the mean flame temperature has been noted for the IGL EOS model predictions at 35 atm case, which will cause an inevitable increment in soot load throughout the flame kernel. Conclusion: The analyses have revealed the that the unity-Le number simplification estimates the average flame temperature lower than expected for each operating pressure increasing the possibility of an incomplete combustion or even local flame weakening and extinction which stems `abnormally' high soot load throughout the flame kernel essentially for 10 and 35 atm operating pressure cases of the IGL EOS model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Purpose: The current study aims to test the limits of the Unity Lewis number simplification coupled with both the ideal gas (IGL) and a real gas (RGL) equation of state (EOS) for predicting flame and soot characteristics of heavily sooting Kerosene/Air shear flames at 4 different operating pressures. Theory and Methods: Fully compressible Navier-Stokes equations are adopted in DNS environment. For the computational mesh, equivalently spaced grid points from 0 < x1 < L1 are used, while in the cross-stream direction the mesh has been stretched in the x2 direction. An 8th order central explicit finite difference method and a 4th order Runge-Kutta are employed to solve for the spatial and time derivatives, respectively. The temperature contour plot created using 2D DNS data are provided in Figure A. Boundary conditions of the problem: I -in x2 direction, far from the flame kernel, flow is set to have free stream characteristics and II -in x1 direction, periodic boundary conditions are embedded to solve the turbulent flow. Results: Comparisons to the earlier studies have been revealed that the mean peak flame temperature predictions done by the unity-Le number model are lessened; implying that the soot production/oxidation rates calculations will be debilitated comparably to the low mean flame temperature of the unity-Le number cases regardless of the operating pressure. The unity-Le number model's under-prediction of the flame temperatures results in intensifying incomplete combustion which not only emanates the soot load but also weaken the soot oxidation rate for the RGL EOS cases, while causes under-prediction of mass fraction of soot for the IGL EOS cases in comparison to the non-unity Le number results. As the operating pressure increases to 35 atm, the mean flame temperature increases hence, the soot load in the flame kernels increases even though the soot oxidation process is enhanced by the increasing flame temperature. An increase in the mean flame temperature has been noted for the IGL EOS model predictions at 35 atm case, which will cause an inevitable increment in soot load throughout the flame kernel. Conclusion: The analyses have revealed the that the unity-Le number simplification estimates the average flame temperature lower than expected for each operating pressure increasing the possibility of an incomplete combustion or even local flame weakening and extinction which stems `abnormally' high soot load throughout the flame kernel essentially for 10 and 35 atm operating pressure cases of the IGL EOS model. |
2023 |
Benim, Ali Cemal; Korucu, Ayse Computational investigation of non-premixed hydrogen-air laminar flames Journal Article International Journal of Hydrogen Energy, 2023. @article{Benim2023, title = {Computational investigation of non-premixed hydrogen-air laminar flames}, author = {Ali Cemal Benim and Ayse Korucu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85146346018&doi=10.1016%2fj.ijhydene.2022.12.248&partnerID=40&md5=89d0b1a520d385f2e21b07190741c33b}, doi = {10.1016/j.ijhydene.2022.12.248}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Hydrogen Energy}, abstract = {Laminar diffusion hydrogen/air flames are numerically investigated. Detailed and global mechanisms are compared. NO formation is modelled by full nitrogen chemistry and the extended Zeldovich mechanism. A satisfactory agreement between the present predictions and the experiments of other authors is observed. Significance of different ingredients of mathematical modelling is analyzed. Minor roles of thermal diffusion and radiation, but a significant role of buoyancy is observed. It is observed that the full and quasi multi-component diffusion deliver the same results, whereas assuming Le = 1 to a remarkable difference. NO emissions logarithmically increase with increasing residence time. NO is the dominating nitrogen oxide. Its share increases with residence time, whereby NO2 and N2O show a reverse trend. It is observed that the NNH route plays a remarkable role in NO formation, where the share of the Zeldovich mechanism increases with residence time from about 20% to 85%, within the considered range. © 2022 Hydrogen Energy Publications LLC}, keywords = {}, pubstate = {published}, tppubtype = {article} } Laminar diffusion hydrogen/air flames are numerically investigated. Detailed and global mechanisms are compared. NO formation is modelled by full nitrogen chemistry and the extended Zeldovich mechanism. A satisfactory agreement between the present predictions and the experiments of other authors is observed. Significance of different ingredients of mathematical modelling is analyzed. Minor roles of thermal diffusion and radiation, but a significant role of buoyancy is observed. It is observed that the full and quasi multi-component diffusion deliver the same results, whereas assuming Le = 1 to a remarkable difference. NO emissions logarithmically increase with increasing residence time. NO is the dominating nitrogen oxide. Its share increases with residence time, whereby NO2 and N2O show a reverse trend. It is observed that the NNH route plays a remarkable role in NO formation, where the share of the Zeldovich mechanism increases with residence time from about 20% to 85%, within the considered range. © 2022 Hydrogen Energy Publications LLC |
Korucu, Ayşe; Miller, Richard Journal of the Faculty of Engineering and Architecture of Gazi University, 39 (1), pp. 91 – 99, 2023, (All Open Access, Bronze Open Access). @article{Korucu202391, title = {Differential diffusion and pressure effects on heavily sooting 2D Kerosene/Air shear flames; [Yüksek derecede kurum üreten 2B Gazyağı/Hava difüzyon alevleri üzerinde diferansiyel difüzyonun ve basıncın etkileri]}, author = {Ayşe Korucu and Richard Miller}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85174150376&doi=10.17341%2fgazimmfd.1153044&partnerID=40&md5=83c25552abccd22fffbfce453c52ba54}, doi = {10.17341/gazimmfd.1153044}, year = {2023}, date = {2023-01-01}, journal = {Journal of the Faculty of Engineering and Architecture of Gazi University}, volume = {39}, number = {1}, pages = {91 – 99}, abstract = {(Figure Presented). Purpose: The current study aims to test the limits of the Unity Lewis number simplification coupled with both the ideal gas (IGL) and a real gas (RGL) equation of state (EOS) for predicting flame and soot characteristics of heavily sooting Kerosene/Air shear flames at 4 different operating pressures. Theory and Methods: Fully compressible Navier-Stokes equations are adopted in DNS environment. For the computational mesh, equivalently spaced grid points from 0 < x1 < L1 are used, while in the cross-stream direction the mesh has been stretched in the x2 direction. An 8th order central explicit finite difference method and a 4th order Runge-Kutta are employed to solve for the spatial and time derivatives, respectively. The temperature contour plot created using 2D DNS data are provided in Figure A. Boundary conditions of the problem: I - in x2 direction, far from the flame kernel, flow is set to have free stream characteristics and II - in x1 direction, periodic boundary conditions are embedded to solve the turbulent flow. Results: Comparisons to the earlier studies have been revealed that the mean peak flame temperature predictions done by the unity-Le number model are lessened; implying that the soot production/oxidation rates calculations will be debilitated comparably to the low mean flame temperature of the unity-Le number cases regardless of the operating pressure. The unity-Le number model’s under-prediction of the flame temperatures results in intensifying incomplete combustion which not only emanates the soot load but also weaken the soot oxidation rate for the RGL EOS cases, while causes under-prediction of mass fraction of soot for the IGL EOS cases in comparison to the non-unity Le number results. As the operating pressure increases to 35 atm, the mean flame temperature increases hence, the soot load in the flame kernels increases even though the soot oxidation process is enhanced by the increasing flame temperature. An increase in the mean flame temperature has been noted for the IGL EOS model predictions at 35 atm case, which will cause an inevitable increment in soot load throughout the flame kernel. Conclusion: The analyses have revealed the that the unity-Le number simplification estimates the average flame temperature lower than expected for each operating pressure increasing the possibility of an incomplete combustion or even local flame weakening and extinction which stems ‘abnormally’ high soot load throughout the flame kernel essentially for 10 and 35 atm operating pressure cases of the IGL EOS model. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.}, note = {All Open Access, Bronze Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } (Figure Presented). Purpose: The current study aims to test the limits of the Unity Lewis number simplification coupled with both the ideal gas (IGL) and a real gas (RGL) equation of state (EOS) for predicting flame and soot characteristics of heavily sooting Kerosene/Air shear flames at 4 different operating pressures. Theory and Methods: Fully compressible Navier-Stokes equations are adopted in DNS environment. For the computational mesh, equivalently spaced grid points from 0 < x1 < L1 are used, while in the cross-stream direction the mesh has been stretched in the x2 direction. An 8th order central explicit finite difference method and a 4th order Runge-Kutta are employed to solve for the spatial and time derivatives, respectively. The temperature contour plot created using 2D DNS data are provided in Figure A. Boundary conditions of the problem: I - in x2 direction, far from the flame kernel, flow is set to have free stream characteristics and II - in x1 direction, periodic boundary conditions are embedded to solve the turbulent flow. Results: Comparisons to the earlier studies have been revealed that the mean peak flame temperature predictions done by the unity-Le number model are lessened; implying that the soot production/oxidation rates calculations will be debilitated comparably to the low mean flame temperature of the unity-Le number cases regardless of the operating pressure. The unity-Le number model’s under-prediction of the flame temperatures results in intensifying incomplete combustion which not only emanates the soot load but also weaken the soot oxidation rate for the RGL EOS cases, while causes under-prediction of mass fraction of soot for the IGL EOS cases in comparison to the non-unity Le number results. As the operating pressure increases to 35 atm, the mean flame temperature increases hence, the soot load in the flame kernels increases even though the soot oxidation process is enhanced by the increasing flame temperature. An increase in the mean flame temperature has been noted for the IGL EOS model predictions at 35 atm case, which will cause an inevitable increment in soot load throughout the flame kernel. Conclusion: The analyses have revealed the that the unity-Le number simplification estimates the average flame temperature lower than expected for each operating pressure increasing the possibility of an incomplete combustion or even local flame weakening and extinction which stems ‘abnormally’ high soot load throughout the flame kernel essentially for 10 and 35 atm operating pressure cases of the IGL EOS model. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved. |
2015 |
Ma, Zhiyuan; Korucu, Ayse; Miller, Richard Steven A priori analysis of subgrid scale pressure and heat flux in high pressure mixing and reacting shear layers Journal Article COMBUSTION THEORY AND MODELLING, 19 (6), pp. 807-832, 2015, ISSN: 1364-7830. @article{ISI:000366248600006, title = {A priori analysis of subgrid scale pressure and heat flux in high pressure mixing and reacting shear layers}, author = {Zhiyuan Ma and Ayse Korucu and Richard Steven Miller}, doi = {10.1080/13647830.2015.1100753}, issn = {1364-7830}, year = {2015}, date = {2015-11-01}, journal = {COMBUSTION THEORY AND MODELLING}, volume = {19}, number = {6}, pages = {807-832}, abstract = {Direct Numerical Simulation (DNS) data on high pressure H-2/O-2 and H-2/air flames using the compressible flow formulation, detailed kinetics, a real fluid equation of state, and generalised diffusion are analysed. The DNS is filtered over a range of filter widths to provide exact terms in the Large Eddy Simulation (LES) governing equations, including unclosed terms. The filtered pressure and the filtered heat flux vector are extensively compared with the pressure and the heat flux vector calculated as a function of the filtered primitive variables (i.e. the exact LES term is compared with its form available within an actual LES). The difference between these forms defines the subgrid pressure and the subgrid heat flux vector. The analyses are done both globally across the entire flame, as well as by conditionally averaging over specific regions of the flame; including regions of large subgrid kinetic energy, subgrid scalar dissipation, subgrid temperature variance, flame temperature, etc. In this work, although negligible for purely mixing cases, the gradient of the subgrid pressure is shown to be of the same order as, and larger than, the corresponding divergence of the turbulent subgrid stresses for reacting cases. This is despite the fact that all species behave essentially as ideal gases for this flame and holds true even when the ideal gas law is used to calculate the pressure. The ratio of the subgrid pressure gradient to the subgrid stress tensor divergence is shown to increase with increasing Reynolds number. Both the subgrid heat flux vector and its divergence are found to be substantially larger in reacting flows in comparison with mixing due to the associated larger temperature gradients. However, the divergence of the subgrid heat flux vector tends to be significantly smaller than other unclosed terms in the energy equation with decreasing significance with increasing Reynolds number.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Direct Numerical Simulation (DNS) data on high pressure H-2/O-2 and H-2/air flames using the compressible flow formulation, detailed kinetics, a real fluid equation of state, and generalised diffusion are analysed. The DNS is filtered over a range of filter widths to provide exact terms in the Large Eddy Simulation (LES) governing equations, including unclosed terms. The filtered pressure and the filtered heat flux vector are extensively compared with the pressure and the heat flux vector calculated as a function of the filtered primitive variables (i.e. the exact LES term is compared with its form available within an actual LES). The difference between these forms defines the subgrid pressure and the subgrid heat flux vector. The analyses are done both globally across the entire flame, as well as by conditionally averaging over specific regions of the flame; including regions of large subgrid kinetic energy, subgrid scalar dissipation, subgrid temperature variance, flame temperature, etc. In this work, although negligible for purely mixing cases, the gradient of the subgrid pressure is shown to be of the same order as, and larger than, the corresponding divergence of the turbulent subgrid stresses for reacting cases. This is despite the fact that all species behave essentially as ideal gases for this flame and holds true even when the ideal gas law is used to calculate the pressure. The ratio of the subgrid pressure gradient to the subgrid stress tensor divergence is shown to increase with increasing Reynolds number. Both the subgrid heat flux vector and its divergence are found to be substantially larger in reacting flows in comparison with mixing due to the associated larger temperature gradients. However, the divergence of the subgrid heat flux vector tends to be significantly smaller than other unclosed terms in the energy equation with decreasing significance with increasing Reynolds number. |
Assoc. Prof. Dr. Şenay Mihçin
Vice Chair
Educational Background
B.Sc. Middle East Technical University, Mechanical Engineering, 2001
M.Sc. Sabanci University- Leaders for Industry Program Double MSc in Mechatronics and Management Sciences, 2003
Ph.D. Computational Biomechanics, Loughborough University, United Kingdom, 2008
Research Interests
- Biomechancis, Validation, Verification
- Translational Research (Pre-Clinical)
- Motion Analysis, Simulations
- FE Modelling
- ISO 13485 Certifications
- Implant Design
- Crash Simulations
- +90 232 750 6701
- Mechanical Engineering Building (K1-13)
Publications
2024 |
Torabnia, Shams; Mihcin, Senay; Lazoglu, Ismail Design and manufacturing of a hip joint motion simulator with a novel modular design approach Journal Article 18 (1), pp. 401 – 417, 2024. @article{Torabnia2024401, title = {Design and manufacturing of a hip joint motion simulator with a novel modular design approach}, author = {Shams Torabnia and Senay Mihcin and Ismail Lazoglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171144946&doi=10.1007%2fs12008-023-01506-2&partnerID=40&md5=e978abee3f2263e3283041cbd26677ba}, doi = {10.1007/s12008-023-01506-2}, year = {2024}, date = {2024-01-01}, volume = {18}, number = {1}, pages = {401 – 417}, abstract = {The study is aimed to develop a hip joint wear simulator using a modular design approach to help experimentally monitor and control critical wear parameters to validate in-silico wear models. The proper control and application of wear parameters such as the range of motion, and the applied force values while estimating the lost material due to wear are essential for thorough analysis of wear phenomena for artificial joints. The simulator's dynamics were first modeled, then dynamic loading data was used to calculate the forces, which were further used for topology optimization to reduce the forces acting on each joint. The reduction of the link weights, connected to the actuators, intends to improve the quality of motion transferred to the femoral head. The modular design approach enables topology-optimized geometry, associated gravitational and dynamic forces, resulting in a cost-effective, energy-efficient product. Moreover, this design allows integration of the subject specific data by allowing different boundary conditions following the requirements of industry 5.0. Overall, the in-vitro motion stimulations of the hip-joint prosthesis and the modular design approach used in the study might help improve the accuracy and the effectiveness of wear simulations, which could lead into the development of better and longer-lasting joint prostheses for all. The subject-specific and society-based daily life data implemented as boundary conditions enable inclusion of the personalized effects. Next, with the results of the simulator, CEN Workshop Agreement (CWA) application is intended to cover the personalized effects for previously excluded populations, providing solution to inclusive design for all. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The study is aimed to develop a hip joint wear simulator using a modular design approach to help experimentally monitor and control critical wear parameters to validate in-silico wear models. The proper control and application of wear parameters such as the range of motion, and the applied force values while estimating the lost material due to wear are essential for thorough analysis of wear phenomena for artificial joints. The simulator's dynamics were first modeled, then dynamic loading data was used to calculate the forces, which were further used for topology optimization to reduce the forces acting on each joint. The reduction of the link weights, connected to the actuators, intends to improve the quality of motion transferred to the femoral head. The modular design approach enables topology-optimized geometry, associated gravitational and dynamic forces, resulting in a cost-effective, energy-efficient product. Moreover, this design allows integration of the subject specific data by allowing different boundary conditions following the requirements of industry 5.0. Overall, the in-vitro motion stimulations of the hip-joint prosthesis and the modular design approach used in the study might help improve the accuracy and the effectiveness of wear simulations, which could lead into the development of better and longer-lasting joint prostheses for all. The subject-specific and society-based daily life data implemented as boundary conditions enable inclusion of the personalized effects. Next, with the results of the simulator, CEN Workshop Agreement (CWA) application is intended to cover the personalized effects for previously excluded populations, providing solution to inclusive design for all. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature. |
Alpkaya, Alican Tuncay; Yılmaz, Mehmet; Şahin, Ahmet Mert; Mihçin, Dr. Şenay Investigation of stair ascending and descending activities on the lifespan of hip implants Journal Article 126 , 2024. @article{Alpkaya2024, title = {Investigation of stair ascending and descending activities on the lifespan of hip implants}, author = {Alican Tuncay Alpkaya and Mehmet Yılmaz and Ahmet Mert Şahin and Dr. Şenay Mihçin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85187165701&doi=10.1016%2fj.medengphy.2024.104142&partnerID=40&md5=2b0a204f6cdd05b3daeaa9175a00e1ea}, doi = {10.1016/j.medengphy.2024.104142}, year = {2024}, date = {2024-01-01}, volume = {126}, abstract = {Total hip arthroplasty (THA) surgeries among young patients are on the increase, so it is crucial to predict the lifespan of hip implants correctly and produce solutions to improve longevity. Current implants are designed and tested against walking conditions to predict the wear rates. However, it would be reasonable to include the additional effects of other daily life activities on wear rates to predict convergent results to clinical outputs. In this study, 14 participants are recruited to perform stair ascending (AS), descending (DS), and walking activities to obtain kinematic and kinetic data for each cycle using marker based Qualisys motion capture (MOCAP) system. AnyBody Modeling System using the Calibrated Anatomical System Technique (CAST) full body marker set are performed Multibody simulations. The 3D generic musculoskeletal model used in this study is a marker-based full-body motion capture model (AMMR,2.3.1 MoCapModel) consisting of the upper extremity and the Twente Lower Extremity Model (TLEM2). The dynamic wear prediction model detailing the intermittent and overall wear rates for CoCr-on-XLPE bearing couple is developed to investigate the wear mechanism under 3D loading for AS, DS, and walking activities over 5 million cycles (Mc) by using finite element modelling technique. The volumetric wear rates of XLPE liner under AS, DS, and walking activities over 5-Mc are predicted as 27.43, 23.22, and 18.84 mm3/Mc respectively. Additionally, the wear rate was predicted by combining stair activities and gait cycles based on the walk-to-stair ratio. By adding the effect of stair activities, the volumetric wear rate of XLPE is predicted as 22.02 mm3/Mc which is equivalent to 19.41% of walking. In conclusion, in this study, the effect of including other daily life activities is demonstrated and evidence is provided by matching them to the clinical data as opposed to simulator test results of implants under ISO 14242 boundary conditions. © 2024}, keywords = {}, pubstate = {published}, tppubtype = {article} } Total hip arthroplasty (THA) surgeries among young patients are on the increase, so it is crucial to predict the lifespan of hip implants correctly and produce solutions to improve longevity. Current implants are designed and tested against walking conditions to predict the wear rates. However, it would be reasonable to include the additional effects of other daily life activities on wear rates to predict convergent results to clinical outputs. In this study, 14 participants are recruited to perform stair ascending (AS), descending (DS), and walking activities to obtain kinematic and kinetic data for each cycle using marker based Qualisys motion capture (MOCAP) system. AnyBody Modeling System using the Calibrated Anatomical System Technique (CAST) full body marker set are performed Multibody simulations. The 3D generic musculoskeletal model used in this study is a marker-based full-body motion capture model (AMMR,2.3.1 MoCapModel) consisting of the upper extremity and the Twente Lower Extremity Model (TLEM2). The dynamic wear prediction model detailing the intermittent and overall wear rates for CoCr-on-XLPE bearing couple is developed to investigate the wear mechanism under 3D loading for AS, DS, and walking activities over 5 million cycles (Mc) by using finite element modelling technique. The volumetric wear rates of XLPE liner under AS, DS, and walking activities over 5-Mc are predicted as 27.43, 23.22, and 18.84 mm3/Mc respectively. Additionally, the wear rate was predicted by combining stair activities and gait cycles based on the walk-to-stair ratio. By adding the effect of stair activities, the volumetric wear rate of XLPE is predicted as 22.02 mm3/Mc which is equivalent to 19.41% of walking. In conclusion, in this study, the effect of including other daily life activities is demonstrated and evidence is provided by matching them to the clinical data as opposed to simulator test results of implants under ISO 14242 boundary conditions. © 2024 |
Chethan, K N; Waldschmidt, Nadine Schmidt Genannt; Corda, John Valerian; B, Satish Shenoy; Shetty, Sawan; Keni, Laxmikant G; N, Shyamasunder Bhat; Nikam, Nishant; Mihcin, Senay Patient-specific finite element analysis for assessing hip fracture risk in aging populations Journal Article 10 (3), 2024. @article{Chethan2024, title = {Patient-specific finite element analysis for assessing hip fracture risk in aging populations}, author = {K N Chethan and Nadine Schmidt Genannt Waldschmidt and John Valerian Corda and Satish Shenoy B and Sawan Shetty and Laxmikant G Keni and Shyamasunder Bhat N and Nishant Nikam and Senay Mihcin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85187550183&doi=10.1088%2f2057-1976%2fad2ff3&partnerID=40&md5=1f2f2b578ca65821da3b58f38b35de70}, doi = {10.1088/2057-1976/ad2ff3}, year = {2024}, date = {2024-01-01}, volume = {10}, number = {3}, abstract = {The femur is one of the most important bone in the human body, as it supports the body’s weight and helps with movement. The aging global population presents a significant challenge, leading to an increasing demand for artificial joints, particularly in knee and hip replacements, which are among the most prevalent surgical procedures worldwide. This study focuses on hip fractures, a common consequence of osteoporotic fractures in the elderly population. To accurately predict individual bone properties and assess fracture risk, patient-specific finite element models (FEM) were developed using CT data from healthy male individuals. The study employed ANSYS 2023 R2 software to estimate fracture loads under simulated single stance loading conditions, considering strain-based failure criteria. The FEM bone models underwent meticulous reconstruction, incorporating geometrical and mechanical properties crucial for fracture risk assessment. Results revealed an underestimation of the ultimate bearing capacity of bones, indicating potential fractures even during routine activities. The study explored variations in bone density, failure loads, and density/load ratios among different specimens, emphasizing the complexity of bone strength determination. Discussion of findings highlighted discrepancies between simulation results and previous studies, suggesting the need for optimization in modelling approaches. The strain-based yield criterion proved accurate in predicting fracture initiation but required adjustments for better load predictions. The study underscores the importance of refining density-elasticity relationships, investigating boundary conditions, and optimizing models through in vitro testing for enhanced clinical applicability in assessing hip fracture risk. In conclusion, this research contributes valuable insights into developing patient-specific FEM bone models for clinical hip fracture risk assessment, emphasizing the need for further refinement and optimization for accurate predictions and enhanced clinical utility. © 2024 The Author(s). Published by IOP Publishing Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The femur is one of the most important bone in the human body, as it supports the body’s weight and helps with movement. The aging global population presents a significant challenge, leading to an increasing demand for artificial joints, particularly in knee and hip replacements, which are among the most prevalent surgical procedures worldwide. This study focuses on hip fractures, a common consequence of osteoporotic fractures in the elderly population. To accurately predict individual bone properties and assess fracture risk, patient-specific finite element models (FEM) were developed using CT data from healthy male individuals. The study employed ANSYS 2023 R2 software to estimate fracture loads under simulated single stance loading conditions, considering strain-based failure criteria. The FEM bone models underwent meticulous reconstruction, incorporating geometrical and mechanical properties crucial for fracture risk assessment. Results revealed an underestimation of the ultimate bearing capacity of bones, indicating potential fractures even during routine activities. The study explored variations in bone density, failure loads, and density/load ratios among different specimens, emphasizing the complexity of bone strength determination. Discussion of findings highlighted discrepancies between simulation results and previous studies, suggesting the need for optimization in modelling approaches. The strain-based yield criterion proved accurate in predicting fracture initiation but required adjustments for better load predictions. The study underscores the importance of refining density-elasticity relationships, investigating boundary conditions, and optimizing models through in vitro testing for enhanced clinical applicability in assessing hip fracture risk. In conclusion, this research contributes valuable insights into developing patient-specific FEM bone models for clinical hip fracture risk assessment, emphasizing the need for further refinement and optimization for accurate predictions and enhanced clinical utility. © 2024 The Author(s). Published by IOP Publishing Ltd. |
2023 |
Mihcin, Senay; Sahin, Ahmet Mert; Yilmaz, Mehmet; Alpkaya, Alican Tuncay; Tuna, Merve; Akdeniz, Sevinc; Korkmaz, Nuray Can; Tosun, Aliye; Sahin, Serap Database covering the prayer movements which were not available previously Journal Article Scientific Data, 10 (1), 2023, (All Open Access, Gold Open Access, Green Open Access). @article{Mihcin2023, title = {Database covering the prayer movements which were not available previously}, author = {Senay Mihcin and Ahmet Mert Sahin and Mehmet Yilmaz and Alican Tuncay Alpkaya and Merve Tuna and Sevinc Akdeniz and Nuray Can Korkmaz and Aliye Tosun and Serap Sahin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85159738866&doi=10.1038%2fs41597-023-02196-x&partnerID=40&md5=04869d265c2a00af6d7e25dad86d8231}, doi = {10.1038/s41597-023-02196-x}, year = {2023}, date = {2023-01-01}, journal = {Scientific Data}, volume = {10}, number = {1}, abstract = {Lower body implants are designed according to the boundary conditions of gait data and tested against. However, due to diversity in cultural backgrounds, religious rituals might cause different ranges of motion and different loading patterns. Especially in the Eastern part of the world, diverse Activities of Daily Living (ADL) consist of salat, yoga rituals, and different style sitting postures. A database covering these diverse activities of the Eastern world is non-existent. This study focuses on data collection protocol and the creation of an online database of previously excluded ADL activities, targeting 200 healthy subjects via Qualisys and IMU motion capture systems, and force plates, from West and Middle East Asian populations with a special focus on the lower body joints. The current version of the database covers 50 volunteers for 13 different activities. The tasks are defined and listed in a table to create a database to search based on age, gender, BMI, type of activity, and motion capture system. The collected data is to be used for designing implants to allow these sorts of activities to be performed. © 2023, The Author(s).}, note = {All Open Access, Gold Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lower body implants are designed according to the boundary conditions of gait data and tested against. However, due to diversity in cultural backgrounds, religious rituals might cause different ranges of motion and different loading patterns. Especially in the Eastern part of the world, diverse Activities of Daily Living (ADL) consist of salat, yoga rituals, and different style sitting postures. A database covering these diverse activities of the Eastern world is non-existent. This study focuses on data collection protocol and the creation of an online database of previously excluded ADL activities, targeting 200 healthy subjects via Qualisys and IMU motion capture systems, and force plates, from West and Middle East Asian populations with a special focus on the lower body joints. The current version of the database covers 50 volunteers for 13 different activities. The tasks are defined and listed in a table to create a database to search based on age, gender, BMI, type of activity, and motion capture system. The collected data is to be used for designing implants to allow these sorts of activities to be performed. © 2023, The Author(s). |
Alpkaya, Alican Tuncay; Mihcin, Senay Dynamic computational wear model of PEEK-on-XLPE bearing couple in total hip replacements Journal Article Medical Engineering and Physics, 117 , 2023. @article{Alpkaya2023, title = {Dynamic computational wear model of PEEK-on-XLPE bearing couple in total hip replacements}, author = {Alican Tuncay Alpkaya and Senay Mihcin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85161750490&doi=10.1016%2fj.medengphy.2023.104006&partnerID=40&md5=37b73bc1035463a7dbadce39c74acb55}, doi = {10.1016/j.medengphy.2023.104006}, year = {2023}, date = {2023-01-01}, journal = {Medical Engineering and Physics}, volume = {117}, abstract = {Understanding wear mechanisms is a key factor to prevent primary failures causing revision surgery in total hip replacement (THR) applications. This study introduces a wear prediction model of (Polyetheretherketone) PEEK-on-XLPE (cross-linked polyethylene) bearing couple utilized to investigate the wear mechanism under 3D-gait cycle loading over 5 million cycles (Mc). A 32-mm PEEK femoral head and 4-mm thick XLPE bearing liner with a 3-mm PEEK shell are modeled in a 3D explicit finite element modeling (FEM) program. The volumetric and linear wear rates of XLPE liner per every million cycles were predicted as 1.965 mm3/Mc, and 0.0032 mm/Mc respectively. These results are consistent with the literature. PEEK-on-XLPE bearing couple exhibits a promising wear performance used in THR application. The wear pattern evolution of the model is similar to that of conventional polyethylene liners. Therefore, PEEK could be proposed as an alternative material to the CoCr head, especially used in XLPE-bearing couples. The wear prediction model could be utilized to improve the design parameters with the aim of prolonging the life span of hip implants. © 2023}, keywords = {}, pubstate = {published}, tppubtype = {article} } Understanding wear mechanisms is a key factor to prevent primary failures causing revision surgery in total hip replacement (THR) applications. This study introduces a wear prediction model of (Polyetheretherketone) PEEK-on-XLPE (cross-linked polyethylene) bearing couple utilized to investigate the wear mechanism under 3D-gait cycle loading over 5 million cycles (Mc). A 32-mm PEEK femoral head and 4-mm thick XLPE bearing liner with a 3-mm PEEK shell are modeled in a 3D explicit finite element modeling (FEM) program. The volumetric and linear wear rates of XLPE liner per every million cycles were predicted as 1.965 mm3/Mc, and 0.0032 mm/Mc respectively. These results are consistent with the literature. PEEK-on-XLPE bearing couple exhibits a promising wear performance used in THR application. The wear pattern evolution of the model is similar to that of conventional polyethylene liners. Therefore, PEEK could be proposed as an alternative material to the CoCr head, especially used in XLPE-bearing couples. The wear prediction model could be utilized to improve the design parameters with the aim of prolonging the life span of hip implants. © 2023 |
Torabnia, Shams; Mihcin, Senay; Lazoglu, Ismail Design and manufacturing of a hip joint motion simulator with a novel modular design approach Journal Article International Journal on Interactive Design and Manufacturing, 2023, (All Open Access, Green Open Access). @article{Torabnia2023, title = {Design and manufacturing of a hip joint motion simulator with a novel modular design approach}, author = {Shams Torabnia and Senay Mihcin and Ismail Lazoglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171144946&doi=10.1007%2fs12008-023-01506-2&partnerID=40&md5=e978abee3f2263e3283041cbd26677ba}, doi = {10.1007/s12008-023-01506-2}, year = {2023}, date = {2023-01-01}, journal = {International Journal on Interactive Design and Manufacturing}, abstract = {The study is aimed to develop a hip joint wear simulator using a modular design approach to help experimentally monitor and control critical wear parameters to validate in-silico wear models. The proper control and application of wear parameters such as the range of motion, and the applied force values while estimating the lost material due to wear are essential for thorough analysis of wear phenomena for artificial joints. The simulator's dynamics were first modeled, then dynamic loading data was used to calculate the forces, which were further used for topology optimization to reduce the forces acting on each joint. The reduction of the link weights, connected to the actuators, intends to improve the quality of motion transferred to the femoral head. The modular design approach enables topology-optimized geometry, associated gravitational and dynamic forces, resulting in a cost-effective, energy-efficient product. Moreover, this design allows integration of the subject specific data by allowing different boundary conditions following the requirements of industry 5.0. Overall, the in-vitro motion stimulations of the hip-joint prosthesis and the modular design approach used in the study might help improve the accuracy and the effectiveness of wear simulations, which could lead into the development of better and longer-lasting joint prostheses for all. The subject-specific and society-based daily life data implemented as boundary conditions enable inclusion of the personalized effects. Next, with the results of the simulator, CEN Workshop Agreement (CWA) application is intended to cover the personalized effects for previously excluded populations, providing solution to inclusive design for all. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } The study is aimed to develop a hip joint wear simulator using a modular design approach to help experimentally monitor and control critical wear parameters to validate in-silico wear models. The proper control and application of wear parameters such as the range of motion, and the applied force values while estimating the lost material due to wear are essential for thorough analysis of wear phenomena for artificial joints. The simulator's dynamics were first modeled, then dynamic loading data was used to calculate the forces, which were further used for topology optimization to reduce the forces acting on each joint. The reduction of the link weights, connected to the actuators, intends to improve the quality of motion transferred to the femoral head. The modular design approach enables topology-optimized geometry, associated gravitational and dynamic forces, resulting in a cost-effective, energy-efficient product. Moreover, this design allows integration of the subject specific data by allowing different boundary conditions following the requirements of industry 5.0. Overall, the in-vitro motion stimulations of the hip-joint prosthesis and the modular design approach used in the study might help improve the accuracy and the effectiveness of wear simulations, which could lead into the development of better and longer-lasting joint prostheses for all. The subject-specific and society-based daily life data implemented as boundary conditions enable inclusion of the personalized effects. Next, with the results of the simulator, CEN Workshop Agreement (CWA) application is intended to cover the personalized effects for previously excluded populations, providing solution to inclusive design for all. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature. |
Alpkaya, Alican Tuncay; Mihçin, Şenay The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement Journal Article Tribology Transactions, 66 (1), pp. 59 – 72, 2023. @article{Alpkaya202359, title = {The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement}, author = {Alican Tuncay Alpkaya and Şenay Mihçin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85144145526&doi=10.1080%2f10402004.2022.2140727&partnerID=40&md5=727b9b4294502f860c17ec5352419b28}, doi = {10.1080/10402004.2022.2140727}, year = {2023}, date = {2023-01-01}, journal = {Tribology Transactions}, volume = {66}, number = {1}, pages = {59 – 72}, abstract = {Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 (Formula presented.) for CoCr head and 21.0271 (Formula presented.) for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 (Formula presented.) for CoCr head and 1.8476 (Formula presented.) for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopaedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants. © 2022 Society of Tribologists and Lubrication Engineers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 (Formula presented.) for CoCr head and 21.0271 (Formula presented.) for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 (Formula presented.) for CoCr head and 1.8476 (Formula presented.) for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopaedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants. © 2022 Society of Tribologists and Lubrication Engineers. |
2022 |
Yu, Hao; Feng, Zhihong; Wang, Ling; Mihcin, Senay; Kang, Jianfeng; Bai, Shizhu; Zhao, Yimin Finite Element Study of PEEK Materials Applied in Post-Retained Restorations Journal Article POLYMERS, 14 (16), 2022. @article{WOS:000846652600001, title = {Finite Element Study of PEEK Materials Applied in Post-Retained Restorations}, author = {Hao Yu and Zhihong Feng and Ling Wang and Senay Mihcin and Jianfeng Kang and Shizhu Bai and Yimin Zhao}, doi = {10.3390/polym14163422}, year = {2022}, date = {2022-08-01}, journal = {POLYMERS}, volume = {14}, number = {16}, abstract = {Background: This study aimed to investigate the biomechanical behaviors of polyether ether ketone (PEEK) and traditional materials (titanium and fiber) when used to restore tooth defects in the form of prefabricated post or customized post via computational modelling. Methods: First, the prototype of natural tooth, and the prototypes of prefabricated post and customized post were established, respectively, whilst the residual root was restored with dentin ferrule using reverse engineering methods. Then, the stress and strain of CFR-PEEK (PEEK reinforced by 30% carbon fiber) and pure PEEK (PEEK without any reprocessing) post were compared with those made in traditional materials using the three-dimensional finite element method. Results: From the stress point of view, compared with metal and fiber posts, CFR-PEEK and pure PEEK prefabricated post both demonstrated reduced post-core interface stress, post stress, post-root cement stress and root cement stress; moreover, CFR-PEEK and pure PEEK customized post demonstrated reduced post stress, post-root cement stress and root cement stress, while the strain of CFR-PEEK post was the closest to that of dentin. Conclusions: Compared with the traditional posts, both the CFR-PEEK and pure PEEK posts could reduce the risk of debonding and vertical root fracture, whether they were used as prefabricated posts or customized posts, but the biomechanical behavior of carbon fiber-reinforced CFR-PEEK restorations was the closest to dentin, no matter if they were used as prefabricated post or customized post. Therefore, the CFR-PEEK post could be more suitable to restore massive tooth defects. Pure PEEK needs filler reinforcement to be used for post-retained restoration.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Background: This study aimed to investigate the biomechanical behaviors of polyether ether ketone (PEEK) and traditional materials (titanium and fiber) when used to restore tooth defects in the form of prefabricated post or customized post via computational modelling. Methods: First, the prototype of natural tooth, and the prototypes of prefabricated post and customized post were established, respectively, whilst the residual root was restored with dentin ferrule using reverse engineering methods. Then, the stress and strain of CFR-PEEK (PEEK reinforced by 30% carbon fiber) and pure PEEK (PEEK without any reprocessing) post were compared with those made in traditional materials using the three-dimensional finite element method. Results: From the stress point of view, compared with metal and fiber posts, CFR-PEEK and pure PEEK prefabricated post both demonstrated reduced post-core interface stress, post stress, post-root cement stress and root cement stress; moreover, CFR-PEEK and pure PEEK customized post demonstrated reduced post stress, post-root cement stress and root cement stress, while the strain of CFR-PEEK post was the closest to that of dentin. Conclusions: Compared with the traditional posts, both the CFR-PEEK and pure PEEK posts could reduce the risk of debonding and vertical root fracture, whether they were used as prefabricated posts or customized posts, but the biomechanical behavior of carbon fiber-reinforced CFR-PEEK restorations was the closest to dentin, no matter if they were used as prefabricated post or customized post. Therefore, the CFR-PEEK post could be more suitable to restore massive tooth defects. Pure PEEK needs filler reinforcement to be used for post-retained restoration. |
Mihcin, Senay BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK, 67 (3), pp. 185-199, 2022. @article{WOS:000796085500001, title = {Simultaneous validation of wearable motion capture system for lower body applications: over single plane range of motion (ROM) and gait activities}, author = {Senay Mihcin}, doi = {10.1515/bmt-2021-0429}, year = {2022}, date = {2022-06-01}, journal = {BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK}, volume = {67}, number = {3}, pages = {185-199}, abstract = {Extracting data from Zhu, 2019 #5 daily life activities is important in biomechanical applications to define exact boundary conditions for the intended use-based applications. Although optoelectronic camera-marker based systems are used as gold standard tools for medical applications, due to line-of-sight problem, there is a need for wearable, affordable motion capture (MOCAP) systems. We investigate the potential use of a wearable inertial measurement unit (IMU) based-wearable MOCAP system for biomechanical applications. The in vitro proof of concept is provided for the full lower body consisting of hip, knee, and ankle joints via controlled single-plane anatomical range of motion (ROM) simulations using an electrical motor, while collecting data simultaneously via opto-electronic markers and IMU sensors. On 15 healthy volunteers the flexion-extension, abduction-adduction, internal-external rotation (ROM) values of hip and, the flexion - extension ROM values of the knee and ankle joints are calculated for both systems. The Bland-Altman graphs showed promising agreement both for in vitro and in vivo experiments. The maximum Root Mean Square Errors (RMSE) between the systems in vitro was 3.4 degrees for hip and 5.9 degrees for knee flexion motion in vivo, respectively. The gait data of the volunteers were assessed between the heel strike and toe off events to investigate the limits of agreement, calculating the population averages and standard deviation for both systems over the gait cycle. The maximum difference was for the ankle joint <6 degrees. The results show that proposed system could be an option as an affordable-democratic solution.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Extracting data from Zhu, 2019 #5 daily life activities is important in biomechanical applications to define exact boundary conditions for the intended use-based applications. Although optoelectronic camera-marker based systems are used as gold standard tools for medical applications, due to line-of-sight problem, there is a need for wearable, affordable motion capture (MOCAP) systems. We investigate the potential use of a wearable inertial measurement unit (IMU) based-wearable MOCAP system for biomechanical applications. The in vitro proof of concept is provided for the full lower body consisting of hip, knee, and ankle joints via controlled single-plane anatomical range of motion (ROM) simulations using an electrical motor, while collecting data simultaneously via opto-electronic markers and IMU sensors. On 15 healthy volunteers the flexion-extension, abduction-adduction, internal-external rotation (ROM) values of hip and, the flexion - extension ROM values of the knee and ankle joints are calculated for both systems. The Bland-Altman graphs showed promising agreement both for in vitro and in vivo experiments. The maximum Root Mean Square Errors (RMSE) between the systems in vitro was 3.4 degrees for hip and 5.9 degrees for knee flexion motion in vivo, respectively. The gait data of the volunteers were assessed between the heel strike and toe off events to investigate the limits of agreement, calculating the population averages and standard deviation for both systems over the gait cycle. The maximum difference was for the ankle joint <6 degrees. The results show that proposed system could be an option as an affordable-democratic solution. |
Mihcin, Senay; Ciklacandir, Samet TOWARDS INTEGRATION OF THE FINITE ELEMENT MODELING TECHNIQUE INTO BIOMEDICAL ENGINEERING EDUCATION Journal Article BIOMEDICAL ENGINEERING-APPLICATIONS BASIS COMMUNICATIONS, 34 (02), 2022. @article{WOS:000786971300005, title = {TOWARDS INTEGRATION OF THE FINITE ELEMENT MODELING TECHNIQUE INTO BIOMEDICAL ENGINEERING EDUCATION}, author = {Senay Mihcin and Samet Ciklacandir}, doi = {10.4015/S101623722150054X}, year = {2022}, date = {2022-04-01}, journal = {BIOMEDICAL ENGINEERING-APPLICATIONS BASIS COMMUNICATIONS}, volume = {34}, number = {02}, abstract = {Biomedical engineering (BME) is a multidisciplinary field, resulting in a heavy course load from different fields. We hypothesize that, the engineering curriculum be tailored according to the requirements of the BME profession. In this study, we focus on the teaching of the finite element modeling (FEM) technique by redesigning the course to address the needs of the BME profession by some custom-made changes to meet the unmet. needs. After the completion of the course, evaluation methods of the students were analyzed and detailed over a survey providing feedback from the students. The surveys were related to the teaching the theory of FEM, the laboratory sessions, and the project sessions. The survey results were evaluated using statistical methods. The Pearson correlation coefficient showed a linear agreement between theoretical and practical sessions indicating efficient blending of skills because of the custom-made changes. The survey analysis showed that the students were in favour of the changes, allowing them to be more resourceful and confident with their skills. The positive results indicate a positive attitude among the students towards their profession. As the course design addresses the needs of the profession allowing students to fit in better, the students might, follow their own profession after graduation. A wider follow-up study might be planned next to compare the results between who received tailor-designed courses and those who did not.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Biomedical engineering (BME) is a multidisciplinary field, resulting in a heavy course load from different fields. We hypothesize that, the engineering curriculum be tailored according to the requirements of the BME profession. In this study, we focus on the teaching of the finite element modeling (FEM) technique by redesigning the course to address the needs of the BME profession by some custom-made changes to meet the unmet. needs. After the completion of the course, evaluation methods of the students were analyzed and detailed over a survey providing feedback from the students. The surveys were related to the teaching the theory of FEM, the laboratory sessions, and the project sessions. The survey results were evaluated using statistical methods. The Pearson correlation coefficient showed a linear agreement between theoretical and practical sessions indicating efficient blending of skills because of the custom-made changes. The survey analysis showed that the students were in favour of the changes, allowing them to be more resourceful and confident with their skills. The positive results indicate a positive attitude among the students towards their profession. As the course design addresses the needs of the profession allowing students to fit in better, the students might, follow their own profession after graduation. A wider follow-up study might be planned next to compare the results between who received tailor-designed courses and those who did not. |
2021 |
Mihcin, Senay; Ciklacandir, Samet; Kocak, Mertcan; Tosun, Aliye Wearable Motion Capture System Evaluation for Biomechanical Studies for Hip Joints Journal Article JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, 143 (4), 2021. @article{WOS:000626080400016, title = {Wearable Motion Capture System Evaluation for Biomechanical Studies for Hip Joints}, author = {Senay Mihcin and Samet Ciklacandir and Mertcan Kocak and Aliye Tosun}, doi = {10.1115/1.4049199}, year = {2021}, date = {2021-04-01}, journal = {JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME}, volume = {143}, number = {4}, abstract = {Human motion capture (MOCAP) systems are vital while determining the loads occurring at the joints. Most of the clinical MOCAP systems are very costly, requiring investment and infrastructure. Therefore, alternative technologies are in demand. In this study, a novel markerless wearable MOCAP system was assessed for its compatibility with a biomechanical modeling software. To collect evidence, experiments were designed in two stages for quantifying the range of motion (ROM) of the hip joint, in vitro and in vivo. Three constrained single-plane motions-abduction/adduction, flexion/extension, and internal/external rotation movements of the active leg-were analyzed. The data were collected from 14 healthy volunteers, using the wearable system and a medical grade optoelectronic MOCAP system simultaneously and compared against. For the in vitro study, the root-mean-square error (RMSE) for the abduction/adduction motion of the hip joint was calculated as 0.11deg/0.30deg and 0.11deg/0.09deg, respectively, for the wearable and the opto-electronic system. The in vivo Bland-Altman plots showed that the two system data are comparable. The simulation software is found compatible to run the simulations in offline mode. The wearable system could be utilized in the field of biomechanics software for running the kinetic simulations. The results demonstrated that the wearable system could be an alternative in the field of biomechanics based on the evidence collected.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Human motion capture (MOCAP) systems are vital while determining the loads occurring at the joints. Most of the clinical MOCAP systems are very costly, requiring investment and infrastructure. Therefore, alternative technologies are in demand. In this study, a novel markerless wearable MOCAP system was assessed for its compatibility with a biomechanical modeling software. To collect evidence, experiments were designed in two stages for quantifying the range of motion (ROM) of the hip joint, in vitro and in vivo. Three constrained single-plane motions-abduction/adduction, flexion/extension, and internal/external rotation movements of the active leg-were analyzed. The data were collected from 14 healthy volunteers, using the wearable system and a medical grade optoelectronic MOCAP system simultaneously and compared against. For the in vitro study, the root-mean-square error (RMSE) for the abduction/adduction motion of the hip joint was calculated as 0.11deg/0.30deg and 0.11deg/0.09deg, respectively, for the wearable and the opto-electronic system. The in vivo Bland-Altman plots showed that the two system data are comparable. The simulation software is found compatible to run the simulations in offline mode. The wearable system could be utilized in the field of biomechanics software for running the kinetic simulations. The results demonstrated that the wearable system could be an alternative in the field of biomechanics based on the evidence collected. |
2017 |
Mihcin, Senay; Karakitsios, Ioannis; Le, Nhan; Strehlow, Jan; Demedts, Daniel; Schwenke, Michael; Haase, Sabrina; Preusser, Tobias; Melzer, Andreas Methodology on quantification of sonication duration for safe application of MR guided focused ultrasound for liver tumour ablation Journal Article COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE, 152 , pp. 125-130, 2017, ISSN: 0169-2607. @article{ISI:000413258300013, title = {Methodology on quantification of sonication duration for safe application of MR guided focused ultrasound for liver tumour ablation}, author = {Senay Mihcin and Ioannis Karakitsios and Nhan Le and Jan Strehlow and Daniel Demedts and Michael Schwenke and Sabrina Haase and Tobias Preusser and Andreas Melzer}, doi = {10.1016/j.cmpb.2017.09.006}, issn = {0169-2607}, year = {2017}, date = {2017-12-01}, journal = {COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE}, volume = {152}, pages = {125-130}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Schwenke, Michael; Strehlow, Jan; Demedts, Daniel; Haase, Sabrina; Romero, Diego Barrios; Rothluebbers, Sven; von Dresky, Caroline; Zidowitz, Stephan; Georgii, Joachim; Mihcin, Senay; Bezzi, Mario; Tanner, Christine; Sat, Giora; Levy, Yoav; Jenne, Juergen; Guenther, Matthias; Melzer, Andreas; Preusser, Tobias A focused ultrasound treatment system for moving targets (part I): generic system design and in-silico first-stage evaluation Journal Article JOURNAL OF THERAPEUTIC ULTRASOUND, 5 , pp. 1-14, 2017, ISSN: 2050-5736. @article{ISI:000406663900001, title = {A focused ultrasound treatment system for moving targets (part I): generic system design and in-silico first-stage evaluation}, author = {Michael Schwenke and Jan Strehlow and Daniel Demedts and Sabrina Haase and Diego Barrios Romero and Sven Rothluebbers and Caroline von Dresky and Stephan Zidowitz and Joachim Georgii and Senay Mihcin and Mario Bezzi and Christine Tanner and Giora Sat and Yoav Levy and Juergen Jenne and Matthias Guenther and Andreas Melzer and Tobias Preusser}, doi = {10.1186/s40349-017-0098-7}, issn = {2050-5736}, year = {2017}, date = {2017-07-01}, journal = {JOURNAL OF THERAPEUTIC ULTRASOUND}, volume = {5}, pages = {1-14}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Karakitsios, Ioannis; Joy, Joyce; Mihcin, Senay; Melzer, Andreas Acoustic characterization of Thiel liver for magnetic resonance-guided focused ultrasound treatment Journal Article MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES, 26 (2), pp. 92-96, 2017, ISSN: 1364-5706. @article{ISI:000398127600005, title = {Acoustic characterization of Thiel liver for magnetic resonance-guided focused ultrasound treatment}, author = {Ioannis Karakitsios and Joyce Joy and Senay Mihcin and Andreas Melzer}, doi = {10.1080/13645706.2016.1253589}, issn = {1364-5706}, year = {2017}, date = {2017-01-01}, journal = {MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES}, volume = {26}, number = {2}, pages = {92-96}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2016 |
Mihcin, Senay Spinal curvature for the assessment of spinal stability Journal Article INTERNATIONAL JOURNAL OF BIOMEDICAL ENGINEERING AND TECHNOLOGY, 20 (3), pp. 226-242, 2016, ISSN: 1752-6418. @article{ISI:000384710300003, title = {Spinal curvature for the assessment of spinal stability}, author = {Senay Mihcin}, doi = {10.1504/IJBET.2016.075425}, issn = {1752-6418}, year = {2016}, date = {2016-01-01}, journal = {INTERNATIONAL JOURNAL OF BIOMEDICAL ENGINEERING AND TECHNOLOGY}, volume = {20}, number = {3}, pages = {226-242}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Karakitsios, Ioannis; Mihcin, Senay; Saliev, Timur; Melzer, Andreas Feasibility study of pre-clinical Thiel embalmed human cadaver for MR-guided focused ultrasound of the spine Journal Article MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES, 25 (3), pp. 154-161, 2016, ISSN: 1364-5706. @article{ISI:000383343900006, title = {Feasibility study of pre-clinical Thiel embalmed human cadaver for MR-guided focused ultrasound of the spine}, author = {Ioannis Karakitsios and Senay Mihcin and Timur Saliev and Andreas Melzer}, doi = {10.3109/13645706.2016.1150297}, issn = {1364-5706}, year = {2016}, date = {2016-01-01}, journal = {MINIMALLY INVASIVE THERAPY & ALLIED TECHNOLOGIES}, volume = {25}, number = {3}, pages = {154-161}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
0000 |
Alpkaya, Alican Tuncay; Mihcin, Senay The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement Journal Article TRIBOLOGY TRANSACTIONS, 0000. @article{WOS:000899732300001, title = {The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement}, author = {Alican Tuncay Alpkaya and Senay Mihcin}, doi = {10.1080/10402004.2022.2140727}, journal = {TRIBOLOGY TRANSACTIONS}, abstract = {Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 mm(3)/year for CoCr head and 21.0271 mm(3)/year for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 mm(3)/year for CoCr head and 1.8476 mm(3)/year for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopatextbackslashedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 mm(3)/year for CoCr head and 21.0271 mm(3)/year for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 mm(3)/year for CoCr head and 1.8476 mm(3)/year for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopatextbackslashedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants. |
Alpkaya, Alican Tuncay; Mihcin, Senay The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement Journal Article TRIBOLOGY TRANSACTIONS, 0000. @article{WOS:000899732300001b, title = {The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement}, author = {Alican Tuncay Alpkaya and Senay Mihcin}, doi = {10.1080/10402004.2022.2140727}, journal = {TRIBOLOGY TRANSACTIONS}, abstract = {Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 mm(3)/year for CoCr head and 21.0271 mm(3)/year for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 mm(3)/year for CoCr head and 1.8476 mm(3)/year for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopatextbackslashedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 mm(3)/year for CoCr head and 21.0271 mm(3)/year for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 mm(3)/year for CoCr head and 1.8476 mm(3)/year for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopatextbackslashedic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants. |
Prof. Dr. Serhan Özdemir
Educational Background
B.Sc. Dokuz Eylül University, Turkey, Mechanical Engineering, 1991
M.Sc. Illinois Institute of Technology, USA, Mechanical and Aerospace Engineering, 1996
Ph.D. University of Florida, USA, Mechanical Engineering, 1999
Research Interests
- Machine Health and Diagnostics
- Intelligent Control
- Intelligent Modelling
- +90 232 750 6773
- +90 232 750 6701
- Mechanical Engineering Building (116)
Publications
2017 |
Kosun, Caglar; Ozdemir, Serhan Determining the complexity of multi-component conformal systems: A platoon-based approach Journal Article PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS, 471 , pp. 688-695, 2017, ISSN: 0378-4371. @article{ISI:000393733300064, title = {Determining the complexity of multi-component conformal systems: A platoon-based approach}, author = {Caglar Kosun and Serhan Ozdemir}, doi = {10.1016/j.physa.2016.12.027}, issn = {0378-4371}, year = {2017}, date = {2017-04-01}, journal = {PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS}, volume = {471}, pages = {688-695}, abstract = {Many systems in nature and engineering are composed of subsystems. These subsystems may be formed in a linear, planar or spatial array. A typical example of these formations is a chain of vehicles known as platoon formation in traffic flow. Platoon formation of vehicles is a linear or planar formation of vehicles where a certain and a constant headway, and sideway if applicable, is provided in between every and each one of them. It is argued in this paper that a well-automated platoon formation of vehicles is an extreme case of conformity. During this transformation from a many degrees of freedom formation to a solid object, Tsallis q value is computed to be ranging from one extreme case of q = 3 to the other where q = 1, when classified in terms of inverse temperatures of clearance fluctuations. At one-extreme of q = 3, one observes unbounded fluctuations in clearance fluctuations so that inverse temperature distributions approach a Dirac delta at the origin. At the other extreme of g = 1, fluctuations in clearance tend to zero asymptotically, where a solid structure of agents (vehicles) emerges. The transition from q = 3 to q = 1 is investigated through synthetic and experimental clearance fluctuations between the cars. The results show that during the transition from q = 3 to q = 1, the platoon loses its many degrees of freedom (dof) of motion until a solid single object emerges. Authors assert that the Tsallis q value of a platoon of vehicles is limited to 3 > q > 1. (C) 2016 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Many systems in nature and engineering are composed of subsystems. These subsystems may be formed in a linear, planar or spatial array. A typical example of these formations is a chain of vehicles known as platoon formation in traffic flow. Platoon formation of vehicles is a linear or planar formation of vehicles where a certain and a constant headway, and sideway if applicable, is provided in between every and each one of them. It is argued in this paper that a well-automated platoon formation of vehicles is an extreme case of conformity. During this transformation from a many degrees of freedom formation to a solid object, Tsallis q value is computed to be ranging from one extreme case of q = 3 to the other where q = 1, when classified in terms of inverse temperatures of clearance fluctuations. At one-extreme of q = 3, one observes unbounded fluctuations in clearance fluctuations so that inverse temperature distributions approach a Dirac delta at the origin. At the other extreme of g = 1, fluctuations in clearance tend to zero asymptotically, where a solid structure of agents (vehicles) emerges. The transition from q = 3 to q = 1 is investigated through synthetic and experimental clearance fluctuations between the cars. The results show that during the transition from q = 3 to q = 1, the platoon loses its many degrees of freedom (dof) of motion until a solid single object emerges. Authors assert that the Tsallis q value of a platoon of vehicles is limited to 3 > q > 1. (C) 2016 Elsevier B.V. All rights reserved. |
Kosun, Caglar; Ozdemir, Serhan An entropy-based analysis of lane changing behavior: An interactive approach Journal Article TRAFFIC INJURY PREVENTION, 18 (4), pp. 441-447, 2017, ISSN: 1538-9588. @article{ISI:000399359600018, title = {An entropy-based analysis of lane changing behavior: An interactive approach}, author = {Caglar Kosun and Serhan Ozdemir}, doi = {10.1080/15389588.2016.1204446}, issn = {1538-9588}, year = {2017}, date = {2017-01-01}, journal = {TRAFFIC INJURY PREVENTION}, volume = {18}, number = {4}, pages = {441-447}, abstract = {Objectives: As a novelty, this article proposes the nonadditive entropy framework for the description of driver behaviors during lane changing. The authors also state that this entropy framework governs the lane changing behavior in traffic flow in accordance with the long-range vehicular interactions and traffic safety.Methods: The nonadditive entropy framework is the new generalized theory of thermostatistical mechanics. Vehicular interactions during lane changing are considered within this framework. The interactive approach for the lane changing behavior of the drivers is presented in the traffic flow scenarios presented in the article. According to the traffic flow scenarios, 4 categories of traffic flow and driver behaviors are obtained. Through the scenarios, comparative analyses of nonadditive and additive entropy domains are also provided.Results: Two quadrants of the categories belong to the nonadditive entropy; the rest are involved in the additive entropy domain. Driving behaviors are extracted and the scenarios depict that nonadditivity matches safe driving well, whereas additivity corresponds to unsafe driving. Furthermore, the cooperative traffic system is considered in nonadditivity where the long-range interactions are present. However, the uncooperative traffic system falls into the additivity domain. The analyses also state that there would be possible traffic flow transitions among the quadrants. This article shows that lane changing behavior could be generalized as nonadditive, with additivity as a special case, based on the given traffic conditions.Conclusions: The nearest and close neighbor models are well within the conventional additive entropy framework. In this article, both the long-range vehicular interactions and safe driving behavior in traffic are handled in the nonadditive entropy domain. It is also inferred that the Tsallis entropy region would correspond to mandatory lane changing behavior, whereas additive and either the extensive or nonextensive entropy region would match discretionary lane changing behavior. This article states that driver behaviors would be in the nonadditive entropy domain to provide a safe traffic stream and hence with vehicle accident prevention in mind.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objectives: As a novelty, this article proposes the nonadditive entropy framework for the description of driver behaviors during lane changing. The authors also state that this entropy framework governs the lane changing behavior in traffic flow in accordance with the long-range vehicular interactions and traffic safety.Methods: The nonadditive entropy framework is the new generalized theory of thermostatistical mechanics. Vehicular interactions during lane changing are considered within this framework. The interactive approach for the lane changing behavior of the drivers is presented in the traffic flow scenarios presented in the article. According to the traffic flow scenarios, 4 categories of traffic flow and driver behaviors are obtained. Through the scenarios, comparative analyses of nonadditive and additive entropy domains are also provided.Results: Two quadrants of the categories belong to the nonadditive entropy; the rest are involved in the additive entropy domain. Driving behaviors are extracted and the scenarios depict that nonadditivity matches safe driving well, whereas additivity corresponds to unsafe driving. Furthermore, the cooperative traffic system is considered in nonadditivity where the long-range interactions are present. However, the uncooperative traffic system falls into the additivity domain. The analyses also state that there would be possible traffic flow transitions among the quadrants. This article shows that lane changing behavior could be generalized as nonadditive, with additivity as a special case, based on the given traffic conditions.Conclusions: The nearest and close neighbor models are well within the conventional additive entropy framework. In this article, both the long-range vehicular interactions and safe driving behavior in traffic are handled in the nonadditive entropy domain. It is also inferred that the Tsallis entropy region would correspond to mandatory lane changing behavior, whereas additive and either the extensive or nonextensive entropy region would match discretionary lane changing behavior. This article states that driver behaviors would be in the nonadditive entropy domain to provide a safe traffic stream and hence with vehicle accident prevention in mind. |
2016 |
Kosun, Caglar; Ozdemir, Serhan A superstatistical model of vehicular traffic flow Journal Article PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS, 444 , pp. 466-475, 2016, ISSN: 0378-4371. @article{ISI:000366785900043, title = {A superstatistical model of vehicular traffic flow}, author = {Caglar Kosun and Serhan Ozdemir}, doi = {10.1016/j.physa.2015.10.042}, issn = {0378-4371}, year = {2016}, date = {2016-02-01}, journal = {PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS}, volume = {444}, pages = {466-475}, abstract = {In the analysis of vehicular traffic flow, a myriad of techniques have been implemented. In this study, superstatistics is used in modeling the traffic flow on a highway segment. Traffic variables such as vehicular speeds, volume, and headway were collected for three days. For the superstatistical approach, at least two distinct time scales must exist, so that a superposition of nonequilibrium systems assumption could hold. When the slow dynamics of the vehicle speeds exhibit a Gaussian distribution in between the fluctuations of the system at large, one speaks of a relaxation to a local equilibrium. These Gaussian distributions are found with corresponding standard deviations 1/root beta. This translates into a series of fluctuating beta values, hence the statistics of statistics, superstatistics. The traffic flow model has generated an inverse temperature parameter (beta) distribution as well as the speed distribution. This beta distribution has shown that the fluctuations in beta are distributed with respect to a chi-square distribution. It must be mentioned that two distinct Tsallis q values are specified: one is time-dependent and the other is independent. A ramification of these q values is that the highway segment and the traffic flow generate separate characteristics. This highway segment in question is not only nonadditive in nature, but a nonequilibrium driven system, with frequent relaxations to a Gaussian. (C) 2015 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the analysis of vehicular traffic flow, a myriad of techniques have been implemented. In this study, superstatistics is used in modeling the traffic flow on a highway segment. Traffic variables such as vehicular speeds, volume, and headway were collected for three days. For the superstatistical approach, at least two distinct time scales must exist, so that a superposition of nonequilibrium systems assumption could hold. When the slow dynamics of the vehicle speeds exhibit a Gaussian distribution in between the fluctuations of the system at large, one speaks of a relaxation to a local equilibrium. These Gaussian distributions are found with corresponding standard deviations 1/root beta. This translates into a series of fluctuating beta values, hence the statistics of statistics, superstatistics. The traffic flow model has generated an inverse temperature parameter (beta) distribution as well as the speed distribution. This beta distribution has shown that the fluctuations in beta are distributed with respect to a chi-square distribution. It must be mentioned that two distinct Tsallis q values are specified: one is time-dependent and the other is independent. A ramification of these q values is that the highway segment and the traffic flow generate separate characteristics. This highway segment in question is not only nonadditive in nature, but a nonequilibrium driven system, with frequent relaxations to a Gaussian. (C) 2015 Elsevier B.V. All rights reserved. |
2015 |
Kosun, Caglar; Celik, Huseyin Murat; Ozdemir, Serhan AN ANALYSIS OF VEHICULAR TRAFFIC FLOW USING LANGEVIN EQUATION Journal Article PROMET-TRAFFIC & TRANSPORTATION, 27 (4), pp. 317-324, 2015, ISSN: 0353-5320. @article{ISI:000361265300005, title = {AN ANALYSIS OF VEHICULAR TRAFFIC FLOW USING LANGEVIN EQUATION}, author = {Caglar Kosun and Huseyin Murat Celik and Serhan Ozdemir}, doi = {10.7307/ptt.v27i4.1613}, issn = {0353-5320}, year = {2015}, date = {2015-01-01}, journal = {PROMET-TRAFFIC & TRANSPORTATION}, volume = {27}, number = {4}, pages = {317-324}, abstract = {Traffic flow data are stochastic in nature, and an abundance of literature exists thereof. One way to express stochastic data is the Langevin equation. Langevin equation consists of two parts. The first part is known as the deterministic drift term, the other as the stochastic diffusion term. Langevin equation does not only help derive the deterministic and random terms of the selected portion of the city of Istanbul traffic empirically, but also sheds light on the underlying dynamics of the flow. Drift diagrams have shown that slow lane tends to get congested faster when vehicle speeds attain a value of 25 km/h, and it is 20 km/h for the fast lane. Three or four distinct regimes may be discriminated again from the drift diagrams; congested, intermediate, and free-flow regimes. At places, even the intermediate regime may be divided in two, often with readiness to congestion. This has revealed the fact that for the selected portion of the highway, there are two main states of flow, namely, congestion and free-flow, with an intermediate state where the noise-driven traffic flow forces the flow into either of the distinct regimes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Traffic flow data are stochastic in nature, and an abundance of literature exists thereof. One way to express stochastic data is the Langevin equation. Langevin equation consists of two parts. The first part is known as the deterministic drift term, the other as the stochastic diffusion term. Langevin equation does not only help derive the deterministic and random terms of the selected portion of the city of Istanbul traffic empirically, but also sheds light on the underlying dynamics of the flow. Drift diagrams have shown that slow lane tends to get congested faster when vehicle speeds attain a value of 25 km/h, and it is 20 km/h for the fast lane. Three or four distinct regimes may be discriminated again from the drift diagrams; congested, intermediate, and free-flow regimes. At places, even the intermediate regime may be divided in two, often with readiness to congestion. This has revealed the fact that for the selected portion of the highway, there are two main states of flow, namely, congestion and free-flow, with an intermediate state where the noise-driven traffic flow forces the flow into either of the distinct regimes. |
2011 |
Gezgin, Erkin; Ozdemir, Serhan Classification of manipulators of the same origin by virtue of compactness and complexity Journal Article MECHANISM AND MACHINE THEORY, 46 (10), pp. 1425-1433, 2011, ISSN: 0094-114X. @article{ISI:000293062700007, title = {Classification of manipulators of the same origin by virtue of compactness and complexity}, author = {Erkin Gezgin and Serhan Ozdemir}, doi = {10.1016/j.mechmachtheory.2011.05.009}, issn = {0094-114X}, year = {2011}, date = {2011-10-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {46}, number = {10}, pages = {1425-1433}, abstract = {This work deals with a classification method that employs concepts such as complexity and compactness. The idea is to classify manipulators, or any other mechanism for that matter, of the same origin, based on the geometry of the joints, the tasks performed by the joints, the efficiency and the manufacturing cost to generate the specified efficiency. It is known that successive units on a single branch create individual uncertainties that affect the eventual quality of the performed operation [1]. An entropic expression quantifies this uncertainty in terms of the number of links and the unit effectiveness. The concepts of compactness and complexity have been formulated, and these concepts are explained through serial and parallel manipulators with varying parameters. Eventually, a cost function is created which is a function of complexity, uncertainty and the manufacturing cost. A worked example on M = 6 Stewart-Gough platform is given how this cost function could be taken advantage of when deciding an initial manipulator. A genetic algorithm is used for the optimization of the cost function, where the results are tabulated. (C) 2011 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This work deals with a classification method that employs concepts such as complexity and compactness. The idea is to classify manipulators, or any other mechanism for that matter, of the same origin, based on the geometry of the joints, the tasks performed by the joints, the efficiency and the manufacturing cost to generate the specified efficiency. It is known that successive units on a single branch create individual uncertainties that affect the eventual quality of the performed operation [1]. An entropic expression quantifies this uncertainty in terms of the number of links and the unit effectiveness. The concepts of compactness and complexity have been formulated, and these concepts are explained through serial and parallel manipulators with varying parameters. Eventually, a cost function is created which is a function of complexity, uncertainty and the manufacturing cost. A worked example on M = 6 Stewart-Gough platform is given how this cost function could be taken advantage of when deciding an initial manipulator. A genetic algorithm is used for the optimization of the cost function, where the results are tabulated. (C) 2011 Elsevier Ltd. All rights reserved. |
Coskun, Anil; Sevil, Hakki Erhan; Ozdemir, Serhan Cost effective localization in distributed sensory networks Journal Article ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENCE, 24 (2), pp. 232-237, 2011, ISSN: 0952-1976. @article{ISI:000287066800003, title = {Cost effective localization in distributed sensory networks}, author = {Anil Coskun and Hakki Erhan Sevil and Serhan Ozdemir}, doi = {10.1016/j.engappai.2010.10.006}, issn = {0952-1976}, year = {2011}, date = {2011-03-01}, journal = {ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENCE}, volume = {24}, number = {2}, pages = {232-237}, abstract = {The most important mechanism to occur in biological distributed sensory networks (DSNs) is called lateral inhibition, (LI). LI relies on one simple principle. Each sensor strives to suppress its neighbors in proportion to its own excitation. In this study, LI mechanism is exploited to localize the unknown position of a light source that illuminated the photosensitive sensory network containing high and low quality sensors. Each photosensitive sensor was then calibrated to accurately read the distance to the light source. A series of experiments were conducted employing both quality sensors. Low quality array was allowed to take advantage of LI, whereas the high quality one was not. Results showed that the lateral inhibition mechanism increased the sensitivity of inferior quality sensors, giving the ability to make the localization as sensitive as high quality sensors do. This suggests that the networks with multitude of sensors could be made cost-effective, were these sensory networks equipped with LI. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The most important mechanism to occur in biological distributed sensory networks (DSNs) is called lateral inhibition, (LI). LI relies on one simple principle. Each sensor strives to suppress its neighbors in proportion to its own excitation. In this study, LI mechanism is exploited to localize the unknown position of a light source that illuminated the photosensitive sensory network containing high and low quality sensors. Each photosensitive sensor was then calibrated to accurately read the distance to the light source. A series of experiments were conducted employing both quality sensors. Low quality array was allowed to take advantage of LI, whereas the high quality one was not. Results showed that the lateral inhibition mechanism increased the sensitivity of inferior quality sensors, giving the ability to make the localization as sensitive as high quality sensors do. This suggests that the networks with multitude of sensors could be made cost-effective, were these sensory networks equipped with LI. (C) 2010 Elsevier Ltd. All rights reserved. |
Sevil, Hakki Erhan; Ozdemir, Serhan Prediction of microdrill breakage using rough sets Journal Article AI EDAM-ARTIFICIAL INTELLIGENCE FOR ENGINEERING DESIGN ANALYSIS AND MANUFACTURING, 25 (1), pp. 15-23, 2011, ISSN: 0890-0604. @article{ISI:000287388000002, title = {Prediction of microdrill breakage using rough sets}, author = {Hakki Erhan Sevil and Serhan Ozdemir}, doi = {10.1017/S0890060410000144}, issn = {0890-0604}, year = {2011}, date = {2011-02-01}, journal = {AI EDAM-ARTIFICIAL INTELLIGENCE FOR ENGINEERING DESIGN ANALYSIS AND MANUFACTURING}, volume = {25}, number = {1}, pages = {15-23}, abstract = {This study attempts to correlate the nonlinear invariants' with the changing conditions of a drilling process through a series of condition monitoring experiments on small diameter (1 mm) drill bits. Run-to-failure tests are performed on these drill bits, and vibration data are consecutively gathered at equal time intervals. Nonlinear invariants, such as the Kolmogorov entropy and correlation dimension, and statistical parameters are calculated based on the corresponding conditions of the drill bits. By intervariations of these values between two successive measurements, a drop rise table is created. Any variation that is within a certain threshold (+/-20% of the measurements in this case) is assumed to be constant. Any fluctuation above or below is assumed to be either a rise or a drop. The reduct and conflict tables then help eliminate incongruous and redundant data by the use of rough sets (RSs). Inconsistent data, which by definition is the boundary region, are classified through certainty and coverage factors. By handling inconsistencies and redundancies, 11 rules are extracted from 39 experiments, representing the underlying rules. Then 22 new experiments are used to check the validity of the rule space. The RS decision frame performs best at predicting no failure cases. It is believed that RSs are superior in dealing with real-life data over fuzzy set logic in that actual measured data are never as consistent as here and may dominate the monitoring of the manufacturing processes as it becomes more widespread.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study attempts to correlate the nonlinear invariants' with the changing conditions of a drilling process through a series of condition monitoring experiments on small diameter (1 mm) drill bits. Run-to-failure tests are performed on these drill bits, and vibration data are consecutively gathered at equal time intervals. Nonlinear invariants, such as the Kolmogorov entropy and correlation dimension, and statistical parameters are calculated based on the corresponding conditions of the drill bits. By intervariations of these values between two successive measurements, a drop rise table is created. Any variation that is within a certain threshold (+/-20% of the measurements in this case) is assumed to be constant. Any fluctuation above or below is assumed to be either a rise or a drop. The reduct and conflict tables then help eliminate incongruous and redundant data by the use of rough sets (RSs). Inconsistent data, which by definition is the boundary region, are classified through certainty and coverage factors. By handling inconsistencies and redundancies, 11 rules are extracted from 39 experiments, representing the underlying rules. Then 22 new experiments are used to check the validity of the rule space. The RS decision frame performs best at predicting no failure cases. It is believed that RSs are superior in dealing with real-life data over fuzzy set logic in that actual measured data are never as consistent as here and may dominate the monitoring of the manufacturing processes as it becomes more widespread. |
2008 |
Ozdemir, Serhan Power transmission entropy Journal Article International Journal of Heavy Vehicle Systems, 15 (1), pp. 82–88, 2008. @article{ozdemir2008power, title = {Power transmission entropy}, author = {Serhan Ozdemir}, year = {2008}, date = {2008-01-01}, journal = {International Journal of Heavy Vehicle Systems}, volume = {15}, number = {1}, pages = {82--88}, publisher = {Inderscience Publishers}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2007 |
Ozdemir, Serhan Measures of uncertainty in power split systems Journal Article MECHANISM AND MACHINE THEORY, 42 (2), pp. 159-167, 2007, ISSN: 0094-114X. @article{ISI:000243623800003, title = {Measures of uncertainty in power split systems}, author = {Serhan Ozdemir}, doi = {10.1016/j.mechmachtheory.2006.04.008}, issn = {0094-114X}, year = {2007}, date = {2007-02-01}, journal = {MECHANISM AND MACHINE THEORY}, volume = {42}, number = {2}, pages = {159-167}, abstract = {This paper discusses the overlooked uncertainty inherent in every transmission. The uncertainty aspect has been often, for the sake of clarity, ignored. Instead, mechanical transmissions have been characterized traditionally by their transmission efficacies. It is known that transmission localities are sources of power loss, depending on many factors, hence sources of uncertainty. Thus each transmission of power should not only be designated by a constant of efficiency but also by an expression of uncertainty, reflecting the probability of transmission. Furthermore, Shannon's and Renyi's expressions of entropy have been used to quantify this so-called transmission uncertainty. The entropy of a transmitting unit is given in these two forms and then compared. Practical formulations for flow optimization are given. (C) 2006 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper discusses the overlooked uncertainty inherent in every transmission. The uncertainty aspect has been often, for the sake of clarity, ignored. Instead, mechanical transmissions have been characterized traditionally by their transmission efficacies. It is known that transmission localities are sources of power loss, depending on many factors, hence sources of uncertainty. Thus each transmission of power should not only be designated by a constant of efficiency but also by an expression of uncertainty, reflecting the probability of transmission. Furthermore, Shannon's and Renyi's expressions of entropy have been used to quantify this so-called transmission uncertainty. The entropy of a transmitting unit is given in these two forms and then compared. Practical formulations for flow optimization are given. (C) 2006 Elsevier Ltd. All rights reserved. |
Assoc. Prof. Dr. Ünver Özkol
Educational Background
B.Sc. İstanbul Technical University, Turkey, Mechanical Engineering, 1991
M.Sc. Illinois Institute of Technology, USA, Mechanical and Aerospace Engineering, 1996
Ph.D. Illinois Institute of Technology, USA, Mechanical and Aerospace Engineering, 2002
Research Interests
- Turbulent and Separated Flows in machinery
- Experimental fluid mechanics (Optical techniques, thermal anemometry and flow visualization)
- Heat transfer enhancement, Cooling of Electronic Equipment with single and multiphase heat transfer
- +90 232 750 6770
- +90 232 750 6701
- Mechanical Engineering Building (113)
Publications
2024 |
Ulu, Anılcan; Yildiz, Güray; Özkol, Ünver; Rodriguez, Alvaro Diez Experimental investigation of spray characteristics of ethyl esters in a constant volume chamber Journal Article 14 (2), pp. 2643 – 2660, 2024. @article{Ulu20242643, title = {Experimental investigation of spray characteristics of ethyl esters in a constant volume chamber}, author = {Anılcan Ulu and Güray Yildiz and Ünver Özkol and Alvaro Diez Rodriguez}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125134221&doi=10.1007%2fs13399-022-02476-3&partnerID=40&md5=f56d167f075688de07dc30653fa40c64}, doi = {10.1007/s13399-022-02476-3}, year = {2024}, date = {2024-01-01}, volume = {14}, number = {2}, pages = {2643 – 2660}, abstract = {Abstract: Biodiesels are mainly produced via the utilization of methanol in transesterification, which is the widespread biodiesel production process. The majority of this methanol is currently obtained from fossil resources, i.e. coal and natural gas. However, in contrast with methanol, biomass-based ethanol can also be used to produce biodiesels; this could allow the production line to become fully renewable. This study aimed to investigate the spray characteristics of various ethyl ester type biodiesels derived from sunflower and corn oils in comparison to methyl esters based on the same feedstocks and reference petroleum-based diesel. Spray penetration length (SPL) and spray cone angle (SCA) were experimentally evaluated in a constant volume chamber allowing optical access, under chamber pressures of 0, 5, 10 and 15 bar and injection pressures of 600 and 800 bar. Sauter mean diameter (SMD) values were estimated by using an analytical correlation. Consequently, ethyl esters performed longer SPL (2.8–20%) and narrower SCA (5.1–19%) than diesel under ambient pressures of 5 and 10 bar. Although the SMD values of ethyl esters were 48% higher than diesel on average, their macroscopic spray characteristics were very similar to those of diesel under 15 bar chamber pressure. Moreover, ethyl esters were found to be very similar to methyl esters in terms of spray characteristics. The differences in SPL, SCA and SMD values for both types of biodiesels were lower than 4%. When considering the uncertainty (± 0.84%) and repeatability (±5%) ratios, the difference between the spray characteristics of methyl and ethyl esters was not major. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Abstract: Biodiesels are mainly produced via the utilization of methanol in transesterification, which is the widespread biodiesel production process. The majority of this methanol is currently obtained from fossil resources, i.e. coal and natural gas. However, in contrast with methanol, biomass-based ethanol can also be used to produce biodiesels; this could allow the production line to become fully renewable. This study aimed to investigate the spray characteristics of various ethyl ester type biodiesels derived from sunflower and corn oils in comparison to methyl esters based on the same feedstocks and reference petroleum-based diesel. Spray penetration length (SPL) and spray cone angle (SCA) were experimentally evaluated in a constant volume chamber allowing optical access, under chamber pressures of 0, 5, 10 and 15 bar and injection pressures of 600 and 800 bar. Sauter mean diameter (SMD) values were estimated by using an analytical correlation. Consequently, ethyl esters performed longer SPL (2.8–20%) and narrower SCA (5.1–19%) than diesel under ambient pressures of 5 and 10 bar. Although the SMD values of ethyl esters were 48% higher than diesel on average, their macroscopic spray characteristics were very similar to those of diesel under 15 bar chamber pressure. Moreover, ethyl esters were found to be very similar to methyl esters in terms of spray characteristics. The differences in SPL, SCA and SMD values for both types of biodiesels were lower than 4%. When considering the uncertainty (± 0.84%) and repeatability (±5%) ratios, the difference between the spray characteristics of methyl and ethyl esters was not major. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature. |
2019 |
Acarer, Sercan; Özkol, Ünver Off-Design Analysis of Transonic Bypass Fan Systems Using Streamline Curvature Through-Flow Method Journal Article International Journal of Turbo and Jet Engines, 36 (2), pp. 137 – 146, 2019, (All Open Access, Green Open Access). @article{Acarer2019137, title = {Off-Design Analysis of Transonic Bypass Fan Systems Using Streamline Curvature Through-Flow Method}, author = {Sercan Acarer and Ünver Özkol}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046815136&doi=10.1515%2ftjj-2016-0083&partnerID=40&md5=3b24de44dd45ff48c0814f96a18258cc}, doi = {10.1515/tjj-2016-0083}, year = {2019}, date = {2019-01-01}, journal = {International Journal of Turbo and Jet Engines}, volume = {36}, number = {2}, pages = {137 – 146}, abstract = {The two-dimensional streamline curvature through-flow modeling of turbomachinery is still a key element for turbomachinery preliminary analysis. Basically, axisymmetric swirling flow field is solved numerically. The effects of blades are imposed as sources of swirl, work input/output and entropy generation. Although the topic is studied vastly in the literature for compressors and turbines, combined modeling of the transonic fan and the downstream splitter of turbofan engine configuration, to the authors' best knowledge, is limited. In a prior study, the authors presented a new method for bypass fan modeling for inverse design calculations. Moreover, new set of practical empirical correlations are calibrated and validated. This paper is an extension of this study to rapid off-design analysis of transonic by-pass fan systems. The methodology is validated by two test cases: NASA 2-stage fan and GE-NASA bypass fan case. The proposed methodology is a simple extension for streamline curvature method and can be applied to existing compressor methodologies with minimum numerical effort. © 2019 Walter de Gruyter GmbH, Berlin/Boston.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } The two-dimensional streamline curvature through-flow modeling of turbomachinery is still a key element for turbomachinery preliminary analysis. Basically, axisymmetric swirling flow field is solved numerically. The effects of blades are imposed as sources of swirl, work input/output and entropy generation. Although the topic is studied vastly in the literature for compressors and turbines, combined modeling of the transonic fan and the downstream splitter of turbofan engine configuration, to the authors' best knowledge, is limited. In a prior study, the authors presented a new method for bypass fan modeling for inverse design calculations. Moreover, new set of practical empirical correlations are calibrated and validated. This paper is an extension of this study to rapid off-design analysis of transonic by-pass fan systems. The methodology is validated by two test cases: NASA 2-stage fan and GE-NASA bypass fan case. The proposed methodology is a simple extension for streamline curvature method and can be applied to existing compressor methodologies with minimum numerical effort. © 2019 Walter de Gruyter GmbH, Berlin/Boston. |
Celik, Hasan; Mobedi, Moghtada; Nakayama, Akira; Ozkol, Unver Journal of Porous Media, 22 (5), pp. 511 – 529, 2019, (All Open Access, Green Open Access). @article{Celik2019511, title = {A study on numerical determination of permeability and inertia coefficient of aluminum foam using X-ray microtomography technique: Focus on inspection methods for reliability (permeability and inertia coefficient by tomography)}, author = {Hasan Celik and Moghtada Mobedi and Akira Nakayama and Unver Ozkol}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065613946&doi=10.1615%2fJPorMedia.2019028887&partnerID=40&md5=cc89991bf14176783bc2c187db3358c8}, doi = {10.1615/JPorMedia.2019028887}, year = {2019}, date = {2019-01-01}, journal = {Journal of Porous Media}, volume = {22}, number = {5}, pages = {511 – 529}, abstract = {The volume-averaged (i.e., macroscopic) transport properties such as permeability and inertia coefficient of two aluminum foams with 10 and 20 pores per inch (PPI) pore density are found using microtomography images. It is shown that a comparison between the numerical values and the experimental results may not be sufficient to prove the correctness of the obtained results. Hence, in addition to traditional validation methods such as grid independency and comparison with reported results in literature, further inspections such as (a) checking the development of flow, (b) inspection of Darcy and non-Darcy regions, (c) conservation of flow rate through the porous media, (d) sufficiency of number of voxels in the narrow throats, and (e) observation of transverse velocity gradients in pores for high and low Reynolds numbers can be performed to further validate the achieved results. These techniques have been discussed and explained in detail for the performed study. Moreover, the obtained permeability and inertia coefficient values are compared with 19 reported theoretical, numerical, and experimental studies. The maximum deviation between the present results and the reported studies for 10 PPI is below 25%, while for 20 PPI it is below 28%. © 2019 by Begell House, Inc.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } The volume-averaged (i.e., macroscopic) transport properties such as permeability and inertia coefficient of two aluminum foams with 10 and 20 pores per inch (PPI) pore density are found using microtomography images. It is shown that a comparison between the numerical values and the experimental results may not be sufficient to prove the correctness of the obtained results. Hence, in addition to traditional validation methods such as grid independency and comparison with reported results in literature, further inspections such as (a) checking the development of flow, (b) inspection of Darcy and non-Darcy regions, (c) conservation of flow rate through the porous media, (d) sufficiency of number of voxels in the narrow throats, and (e) observation of transverse velocity gradients in pores for high and low Reynolds numbers can be performed to further validate the achieved results. These techniques have been discussed and explained in detail for the performed study. Moreover, the obtained permeability and inertia coefficient values are compared with 19 reported theoretical, numerical, and experimental studies. The maximum deviation between the present results and the reported studies for 10 PPI is below 25%, while for 20 PPI it is below 28%. © 2019 by Begell House, Inc. |
2018 |
Kor, Orcun; Acarer, Sercan; Ozkol, Unver Aerodynamic optimization of through-flow design model of a high by-pass transonic aero-engine fan using genetic algorithm Journal Article PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY, 232 (3), pp. 211-224, 2018, ISSN: 0957-6509. @article{ISI:000435491500001, title = {Aerodynamic optimization of through-flow design model of a high by-pass transonic aero-engine fan using genetic algorithm}, author = {Orcun Kor and Sercan Acarer and Unver Ozkol}, doi = {10.1177/0957650917730466}, issn = {0957-6509}, year = {2018}, date = {2018-05-01}, journal = {PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY}, volume = {232}, number = {3}, pages = {211-224}, abstract = {This study deals with aerodynamic optimization of a high by-pass transonic aero-engine fan module in a through-flow inverse design model at cruise condition. To the authors' best knowledge, although the literature contains through-flow optimization of the simplified cases of compressors and turbines, an optimization study targeting the more elaborate case of combined transonic fan and splitter through-flow model is not considered in the literature. Such a through-flow optimization of a transonic fan, combined with bypass and core streams separated by an aerodynamically shaped flow splitter, possesses significant challenges to any optimizer, due to highly non-linear nature of the problem and the high number of constraints, including the fulfillment of the targeted bypass ratio. It is the aim of this study to consider this previously untouched area in detail and therefore present a more sophisticated and accurate optimization environment for actual bypass fan systems. An in-house optimization code using genetic algorithm is coupled with a previously developed in-house through-flow solver which is using a streamline curvature technique and a set of in-house calibrated empirical models for incidence, deviation, loss and blockage. As the through-flow models are the backbone of turbo-machinery design, and great majority of design decisions are taken in this phase, such a study is assessed to result in significant guidelines to the gas turbine community.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study deals with aerodynamic optimization of a high by-pass transonic aero-engine fan module in a through-flow inverse design model at cruise condition. To the authors' best knowledge, although the literature contains through-flow optimization of the simplified cases of compressors and turbines, an optimization study targeting the more elaborate case of combined transonic fan and splitter through-flow model is not considered in the literature. Such a through-flow optimization of a transonic fan, combined with bypass and core streams separated by an aerodynamically shaped flow splitter, possesses significant challenges to any optimizer, due to highly non-linear nature of the problem and the high number of constraints, including the fulfillment of the targeted bypass ratio. It is the aim of this study to consider this previously untouched area in detail and therefore present a more sophisticated and accurate optimization environment for actual bypass fan systems. An in-house optimization code using genetic algorithm is coupled with a previously developed in-house through-flow solver which is using a streamline curvature technique and a set of in-house calibrated empirical models for incidence, deviation, loss and blockage. As the through-flow models are the backbone of turbo-machinery design, and great majority of design decisions are taken in this phase, such a study is assessed to result in significant guidelines to the gas turbine community. |
Celik, Hasan; Mobedi, Moghtada; Nakayama, Akira; Ozkol, Unver Numerical Heat Transfer; Part A: Applications, 74 (7), pp. 1368 – 1386, 2018, (All Open Access, Green Open Access). @article{Celik20181368, title = {A numerical study on determination of volume averaged thermal transport properties of metal foam structures using X-ray microtomography technique}, author = {Hasan Celik and Moghtada Mobedi and Akira Nakayama and Unver Ozkol}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057255888&doi=10.1080%2f10407782.2018.1494936&partnerID=40&md5=48bd8293534537dec7583acb2bf5c66f}, doi = {10.1080/10407782.2018.1494936}, year = {2018}, date = {2018-01-01}, journal = {Numerical Heat Transfer; Part A: Applications}, volume = {74}, number = {7}, pages = {1368 – 1386}, abstract = {Volume averaged thermal transport properties of two metal foams with 10 and 20 PPI are obtained by using microtomography technique. The digital 3D structures of samples are generated in computer environment. The governing equations are solved for the entire domain and the volume averaged technique is used to determine interfacial heat transfer coefficient, longitudinal and transverse thermal dispersion conductivity. The study is performed for the pore scale Reynolds number from 100 to 600. The obtained results are within the ranges of the suggested correlations in literature. The present study supports the correlations suggested by Calmidi and Mahajan (2000) and Zhang et al. (2016). © 2018, © 2018 Taylor & Francis Group, LLC.}, note = {All Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Volume averaged thermal transport properties of two metal foams with 10 and 20 PPI are obtained by using microtomography technique. The digital 3D structures of samples are generated in computer environment. The governing equations are solved for the entire domain and the volume averaged technique is used to determine interfacial heat transfer coefficient, longitudinal and transverse thermal dispersion conductivity. The study is performed for the pore scale Reynolds number from 100 to 600. The obtained results are within the ranges of the suggested correlations in literature. The present study supports the correlations suggested by Calmidi and Mahajan (2000) and Zhang et al. (2016). © 2018, © 2018 Taylor & Francis Group, LLC. |
2017 |
Celik, Hasan; Mobedi, Moghtada; Manca, Oronzio; Ozkol, Unver A pore scale analysis for determination of interfacial convective heat transfer coefficient for thin periodic porousmedia undermixed convection Journal Article INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW, 27 (12), pp. 2775-2798, 2017, ISSN: 0961-5539. @article{ISI:000416431600006b, title = {A pore scale analysis for determination of interfacial convective heat transfer coefficient for thin periodic porousmedia undermixed convection}, author = {Hasan Celik and Moghtada Mobedi and Oronzio Manca and Unver Ozkol}, doi = {10.1108/HFF-01-2017-0036}, issn = {0961-5539}, year = {2017}, date = {2017-01-01}, journal = {INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW}, volume = {27}, number = {12}, pages = {2775-2798}, abstract = {Purpose - The purpose of this study is to determine interfacial convective heat transfer coefficient numerically, for a porous media consisting of square blocks in inline arrangement under mixed convection heat transfer. Design/methodology/approach - The continuity, momentum and energy equations are solved in dimensionless form for a representative elementary volume of porous media, numerically. The velocity and temperature fields for different values of porosity, Ri and Re numbers are obtained. The study is performed for the range of Ri number from 0.01 to 10, Re number from 100 to 500 and porosity value from 0.51 to 0.96. Based on the obtained results, the value of the interfacial convective heat transfer coefficient is calculated by using volume average method. Findings - It was found that at low porosities (such as 0.51), the interfacial Nusselt number does not considerably change with Ri and Re numbers. However, for porous media with high Ri number and porosity (such as 10 and 0.51, respectively), secondary flows occur in the middle of the channel between rods improving heat transfer between solid and fluid, considerably. It is shown that the available correlations of interfacial heat transfer coefficient suggested for forced convection can be used for mixed convection for the porous media with low porosity (such as 0.51) or for the flow with low Ri number (such as 0.01). Originality/value - To the best of the authors' knowledge, there is no study on determination of interfacial convective heat transfer coefficient for mixed convection in porous media in literature. The present study might be the first study providing an accurate idea on the range of this important parameter, which will be useful particularly for researchers who study on mixed convection heat transfer in porous media, macroscopically.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Purpose - The purpose of this study is to determine interfacial convective heat transfer coefficient numerically, for a porous media consisting of square blocks in inline arrangement under mixed convection heat transfer. Design/methodology/approach - The continuity, momentum and energy equations are solved in dimensionless form for a representative elementary volume of porous media, numerically. The velocity and temperature fields for different values of porosity, Ri and Re numbers are obtained. The study is performed for the range of Ri number from 0.01 to 10, Re number from 100 to 500 and porosity value from 0.51 to 0.96. Based on the obtained results, the value of the interfacial convective heat transfer coefficient is calculated by using volume average method. Findings - It was found that at low porosities (such as 0.51), the interfacial Nusselt number does not considerably change with Ri and Re numbers. However, for porous media with high Ri number and porosity (such as 10 and 0.51, respectively), secondary flows occur in the middle of the channel between rods improving heat transfer between solid and fluid, considerably. It is shown that the available correlations of interfacial heat transfer coefficient suggested for forced convection can be used for mixed convection for the porous media with low porosity (such as 0.51) or for the flow with low Ri number (such as 0.01). Originality/value - To the best of the authors' knowledge, there is no study on determination of interfacial convective heat transfer coefficient for mixed convection in porous media in literature. The present study might be the first study providing an accurate idea on the range of this important parameter, which will be useful particularly for researchers who study on mixed convection heat transfer in porous media, macroscopically. |
2014 |
Ozgumus, Turkuler; Mobedi, Moghtada; Ozkol, Unver DETERMINATION OF KOZENY CONSTANT BASED ON POROSITY AND PORE TO THROAT SIZE RATIO IN POROUS MEDIUM WITH RECTANGULAR RODS Journal Article ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS, 8 (2), pp. 308-318, 2014, ISSN: 1994-2060. @article{ISI:000337224100010, title = {DETERMINATION OF KOZENY CONSTANT BASED ON POROSITY AND PORE TO THROAT SIZE RATIO IN POROUS MEDIUM WITH RECTANGULAR RODS}, author = {Turkuler Ozgumus and Moghtada Mobedi and Unver Ozkol}, doi = {10.1080/19942060.2014.11015516}, issn = {1994-2060}, year = {2014}, date = {2014-06-01}, journal = {ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS}, volume = {8}, number = {2}, pages = {308-318}, abstract = {Kozeny-Carman permeability equation is an important relation for the determination of permeability in porous media. In this study, the permeabilities of porous media that contains rectangular rods are determined, numerically. The applicability of Kozeny-Carman equation for the periodic porous media is investigated and the effects of porosity and pore to throat size ratio on Kozeny constant are studied. The continuity and Navier-Stokes equations are solved to determine the velocity and pressure fields in the voids between the rods. Based on the obtained flow field, the permeability values for different porosities from 0.2 to 0.9 and pore to throat size ratio values from 1.63 to 7.46 are computed. Then Kozeny constants for different porous media with various porosity and pore to throat size ratios are obtained and a relationship between Kozeny constant, porosity and pore to throat size ratio is constructed. The study reveals that the pore to throat size ratio is an important geometrical parameter that should be taken into account for deriving a correlation for permeability. The suggestion of a fixed value for Kozeny constant makes the application of Kozeny-Carman permeability equation too narrow for a very specific porous medium. However, it is possible to apply the Kozeny-Carman permeability equation for wide ranges of porous media with different geometrical parameters (various porosity, hydraulic diameter, particle size and aspect ratio) if Kozeny constant is a function of two parameters as porosity and pore to throat size ratios.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Kozeny-Carman permeability equation is an important relation for the determination of permeability in porous media. In this study, the permeabilities of porous media that contains rectangular rods are determined, numerically. The applicability of Kozeny-Carman equation for the periodic porous media is investigated and the effects of porosity and pore to throat size ratio on Kozeny constant are studied. The continuity and Navier-Stokes equations are solved to determine the velocity and pressure fields in the voids between the rods. Based on the obtained flow field, the permeability values for different porosities from 0.2 to 0.9 and pore to throat size ratio values from 1.63 to 7.46 are computed. Then Kozeny constants for different porous media with various porosity and pore to throat size ratios are obtained and a relationship between Kozeny constant, porosity and pore to throat size ratio is constructed. The study reveals that the pore to throat size ratio is an important geometrical parameter that should be taken into account for deriving a correlation for permeability. The suggestion of a fixed value for Kozeny constant makes the application of Kozeny-Carman permeability equation too narrow for a very specific porous medium. However, it is possible to apply the Kozeny-Carman permeability equation for wide ranges of porous media with different geometrical parameters (various porosity, hydraulic diameter, particle size and aspect ratio) if Kozeny constant is a function of two parameters as porosity and pore to throat size ratios. |
2013 |
Ozgumus, Turkuler; Mobedi, Moghtada; Ozkol, Unver; Nakayama, Akira Thermal Dispersion in Porous Media-A Review on the Experimental Studies for Packed Beds Journal Article APPLIED MECHANICS REVIEWS, 65 (3), 2013, ISSN: 0003-6900. @article{ISI:000329612200001, title = {Thermal Dispersion in Porous Media-A Review on the Experimental Studies for Packed Beds}, author = {Turkuler Ozgumus and Moghtada Mobedi and Unver Ozkol and Akira Nakayama}, doi = {10.1115/1.4024351}, issn = {0003-6900}, year = {2013}, date = {2013-05-01}, journal = {APPLIED MECHANICS REVIEWS}, volume = {65}, number = {3}, abstract = {Thermal dispersion is an important topic in the convective heat transfer in porous media. In order to determine the heat transfer in a packed bed, the effective thermal conductivity including both stagnant and dispersion thermal conductivities should be known. Several theoretical and experimental studies have been performed on the determination of the effective thermal conductivity. The aim of this study is to review the experimental studies done on the determination of the effective thermal conductivity of the packed beds. In this study, firstly brief information on the definition of the thermal dispersion is presented and then the reported experimental studies on the determination of the effective thermal conductivity are summarized and compared. The reported experimental methods are classified into three groups: (1) heat addition/removal at the lateral boundaries, (2) heat addition at the inlet/outlet boundary, (3) heat addition inside the bed. For each performed study, the experimental details, methods, obtained results, and suggested correlations for the determination of the effective thermal conductivity are presented. The similarities and differences between experimental methods and reported studies are shown by tables. Comparison of the correlations for the effective thermal conductivity is made by using figures and the results of the studies are discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thermal dispersion is an important topic in the convective heat transfer in porous media. In order to determine the heat transfer in a packed bed, the effective thermal conductivity including both stagnant and dispersion thermal conductivities should be known. Several theoretical and experimental studies have been performed on the determination of the effective thermal conductivity. The aim of this study is to review the experimental studies done on the determination of the effective thermal conductivity of the packed beds. In this study, firstly brief information on the definition of the thermal dispersion is presented and then the reported experimental studies on the determination of the effective thermal conductivity are summarized and compared. The reported experimental methods are classified into three groups: (1) heat addition/removal at the lateral boundaries, (2) heat addition at the inlet/outlet boundary, (3) heat addition inside the bed. For each performed study, the experimental details, methods, obtained results, and suggested correlations for the determination of the effective thermal conductivity are presented. The similarities and differences between experimental methods and reported studies are shown by tables. Comparison of the correlations for the effective thermal conductivity is made by using figures and the results of the studies are discussed. |
Res. Assist. Dr. Hüseyin Sarıaltın
Internship Coordinator
Educational Background
B.Sc. Selcuk University, Mechanical Engineering, 2006
M.Sc. University of California – Riverside, Mechanical Engineering, 2010
Ph.D. Ege University, Solar Energy Institute, 2019
Research Interests
- Energy System Modelling
- Organic Photovoltaics Technologies
- +90 232 750 6788
- +90 232 750 6701
- Mechanical Engineering Building, Research Assistant Office-2 (Z46)
Publications
2025 |
Karagöz, Sadık Can; Gündoğdu, Tuğba Keskin; Sarıaltın, Hüseyin; Çeliktaş, Melih Soner A novel enzymatic delamination method for sustainable recycling of crystal silicon photovoltaic (c-Si PV) modules Journal Article 361 , 2025. @article{Karagöz2025, title = {A novel enzymatic delamination method for sustainable recycling of crystal silicon photovoltaic (c-Si PV) modules}, author = {Sadık Can Karagöz and Tuğba Keskin Gündoğdu and Hüseyin Sarıaltın and Melih Soner Çeliktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85213874973&doi=10.1016%2fj.seppur.2024.131373&partnerID=40&md5=d4d82dea8d5dd4941c227515919e2bfb}, doi = {10.1016/j.seppur.2024.131373}, year = {2025}, date = {2025-01-01}, volume = {361}, abstract = {Due to the growing effects of global warming, there has been a surge in the demand for renewable energy sources. In particular, the most important player in this increase is the installation of photovoltaic (PV) modules. At this critical stage, it has become a priority to identify strategic approaches for the recycling of end-of-life PV panels with a strong focus on environmental protection. This study examined the impact of enzymatic delamination on the separation of the EVA (Ethylne Viniyl Aceate Co polymer) layer, a crucial stage in the recycling process of PV panels. Notably, this investigation is the first of its kind in the existing literature. To investigate this, delamination effects of lipase, laccase, and lecitase enzymes were analyzed according to experimental design methods. Furthermore, sunflower oil was employed for the first time in the existing body of literature to facilitate delamination, resulting in a delamination rate of 100 %. The environmental impacts of these biotechnological techniques, which serve as alternatives to the commonly used toluene, were also comparatively assessed by life cycle assessment (LCA) method to analyze the environmental impact. LCA methodology was performed from gate to gate and the Recipe impact methodology was used. Oil assisted enzymatic delamination method was shown to be an alternative from environmental point of view to solvent based method such as toluene. © 2024 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Due to the growing effects of global warming, there has been a surge in the demand for renewable energy sources. In particular, the most important player in this increase is the installation of photovoltaic (PV) modules. At this critical stage, it has become a priority to identify strategic approaches for the recycling of end-of-life PV panels with a strong focus on environmental protection. This study examined the impact of enzymatic delamination on the separation of the EVA (Ethylne Viniyl Aceate Co polymer) layer, a crucial stage in the recycling process of PV panels. Notably, this investigation is the first of its kind in the existing literature. To investigate this, delamination effects of lipase, laccase, and lecitase enzymes were analyzed according to experimental design methods. Furthermore, sunflower oil was employed for the first time in the existing body of literature to facilitate delamination, resulting in a delamination rate of 100 %. The environmental impacts of these biotechnological techniques, which serve as alternatives to the commonly used toluene, were also comparatively assessed by life cycle assessment (LCA) method to analyze the environmental impact. LCA methodology was performed from gate to gate and the Recipe impact methodology was used. Oil assisted enzymatic delamination method was shown to be an alternative from environmental point of view to solvent based method such as toluene. © 2024 Elsevier B.V. |
Prof. Dr. Metin Tanoğlu
Educational Background
B.Sc. İstanbul Technical University, Turkey, Metallurgical and Materials Engineering, 1992
M.Sc. University of Delaware, USA, Materials Science & Engineering, 1996
Ph.D. University of Delaware, USA, Materials Science & Engineering, 2000
Research Interests
- Composite materials
- Mechanical, Physical, Thermal and Microstructural Characterization of Materials
- Impact/Ballistic Behavior of Materials
- Armor Materials
- Porous Materials
- Nanocomposites
- Layered Clays and Carbon Nanotubes (CNTs)
- +90 232 765 9091
- +90 232 750 6701
- Mechanical Engineering Building (106)
Publications
2024 |
Deveci, Hamza Arda; Artem, Hatice Seçil; Güneş, Mehmet Deniz; Tanoğlu, Metin 2024. @article{Deveci2024, title = {Fatigue-resistant design of carbon/epoxy composites based on a failure tensor polynomial model by particle swarm optimization-sequential quadratic programming algorithm}, author = {Hamza Arda Deveci and Hatice Seçil Artem and Mehmet Deniz Güneş and Metin Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85194821289&doi=10.1177%2f07316844241256815&partnerID=40&md5=1247ee8142b1887155d747393102dd2b}, doi = {10.1177/07316844241256815}, year = {2024}, date = {2024-01-01}, abstract = {This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024. |
Kiliçoğlu, Ahmet Süha; Tanoğlu, Metin; Bilmez, Sinan Ali; Güneş, Mehmet Deniz; Erdoğan, Hakan Salih Influence of intra-ply discontinuities on the mechanical behavior of continuous E-glass fiber reinforced composites Journal Article 58 (28), pp. 2955 – 2973, 2024. @article{Kiliçoğlu20242955, title = {Influence of intra-ply discontinuities on the mechanical behavior of continuous E-glass fiber reinforced composites}, author = {Ahmet Süha Kiliçoğlu and Metin Tanoğlu and Sinan Ali Bilmez and Mehmet Deniz Güneş and Hakan Salih Erdoğan}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85205575603&doi=10.1177%2f00219983241287754&partnerID=40&md5=b41c9b911772a90c5a63fe523d836e19}, doi = {10.1177/00219983241287754}, year = {2024}, date = {2024-01-01}, volume = {58}, number = {28}, pages = {2955 – 2973}, abstract = {This study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure’s discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities’ impact on the composite laminate’s mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts’ structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component’s zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability. © The Author(s) 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure’s discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities’ impact on the composite laminate’s mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts’ structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component’s zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability. © The Author(s) 2024. |
Taşkıran, Senagül Tunca; Tanoğlu, Metin; Çerci, Nazife; Cevahir, Aref; Damar, Ceren Türkdoğan; Ünver, Elçin; Aktaş, Mustafa İlker Development of resin-based dental composites containing hydroxyapatite and zirconia nanoparticles Journal Article 45 (11), pp. 10470 – 10485, 2024. @article{TuncaTaşkıran202410470, title = {Development of resin-based dental composites containing hydroxyapatite and zirconia nanoparticles}, author = {Senagül Tunca Taşkıran and Metin Tanoğlu and Nazife Çerci and Aref Cevahir and Ceren Türkdoğan Damar and Elçin Ünver and Mustafa İlker Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85192195777&doi=10.1002%2fpc.28488&partnerID=40&md5=e1bddd711ce08dadf4e46669d071d6ae}, doi = {10.1002/pc.28488}, year = {2024}, date = {2024-01-01}, volume = {45}, number = {11}, pages = {10470 – 10485}, abstract = {In clinical applications, resin-based dental composites primarily face challenges with fractures and secondary caries. To overcome these issues, the physical characteristics of dental composites, especially mechanical properties, need to be improved. Hydroxyapatite (HA), present in the structure of the teeth, is preferred due to its biological properties, and zirconia (ZrO2) nanoparticles are known to enhance the mechanical properties of this type of composites. The aim of this study is to develop resin-based dental composites containing HA and ZrO2 nanoparticles. The study also aims to explore the synergistic effect of these two nanoparticles on the physical properties of the developed composites. Composites with nine different compositions were prepared by mixing the components with the help of a mortar mill. The flexural and compressive strength, polymerization shrinkage, depth of cure and water sorption, and solubility properties of the prepared composites have been investigated. All composites have been found to meet the requirements of ISO 4049 standard. Among them, composite containing 5 wt. % HA and 1 wt. % ZrO2 (H5Z1) has exhibited the highest flexural strength with an increase of 58% compared to the control sample, and composite containing 3 wt. % HA and 2 wt. % ZrO2 (H3Z2) has exhibited the highest compressive strength with an increase of 22% compared to the control sample. Other physical properties of the composites have been found to be in an acceptable level. Highlights: Dental composites with HA and ZrO2 fillers were developed by a mortar mill. Synergistic effect of HA and ZrO2 nanoparticles was investigated. Mechanical properties of dental composites were significantly improved. Physical properties of dental composites were found to be at acceptable levels. Depth of cure decreases with increasing HA and ZrO2 loading. © 2024 The Authors. Polymer Composites published by Wiley Periodicals LLC on behalf of Society of Plastics Engineers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In clinical applications, resin-based dental composites primarily face challenges with fractures and secondary caries. To overcome these issues, the physical characteristics of dental composites, especially mechanical properties, need to be improved. Hydroxyapatite (HA), present in the structure of the teeth, is preferred due to its biological properties, and zirconia (ZrO2) nanoparticles are known to enhance the mechanical properties of this type of composites. The aim of this study is to develop resin-based dental composites containing HA and ZrO2 nanoparticles. The study also aims to explore the synergistic effect of these two nanoparticles on the physical properties of the developed composites. Composites with nine different compositions were prepared by mixing the components with the help of a mortar mill. The flexural and compressive strength, polymerization shrinkage, depth of cure and water sorption, and solubility properties of the prepared composites have been investigated. All composites have been found to meet the requirements of ISO 4049 standard. Among them, composite containing 5 wt. % HA and 1 wt. % ZrO2 (H5Z1) has exhibited the highest flexural strength with an increase of 58% compared to the control sample, and composite containing 3 wt. % HA and 2 wt. % ZrO2 (H3Z2) has exhibited the highest compressive strength with an increase of 22% compared to the control sample. Other physical properties of the composites have been found to be in an acceptable level. Highlights: Dental composites with HA and ZrO2 fillers were developed by a mortar mill. Synergistic effect of HA and ZrO2 nanoparticles was investigated. Mechanical properties of dental composites were significantly improved. Physical properties of dental composites were found to be at acceptable levels. Depth of cure decreases with increasing HA and ZrO2 loading. © 2024 The Authors. Polymer Composites published by Wiley Periodicals LLC on behalf of Society of Plastics Engineers. |
Yeke, Melisa; Barisik, Murat; Tanoğlu, Metin; Ulaşlı, Erdal M; Nuhoğlu, Kaan; Esenoğlu, Gözde; Martin, Seçkin; Türkdoğan, Ceren; İplikçi, Hande; Aktaş, Engin; Dehneliler, Serkan; İriş, Erdem M 337 , 2024. @article{Yeke2024, title = {Improving mechanical behavior of adhesively bonded composite joints by incorporating reduced graphene oxide added polyamide 6,6 electrospun nanofibers}, author = {Melisa Yeke and Murat Barisik and Metin Tanoğlu and M Erdal Ulaşlı and Kaan Nuhoğlu and Gözde Esenoğlu and Seçkin Martin and Ceren Türkdoğan and Hande İplikçi and Engin Aktaş and Serkan Dehneliler and M Erdem İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85188729566&doi=10.1016%2fj.compstruct.2024.118026&partnerID=40&md5=b6e635bcb6124a266395341064377db8}, doi = {10.1016/j.compstruct.2024.118026}, year = {2024}, date = {2024-01-01}, volume = {337}, abstract = {Adhesive joining of fiber-reinforced polymer (FRP) composites requires adequate interface tailoring and careful surface preparation to obtain a strong bond between components. This study aimed to improve the mechanical performance of adhesively bonded unidirectional carbon fiber-based (CFRP) composite parts by modifying joint surfaces with graphene-added electrospun Polyamide 6,6 (PA66) nanofibers. Reduced graphene oxide (rGO) was dispersed at 10 % wt/v PA66 solution at three different concentrations below rGO saturation limits. Bead-free nanofibers with homogenous graphene distribution were obtained on a prepreg by electrospinning. Addition of up to 2 % rGO yielded complete dispersion through the nanofiber network while the higher values created local agglomerations. Surface wetting experiments showed conversion of slightly hydrophobic surfaces to complete hydrophilic with electrospun nanofiber coating and the lowest contact angle was obtained at 2 % wt/v rGO addition (26.18°±2.03°). Composite plates were produced in a hot press keeping the modified prepregs on top. Plates with different surface treatments joined by secondary bonding using 3 plies of FM 300 K film adhesive. Mechanical properties of adhesively bonded composites were tested by Single lap joint and Charpy impact tests. We achieved an 18 % increase in shear strength and 31 % increase in impact strength by adding 2 % wt/v ratio rGO into PA66 electrospun nanofiber. © 2024 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Adhesive joining of fiber-reinforced polymer (FRP) composites requires adequate interface tailoring and careful surface preparation to obtain a strong bond between components. This study aimed to improve the mechanical performance of adhesively bonded unidirectional carbon fiber-based (CFRP) composite parts by modifying joint surfaces with graphene-added electrospun Polyamide 6,6 (PA66) nanofibers. Reduced graphene oxide (rGO) was dispersed at 10 % wt/v PA66 solution at three different concentrations below rGO saturation limits. Bead-free nanofibers with homogenous graphene distribution were obtained on a prepreg by electrospinning. Addition of up to 2 % rGO yielded complete dispersion through the nanofiber network while the higher values created local agglomerations. Surface wetting experiments showed conversion of slightly hydrophobic surfaces to complete hydrophilic with electrospun nanofiber coating and the lowest contact angle was obtained at 2 % wt/v rGO addition (26.18°±2.03°). Composite plates were produced in a hot press keeping the modified prepregs on top. Plates with different surface treatments joined by secondary bonding using 3 plies of FM 300 K film adhesive. Mechanical properties of adhesively bonded composites were tested by Single lap joint and Charpy impact tests. We achieved an 18 % increase in shear strength and 31 % increase in impact strength by adding 2 % wt/v ratio rGO into PA66 electrospun nanofiber. © 2024 Elsevier Ltd |
Nuhoglu, Kaan; Aktas, Engin; Tanoglu, Metin; Barisik, Murat; Esenoglu, Gözde; Martin, Seckin; Iplikci, Hande; Yeke, Melisa; Türkdoğan, Ceren; Dehneliler, Serkan; Iris, Mehmet Erdem Multi-scale analysis of the adhesive bonding behavior of laser surface-treated carbon fiber reinforced polymer composite structures Journal Article 130 , 2024. @article{Nuhoglu2024, title = {Multi-scale analysis of the adhesive bonding behavior of laser surface-treated carbon fiber reinforced polymer composite structures}, author = {Kaan Nuhoglu and Engin Aktas and Metin Tanoglu and Murat Barisik and Gözde Esenoglu and Seckin Martin and Hande Iplikci and Melisa Yeke and Ceren Türkdoğan and Serkan Dehneliler and Mehmet Erdem Iris}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85185478746&doi=10.1016%2fj.ijadhadh.2024.103643&partnerID=40&md5=843a16689f4b7773484a58c349bf1d9d}, doi = {10.1016/j.ijadhadh.2024.103643}, year = {2024}, date = {2024-01-01}, volume = {130}, abstract = {Laser surface treatment has considerable potential to provide high-quality adhesive-joining of carbon-fiber-reinforced polymer (CFRP) composites by removing contaminants and the top polymer layer and increasing the surface roughness without damaging the fibers. Yet, predicting the failure strength and mechanism of the laser surface-treated adhesively bonded joints under static and cyclic loads is important to designing reliable structures. In this study, a multi-scale Finite Element Analysis (FEA) of the adhesively bonded CFRP composite structures was developed to accurately predict the failure load and damage growth. Numerical simulations of the single lap joint (SLJ) specimen was executed, employing the cohesive zone modeling (CZM) technique between adjacent surfaces to simulate the bonding behavior of the secondary bonded CFRP parts. Using the homogenization procedure, the micro-scale simulation of the contact region of the laser-treated adherent surface and adhesive was performed to extract traction separation law (TSL) parameters. The mechanical interlocking contribution of the laser surface treatment was imported to the macro-scale FEA, analyzing the representative volume element (RVE) of the bonding interface region. We presented that the multi-scale analysis estimated the experimentally measured mechanical behaviour, strength values, and failure modes successfully with a negligible error (7 %). © 2024 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Laser surface treatment has considerable potential to provide high-quality adhesive-joining of carbon-fiber-reinforced polymer (CFRP) composites by removing contaminants and the top polymer layer and increasing the surface roughness without damaging the fibers. Yet, predicting the failure strength and mechanism of the laser surface-treated adhesively bonded joints under static and cyclic loads is important to designing reliable structures. In this study, a multi-scale Finite Element Analysis (FEA) of the adhesively bonded CFRP composite structures was developed to accurately predict the failure load and damage growth. Numerical simulations of the single lap joint (SLJ) specimen was executed, employing the cohesive zone modeling (CZM) technique between adjacent surfaces to simulate the bonding behavior of the secondary bonded CFRP parts. Using the homogenization procedure, the micro-scale simulation of the contact region of the laser-treated adherent surface and adhesive was performed to extract traction separation law (TSL) parameters. The mechanical interlocking contribution of the laser surface treatment was imported to the macro-scale FEA, analyzing the representative volume element (RVE) of the bonding interface region. We presented that the multi-scale analysis estimated the experimentally measured mechanical behaviour, strength values, and failure modes successfully with a negligible error (7 %). © 2024 Elsevier Ltd |
Deveci, Hamza Arda; Artem, Hatice Seçil; Güneş, Mehmet Deniz; Tanoğlu, Metin 2024. @article{Deveci2024b, title = {Fatigue-resistant design of carbon/epoxy composites based on a failure tensor polynomial model by particle swarm optimization-sequential quadratic programming algorithm}, author = {Hamza Arda Deveci and Hatice Seçil Artem and Mehmet Deniz Güneş and Metin Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85194821289&doi=10.1177%2f07316844241256815&partnerID=40&md5=1247ee8142b1887155d747393102dd2b}, doi = {10.1177/07316844241256815}, year = {2024}, date = {2024-01-01}, abstract = {This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm’s performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications. © The Author(s) 2024. |
2023 |
İplikçi, Hande; Barisik, Murat; Türkdoğan, Ceren; Martin, Seçkin; Yeke, Melisa; Nuhoğlu, Kaan; Esenoğlu, Gözde; Tanoğlu, Metin; Aktaş, Engin; Dehneliler, Serkan; İriş, Mehmet Erdem Effects of nanosecond laser ablation parameters on surface modification of carbon fiber reinforced polymer composites Journal Article Journal of Composite Materials, 57 (18), pp. 2843 – 2855, 2023. @article{İplikçi20232843, title = {Effects of nanosecond laser ablation parameters on surface modification of carbon fiber reinforced polymer composites}, author = {Hande İplikçi and Murat Barisik and Ceren Türkdoğan and Seçkin Martin and Melisa Yeke and Kaan Nuhoğlu and Gözde Esenoğlu and Metin Tanoğlu and Engin Aktaş and Serkan Dehneliler and Mehmet Erdem İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162945413&doi=10.1177%2f00219983231178892&partnerID=40&md5=1e698a002a7d62e7f42a2444aafff1d5}, doi = {10.1177/00219983231178892}, year = {2023}, date = {2023-01-01}, journal = {Journal of Composite Materials}, volume = {57}, number = {18}, pages = {2843 – 2855}, abstract = {Removal of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/−45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Removal of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/−45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023. |
Nuhoğlu, Kaan; Aktaş, Engin; Tanoğlu, Metin; Martin, Seçkin; İplikçi, Hande; Barışık, Murat; Yeke, Melisa; Türkdoğan, Ceren; Esenoğlu, Gözde; Dehneliler, Serkan; İriş, Mehmet Erdem Analysis of adhesively bonded joints of laser surface treated composite primary components of aircraft structures Journal Article International Journal of Adhesion and Adhesives, 126 , 2023. @article{Nuhoğlu2023, title = {Analysis of adhesively bonded joints of laser surface treated composite primary components of aircraft structures}, author = {Kaan Nuhoğlu and Engin Aktaş and Metin Tanoğlu and Seçkin Martin and Hande İplikçi and Murat Barışık and Melisa Yeke and Ceren Türkdoğan and Gözde Esenoğlu and Serkan Dehneliler and Mehmet Erdem İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85166291425&doi=10.1016%2fj.ijadhadh.2023.103456&partnerID=40&md5=aa5024e2ac1955cb1a3ff85d46fc3589}, doi = {10.1016/j.ijadhadh.2023.103456}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Adhesion and Adhesives}, volume = {126}, abstract = {The performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box. © 2023 Elsevier Ltd |
Esenoğlu, Gözde; Tanoğlu, Metin; Barisik, Murat; İplikçi, Hande; Yeke, Melisa; Nuhoğlu, Kaan; Türkdoğan, Ceren; Martin, Seçkin; Aktaş, Engin; Dehneliler, Serkan; Gürbüz, Ahmet Ayberk; İriş, Mehmet Erdem Investigating the Effects of PA66 Electrospun Nanofibers Layered within an Adhesive Composite Joint Fabricated under Autoclave Curing Journal Article ACS Omega, 8 (36), pp. 32656 – 32666, 2023, (All Open Access, Gold Open Access, Green Open Access). @article{Esenoğlu202332656, title = {Investigating the Effects of PA66 Electrospun Nanofibers Layered within an Adhesive Composite Joint Fabricated under Autoclave Curing}, author = {Gözde Esenoğlu and Metin Tanoğlu and Murat Barisik and Hande İplikçi and Melisa Yeke and Kaan Nuhoğlu and Ceren Türkdoğan and Seçkin Martin and Engin Aktaş and Serkan Dehneliler and Ahmet Ayberk Gürbüz and Mehmet Erdem İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85172448706&doi=10.1021%2facsomega.3c03419&partnerID=40&md5=7f3ddea2390eb013c802b710a5aaf695}, doi = {10.1021/acsomega.3c03419}, year = {2023}, date = {2023-01-01}, journal = {ACS Omega}, volume = {8}, number = {36}, pages = {32656 – 32666}, abstract = {Enhancing the performance of adhesively joined composite components is crucial for various industrial applications. In this study, polyamide 66 (PA66) nanofibers produced by electrospinning were coated on unidirectional carbon/epoxy prepregs to increase the bond strength of the composites. Carbon/epoxy prepregs with/without PA66 nanofiber coating on the bonding region were fabricated using the autoclave, which is often used in the aerospace industry. The single lap shear Charpy impact energy and Mode-I fracture toughness tests were employed to examine the effects of PA66 nanofibers on the mechanical properties of the joint region. Scanning electron microscopy (SEM) was used to investigate the nanofiber morphology and fracture modes. The thermal characteristics of Polyamide 66 nanofibers were explored by using differential scanning calorimetry (DSC). We observed that the electrospun PA66 nanofiber coating on the prepreg surfaces substantially improves the joint strength. Results revealed that the single lap shear and Charpy impact strength values of the composite joint are increased by about 79 and 24%, respectively, by coating PA66 nanofibers onto the joining region. The results also showed that by coating PA66 nanofibers, the Mode-I fracture toughness value was improved by about 107% while the glass transition temperature remained constant. © 2023 The Authors. Published by American Chemical Society.}, note = {All Open Access, Gold Open Access, Green Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Enhancing the performance of adhesively joined composite components is crucial for various industrial applications. In this study, polyamide 66 (PA66) nanofibers produced by electrospinning were coated on unidirectional carbon/epoxy prepregs to increase the bond strength of the composites. Carbon/epoxy prepregs with/without PA66 nanofiber coating on the bonding region were fabricated using the autoclave, which is often used in the aerospace industry. The single lap shear Charpy impact energy and Mode-I fracture toughness tests were employed to examine the effects of PA66 nanofibers on the mechanical properties of the joint region. Scanning electron microscopy (SEM) was used to investigate the nanofiber morphology and fracture modes. The thermal characteristics of Polyamide 66 nanofibers were explored by using differential scanning calorimetry (DSC). We observed that the electrospun PA66 nanofiber coating on the prepreg surfaces substantially improves the joint strength. Results revealed that the single lap shear and Charpy impact strength values of the composite joint are increased by about 79 and 24%, respectively, by coating PA66 nanofibers onto the joining region. The results also showed that by coating PA66 nanofibers, the Mode-I fracture toughness value was improved by about 107% while the glass transition temperature remained constant. © 2023 The Authors. Published by American Chemical Society. |
Uz, Yusuf Can; Tanoğlu, Metin Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry Journal Article High Performance Polymers, 35 (2), pp. 166 – 180, 2023. @article{Uz2023166, title = {Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry}, author = {Yusuf Can Uz and Metin Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85135891731&doi=10.1177%2f09540083221115987&partnerID=40&md5=4b3d7c567d57a6b645d854737e03917d}, doi = {10.1177/09540083221115987}, year = {2023}, date = {2023-01-01}, journal = {High Performance Polymers}, volume = {35}, number = {2}, pages = {166 – 180}, abstract = {The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods. © The Author(s) 2022. |
2021 |
Kangal, Serkan; Say, Harun A; Ayakda, Ozan; Kartav, Osman; Aydin, Levent; Artem, Secil H; Aktas, Engin; Yuceturk, Kutay; Tanoglu, Metin; Kandemir, Sinan; Beylergil, Bertan A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels Journal Article JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, 143 (4), 2021. @article{WOS:000669955100012, title = {A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels}, author = {Serkan Kangal and Harun A Say and Ozan Ayakda and Osman Kartav and Levent Aydin and Secil H Artem and Engin Aktas and Kutay Yuceturk and Metin Tanoglu and Sinan Kandemir and Bertan Beylergil}, doi = {10.1115/1.4049644}, year = {2021}, date = {2021-08-01}, journal = {JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, volume = {143}, number = {4}, abstract = {This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis. |
2020 |
Beylergil, Bertan; Tanoglu, Metin; Aktas, Engin Experimental and statistical analysis of carbon fiber/epoxy composites interleaved with nylon 6,6 nonwoven fabric interlayers Journal Article JOURNAL OF COMPOSITE MATERIALS, 54 (27), pp. 4173-4184, 2020, ISSN: 0021-9983. @article{ISI:000535519800001, title = {Experimental and statistical analysis of carbon fiber/epoxy composites interleaved with nylon 6,6 nonwoven fabric interlayers}, author = {Bertan Beylergil and Metin Tanoglu and Engin Aktas}, doi = {10.1177/0021998320927740, Early Access Date = MAY 2020}, issn = {0021-9983}, year = {2020}, date = {2020-11-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {54}, number = {27}, pages = {4173-4184}, abstract = {Thermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively. |
Yardimci, Atike Ince; Tanoglu, Metin; Yilmaz, Selahattin; Selamet, Yusuf Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method Journal Article TURKISH JOURNAL OF CHEMISTRY, 44 (4), pp. 1002-1015, 2020, ISSN: 1300-0527. @article{ISI:000560919000010, title = {Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method}, author = {Atike Ince Yardimci and Metin Tanoglu and Selahattin Yilmaz and Yusuf Selamet}, doi = {10.3906/kim-1911-49}, issn = {1300-0527}, year = {2020}, date = {2020-01-01}, journal = {TURKISH JOURNAL OF CHEMISTRY}, volume = {44}, number = {4}, pages = {1002-1015}, abstract = {In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold. |
2017 |
Beylergil, Bertan; Tanoglu, Metin; Aktas, Engin Enhancement of interlaminar fracture toughness of carbon fiber-epoxy composites using polyamide-6,6 electrospun nanofibers Journal Article JOURNAL OF APPLIED POLYMER SCIENCE, 134 (35), 2017, ISSN: 0021-8995. @article{ISI:000403346000012, title = {Enhancement of interlaminar fracture toughness of carbon fiber-epoxy composites using polyamide-6,6 electrospun nanofibers}, author = {Bertan Beylergil and Metin Tanoglu and Engin Aktas}, doi = {10.1002/app.45244}, issn = {0021-8995}, year = {2017}, date = {2017-09-01}, journal = {JOURNAL OF APPLIED POLYMER SCIENCE}, volume = {134}, number = {35}, abstract = {In this study, carbon fiber-epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber-epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. |
2016 |
Merter, Emrah N; Baser, Gulnur; Tanoglu, Metin JOURNAL OF COMPOSITE MATERIALS, 50 (12, SI), pp. 1697-1706, 2016, ISSN: 0021-9983. @article{ISI:000374328300014, title = {Effects of hybrid yarn preparation technique and fiber sizing on the mechanical properties of continuous glass fiber-reinforced polypropylene composites}, author = {Emrah N Merter and Gulnur Baser and Metin Tanoglu}, doi = {10.1177/0021998315595710}, issn = {0021-9983}, year = {2016}, date = {2016-05-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {50}, number = {12, SI}, pages = {1697-1706}, abstract = {In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with +/- 45 degrees fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with +/- 45 degrees fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites. |
Merter, Emrah N; Başer, Gülnur; Tanoğlu, Metin Journal of Composite Materials, 50 (12), pp. 1697-1706, 2016. @article{doi:10.1177/0021998315595710, title = {Effects of hybrid yarn preparation technique and fiber sizing on the mechanical properties of continuous glass fiber-reinforced polypropylene composites}, author = {Emrah N Merter and Gülnur Başer and Metin Tanoğlu}, url = {https://doi.org/10.1177/0021998315595710}, doi = {10.1177/0021998315595710}, year = {2016}, date = {2016-01-01}, journal = {Journal of Composite Materials}, volume = {50}, number = {12}, pages = {1697-1706}, abstract = {In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with ± 45 ° fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1 MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87 N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with ± 45 ° fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1 MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87 N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites. |
2011 |
Basturk, Bahar S; Tanoglu, Metin Mechanical and energy absorption behaviors of metal/polymer layered sandwich structures Journal Article JOURNAL OF REINFORCED PLASTICS AND COMPOSITES, 30 (18), pp. 1539-1547, 2011, ISSN: 0731-6844. @article{ISI:000297764900003, title = {Mechanical and energy absorption behaviors of metal/polymer layered sandwich structures}, author = {Bahar S Basturk and Metin Tanoglu}, doi = {10.1177/0731684411421844}, issn = {0731-6844}, year = {2011}, date = {2011-09-01}, journal = {JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, volume = {30}, number = {18}, pages = {1539-1547}, abstract = {This article considers the sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of fibre-metal laminates (FML). The FMLs with Al sheet and glass fiber reinforced polypropylene (GFPP) composites were integrated with Al foam for composing the sandwich panels. The FML-foam sandwich systems were manufactured by hot pressing in a mold at 200 degrees C under 1.5 MPa pressure. The bonding between the components of the sandwich was achieved by various surface modification techniques, i.e., silane surface treatment, PP adhesive film additition, and their combination. The Al sheet/Al foam sandwiches were also prepared by bonding the components with an epoxy adhesive for comparing the effect of GFPP on the mechanical performance of the sandwich structures. The energy absorption capacities together with compressive mechanical behavior of both Al foams and FML-foam sandwich systems were evaluated by flatwise compression tests. Experiments were performed on samples of varying foam thicknesses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article considers the sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of fibre-metal laminates (FML). The FMLs with Al sheet and glass fiber reinforced polypropylene (GFPP) composites were integrated with Al foam for composing the sandwich panels. The FML-foam sandwich systems were manufactured by hot pressing in a mold at 200 degrees C under 1.5 MPa pressure. The bonding between the components of the sandwich was achieved by various surface modification techniques, i.e., silane surface treatment, PP adhesive film additition, and their combination. The Al sheet/Al foam sandwiches were also prepared by bonding the components with an epoxy adhesive for comparing the effect of GFPP on the mechanical performance of the sandwich structures. The energy absorption capacities together with compressive mechanical behavior of both Al foams and FML-foam sandwich systems were evaluated by flatwise compression tests. Experiments were performed on samples of varying foam thicknesses. |
2010 |
Yurdakul, Hilmi; Seyhan, Tugrul A; Turan, Servet; Tanoglu, Metin; Bauhofer, Wolfgang; Schulte, Karl Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties Journal Article COMPOSITES SCIENCE AND TECHNOLOGY, 70 (14), pp. 2102-2110, 2010, ISSN: 0266-3538. @article{ISI:000283759400010, title = {Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties}, author = {Hilmi Yurdakul and Tugrul A Seyhan and Servet Turan and Metin Tanoglu and Wolfgang Bauhofer and Karl Schulte}, doi = {10.1016/j.compscitech.2010.08.007}, issn = {0266-3538}, year = {2010}, date = {2010-11-01}, journal = {COMPOSITES SCIENCE AND TECHNOLOGY}, volume = {70}, number = {14}, pages = {2102-2110}, abstract = {In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T-g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T-g than the composites cured without application of the AC electric field. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T-g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T-g than the composites cured without application of the AC electric field. (C) 2010 Elsevier Ltd. All rights reserved. |
Coskun, Selim; Ovecoglu, Lutfi M; Ozkal, Burak; Tanoglu, Metin Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites Journal Article JOURNAL OF ALLOYS AND COMPOUNDS, 492 (1-2), pp. 576-584, 2010, ISSN: 0925-8388. @article{ISI:000276018900125, title = {Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites}, author = {Selim Coskun and Lutfi M Ovecoglu and Burak Ozkal and Metin Tanoglu}, doi = {10.1016/j.jallcom.2009.11.185}, issn = {0925-8388}, year = {2010}, date = {2010-03-01}, journal = {JOURNAL OF ALLOYS AND COMPOUNDS}, volume = {492}, number = {1-2}, pages = {576-584}, abstract = {The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H(2) gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H(2) gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved. |
2009 |
Seyhan, Tugrul A; Tanoglu, Metin; Schulte, Karl MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 523 (1-2), pp. 85-92, 2009, ISSN: 0921-5093. @article{ISI:000270632900014, title = {Tensile mechanical behavior and fracture toughness of MWCNT and DWCNT modified vinyl-ester/polyester hybrid nanocomposites produced by 3-roll milling}, author = {Tugrul A Seyhan and Metin Tanoglu and Karl Schulte}, doi = {10.1016/j.msea.2009.05.035}, issn = {0921-5093}, year = {2009}, date = {2009-10-01}, journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, volume = {523}, number = {1-2}, pages = {85-92}, abstract = {This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH2 and DWCNT-NH2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH2, MWCNTs and MWCNT-NH2 were fitted to Halphin-Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites. (C) 2009 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH2 and DWCNT-NH2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH2, MWCNTs and MWCNT-NH2 were fitted to Halphin-Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites. (C) 2009 Elsevier B.V. All rights reserved. |
2008 |
Seyhan, Tugrul A; Tanoglu, Metin; Schulte, Karl Mode I and mode II fracture toughness of E-glass non-crimp fabric/carbon nanotube (CNT) modified polymer based composites Journal Article ENGINEERING FRACTURE MECHANICS, 75 (18), pp. 5151-5162, 2008, ISSN: 0013-7944. @article{ISI:000261562000013, title = {Mode I and mode II fracture toughness of E-glass non-crimp fabric/carbon nanotube (CNT) modified polymer based composites}, author = {Tugrul A Seyhan and Metin Tanoglu and Karl Schulte}, doi = {10.1016/j.engfracmech.2008.08.003}, issn = {0013-7944}, year = {2008}, date = {2008-12-01}, journal = {ENGINEERING FRACTURE MECHANICS}, volume = {75}, number = {18}, pages = {5151-5162}, abstract = {In this study, mode I and mode II interlaminar fracture toughness, and interlaminar shear strength of E-glass non-crimp fabric/carbon nanotube modified polymer matrix composites were investigated. The matrix resin containing 0.1 wt.% of amino functionalized multi walled carbon nanotubes were prepared, utilizing the 3-roll milling technique. Composite laminates were manufactured via vacuum assisted resin transfer molding process. Carbon nanotube modified laminates were found to exhibit 8% and 11% higher mode 11 interlaminar fracture toughness and interlaminar shear strength values, respectively, as compared to the base laminates. However, no significant improvement was observed for mode I interlaminar fracture toughness values. Furthermore, Optical microscopy and scanning electron microscopy were utilized to monitor the distribution of carbon nanotubes within the composite microstructure and to examine the fracture surfaces of the failed specimens, respectively. (c) 2008 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, mode I and mode II interlaminar fracture toughness, and interlaminar shear strength of E-glass non-crimp fabric/carbon nanotube modified polymer matrix composites were investigated. The matrix resin containing 0.1 wt.% of amino functionalized multi walled carbon nanotubes were prepared, utilizing the 3-roll milling technique. Composite laminates were manufactured via vacuum assisted resin transfer molding process. Carbon nanotube modified laminates were found to exhibit 8% and 11% higher mode 11 interlaminar fracture toughness and interlaminar shear strength values, respectively, as compared to the base laminates. However, no significant improvement was observed for mode I interlaminar fracture toughness values. Furthermore, Optical microscopy and scanning electron microscopy were utilized to monitor the distribution of carbon nanotubes within the composite microstructure and to examine the fracture surfaces of the failed specimens, respectively. (c) 2008 Elsevier Ltd. All rights reserved. |
Kaya, Elcin; Tanoglu, Metin; Okur, Salih Layered clay/epoxy nanocomposites: Thermomechanical, flame retardancy, and optical properties Journal Article JOURNAL OF APPLIED POLYMER SCIENCE, 109 (2), pp. 834-840, 2008, ISSN: 0021-8995. @article{ISI:000256267200020, title = {Layered clay/epoxy nanocomposites: Thermomechanical, flame retardancy, and optical properties}, author = {Elcin Kaya and Metin Tanoglu and Salih Okur}, doi = {10.1002/app.28168}, issn = {0021-8995}, year = {2008}, date = {2008-07-01}, journal = {JOURNAL OF APPLIED POLYMER SCIENCE}, volume = {109}, number = {2}, pages = {834-840}, abstract = {In this study, layered clay/polymer nanocomposites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ion exchange reaction. In this way, Na+ interlayer cations of the clay is exchanged with onium cation of the surfactant that turns the hydrophilic clays (MMT) to organophilic (OMMT) characteristics. Thermal analysis results revealed that the glass transition temperature (T-g) and the dynamic mechanical properties including the storage and loss modulus of the neat epoxy resin increases by the incorporation of clay particles. It was also found that flame resistance of the polymer is improved by the addition of the clay particles. (C) 2008 Wiley Periodicals, Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, layered clay/polymer nanocomposites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ion exchange reaction. In this way, Na+ interlayer cations of the clay is exchanged with onium cation of the surfactant that turns the hydrophilic clays (MMT) to organophilic (OMMT) characteristics. Thermal analysis results revealed that the glass transition temperature (T-g) and the dynamic mechanical properties including the storage and loss modulus of the neat epoxy resin increases by the incorporation of clay particles. It was also found that flame resistance of the polymer is improved by the addition of the clay particles. (C) 2008 Wiley Periodicals, Inc. |
Alpöz, Riza A; Ertuḡrul, Fahinur; Cogulu, Dilsah; Ak, Asli Topaloḡlu; Tanoḡlu, Metin; ç, El Effects of light curing method and exposure time on mechanical properties of resin based dental materials Journal Article European journal of dentistry, 2 , pp. 37, 2008. @article{alpoz2008effects, title = {Effects of light curing method and exposure time on mechanical properties of resin based dental materials}, author = {Riza A Alpöz and Fahinur Ertuḡrul and Dilsah Cogulu and Asli Topaloḡlu Ak and Metin Tanoḡlu and El{ç}in Kaya}, year = {2008}, date = {2008-01-01}, journal = {European journal of dentistry}, volume = {2}, pages = {37}, publisher = {Dental Investigations Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2007 |
Bozkurt, Emrah; Kaya, Elcin; Tanoglu, Metin Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites Journal Article COMPOSITES SCIENCE AND TECHNOLOGY, 67 (15-16), pp. 3394-3403, 2007, ISSN: 0266-3538. @article{ISI:000250910600040, title = {Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites}, author = {Emrah Bozkurt and Elcin Kaya and Metin Tanoglu}, doi = {10.1016/j.compscitech.2007.03.021}, issn = {0266-3538}, year = {2007}, date = {2007-12-01}, journal = {COMPOSITES SCIENCE AND TECHNOLOGY}, volume = {67}, number = {15-16}, pages = {3394-3403}, abstract = {Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy natiocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T-g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix. (C) 2007 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy natiocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T-g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix. (C) 2007 Elsevier Ltd. All rights reserved. |
Simsek, Yilmaz; Ozyuzer, Lutfi; Seyhan, Tugrul A; Tanoglu, Metin; Schulte, Karl Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites Journal Article JOURNAL OF MATERIALS SCIENCE, 42 (23), pp. 9689-9695, 2007, ISSN: 0022-2461. @article{ISI:000249657500026, title = {Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites}, author = {Yilmaz Simsek and Lutfi Ozyuzer and Tugrul A Seyhan and Metin Tanoglu and Karl Schulte}, doi = {10.1007/s10853-007-1943-9}, issn = {0022-2461}, year = {2007}, date = {2007-12-01}, journal = {JOURNAL OF MATERIALS SCIENCE}, volume = {42}, number = {23}, pages = {9689-9695}, abstract = {The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (-NH2). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (-NH2). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model. |
Seyhan, Tugrul A; Gojny, Florian H; Tanoglu, Metin; Schulte, Karl Critical aspects related to processing of carbon nano tube/unsaturated thermoset polyester nanocomposites Journal Article EUROPEAN POLYMER JOURNAL, 43 (2), pp. 374-379, 2007, ISSN: 0014-3057. @article{ISI:000244379900010, title = {Critical aspects related to processing of carbon nano tube/unsaturated thermoset polyester nanocomposites}, author = {Tugrul A Seyhan and Florian H Gojny and Metin Tanoglu and Karl Schulte}, doi = {10.1016/j.eurpolymj.2006.11.018}, issn = {0014-3057}, year = {2007}, date = {2007-02-01}, journal = {EUROPEAN POLYMER JOURNAL}, volume = {43}, number = {2}, pages = {374-379}, abstract = {Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix. (c) 2006 Elsevier Ltd. All rights reserved. |
Tanoglu, Metin; Ergun, Yelda Porous nanocomposites prepared from layered clay and PMMA [poly(methyl methacrylate)] Journal Article COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, 38 (2), pp. 318-322, 2007, ISSN: 1359-835X. @article{ISI:000244008900011, title = {Porous nanocomposites prepared from layered clay and PMMA [poly(methyl methacrylate)]}, author = {Metin Tanoglu and Yelda Ergun}, doi = {10.1016/j.compositesa.2006.04.002}, issn = {1359-835X}, year = {2007}, date = {2007-01-01}, journal = {COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, volume = {38}, number = {2}, pages = {318-322}, abstract = {The aim of the present work is the preparation of PMMA based porous nanocomposites that contain clay (montmorillonite, MMT) platelets as reinforcements within the cell walls of the porous structure. To render the clay layers organophilic, MMT was surface treated by an ion exchange reaction between interlayer cations of the clay and ammonium ions of a surfactant. Clay/PMMA based porous nanocomposites were prepared by polymerization of water-in-oil emulsions with and without clay addition. The microstructure and compressive mechanical behavior of the nanocomposites were investigated. The results of mechanical tests showed that the porous systems with the addition of 1 wt.% of organoclay (OMNIT) exhibited a 90% and 50% increase of collapse stress and elastic modulus values, respectively, as compared to neat porous PMMA. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of the present work is the preparation of PMMA based porous nanocomposites that contain clay (montmorillonite, MMT) platelets as reinforcements within the cell walls of the porous structure. To render the clay layers organophilic, MMT was surface treated by an ion exchange reaction between interlayer cations of the clay and ammonium ions of a surfactant. Clay/PMMA based porous nanocomposites were prepared by polymerization of water-in-oil emulsions with and without clay addition. The microstructure and compressive mechanical behavior of the nanocomposites were investigated. The results of mechanical tests showed that the porous systems with the addition of 1 wt.% of organoclay (OMNIT) exhibited a 90% and 50% increase of collapse stress and elastic modulus values, respectively, as compared to neat porous PMMA. (c) 2006 Elsevier Ltd. All rights reserved. |
2006 |
Akkas, Deniz H; Ovecoglu, Lutfi M; Tanoglu, Metin Silicon oxycarbide-based composites produced from pyrolysis of polysiloxanes with active Ti filler Journal Article JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 26 (15), pp. 3441-3449, 2006, ISSN: 0955-2219. @article{ISI:000241086000049, title = {Silicon oxycarbide-based composites produced from pyrolysis of polysiloxanes with active Ti filler}, author = {Deniz H Akkas and Lutfi M Ovecoglu and Metin Tanoglu}, doi = {10.1016/j.jeurceramsoc.2005.08.017}, issn = {0955-2219}, year = {2006}, date = {2006-01-01}, journal = {JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, volume = {26}, number = {15}, pages = {3441-3449}, abstract = {Phenyl (PPS) and methyl (PMS) containing polysiloxanes were pyrolyzed at elevated temperatures (900-1500 degrees C) under argon atmosphere to investigate the phase developments within the polymers. It was found that pyrolysis of the polymers under inert atmosphere up to 1300 degrees C leads to amorphous silicon oxycarbide (SiOxCy) ceramics. Conversions at higher temperatures results in the transformations into the crystalline beta-SiC phases. Ceramic matrix composites (CMCs) were developed based on the active filler controlled pyrolysis (AFCOP) of polysiloxanes with active Ti filler additions. CMC monoliths were prepared with 60-80 wt.% of active Ti particulates blended into polymer precursors. Green bodies of the composites were made by warm pressing under 15 MPa pressure and ceramics were obtained by pyrolysis at elevated temperatures between 900 and 1500 degrees C under argon atmosphere. The results showed that due to the incorporation of active Ti fillers, formation of crystalline phases such as TiC, TiSi, and TiO occured within the amorphous matrix due to the reactions between the Ti and the polymer decomposition products. The microstructural and mechanical characterization results of the composites are presented within the paper. (c) 2005 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Phenyl (PPS) and methyl (PMS) containing polysiloxanes were pyrolyzed at elevated temperatures (900-1500 degrees C) under argon atmosphere to investigate the phase developments within the polymers. It was found that pyrolysis of the polymers under inert atmosphere up to 1300 degrees C leads to amorphous silicon oxycarbide (SiOxCy) ceramics. Conversions at higher temperatures results in the transformations into the crystalline beta-SiC phases. Ceramic matrix composites (CMCs) were developed based on the active filler controlled pyrolysis (AFCOP) of polysiloxanes with active Ti filler additions. CMC monoliths were prepared with 60-80 wt.% of active Ti particulates blended into polymer precursors. Green bodies of the composites were made by warm pressing under 15 MPa pressure and ceramics were obtained by pyrolysis at elevated temperatures between 900 and 1500 degrees C under argon atmosphere. The results showed that due to the incorporation of active Ti fillers, formation of crystalline phases such as TiC, TiSi, and TiO occured within the amorphous matrix due to the reactions between the Ti and the polymer decomposition products. The microstructural and mechanical characterization results of the composites are presented within the paper. (c) 2005 Elsevier Ltd. All rights reserved. |
0000 |
Ç, Erdal ; Öztoprak, Funda; ğ, Faruk Ebeo M; i, I{ş}; ğ, Recep Yi; ğ, Metin Tano; Aslan, Hasan; others, Synthesis, characterization and optical properties of ZnO-CuO-Al2O3 semiconducting films on glass substrates by sol-gel technique Journal Article Usak University Journal of Material Sciences, 1 (2), pp. 147–172, 0000. @article{ccelik1synthesis, title = {Synthesis, characterization and optical properties of ZnO-CuO-Al2O3 semiconducting films on glass substrates by sol-gel technique}, author = {Erdal {Ç}elik and Funda Öztoprak and Faruk M Ebeo{ğ}lugil and I{ş}{i}l Birlik and Recep Yi{ğ}it and Metin Tano{ğ}lu and Hasan Aslan and others}, journal = {Usak University Journal of Material Sciences}, volume = {1}, number = {2}, pages = {147--172}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Prof. Dr. Alper Taşdemirci
Educational Background
B.Sc. Erciyes University, Turkey, Mechanical Engineering, 1998
M.Sc. Erciyes University, Turkey, Mechanical Engineering, 2000
Ph.D. University of Delaware, USA, Mechanical Engineering, 2005
Research Interests
- Static and Dynamic Mechanical Behaviors of materials
- High Strain Rate Testing Methods: Split Hopkinson Pressure Bar
- Drop Weight Test, Dynamic Response and Constitutive Modelling of Materials
- Experimental and Computational Mechanics, Composite Armor Mechanics
- +90 232 750 6780
- +90 232 750 6701
- Mechanical Engineering Building (Z11)
Publications
2024 |
Movahedi, Nima; Fiedler, Thomas; Sarıkaya, Mustafa; Taşdemirci, Alper; Murch, Graeme E; Belova, Irina V; Güden, Mustafa Dynamic Compression of Metal Syntactic Foam-Filled Aluminum Tubes Journal Article 2024. @article{Movahedi2024b, title = {Dynamic Compression of Metal Syntactic Foam-Filled Aluminum Tubes}, author = {Nima Movahedi and Thomas Fiedler and Mustafa Sarıkaya and Alper Taşdemirci and Graeme E Murch and Irina V Belova and Mustafa Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85198745483&doi=10.1007%2fs11665-024-09825-5&partnerID=40&md5=4df9e4a30678b89ad11b1d1af85ba212}, doi = {10.1007/s11665-024-09825-5}, year = {2024}, date = {2024-01-01}, abstract = {The current research investigates the compressive properties of metal syntactic foam (MSF)-filled tubes at dynamic loads with an impact velocity of 4 m/s. For this purpose, A356 aluminum alloy syntactic foams were prepared using an infiltration casting technique with an incorporation of expanded perlite (EP) filler particles. The study involves the testing and comparison of both MSF samples and MSF-filled tubes under dynamic loading scenarios. In the case of MSF-filled tubes, aluminum tubes are either fully filled (FFT) or half-filled (HFT) with MSFs. The manufactured foams and foam cores have a similar macroscopic density across all tested samples. Under dynamic loading, the MSF, HFT, and FFT samples exhibit distinct and different deformation mechanisms. In MSFs, dynamic compression is controlled by shearing of the sample, whereas in HFTs and FFTs, dynamic deformation occurs through the folding and buckling of the tubes, accompanied by partial deformation of the MSF cores. © ASM International 2024.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The current research investigates the compressive properties of metal syntactic foam (MSF)-filled tubes at dynamic loads with an impact velocity of 4 m/s. For this purpose, A356 aluminum alloy syntactic foams were prepared using an infiltration casting technique with an incorporation of expanded perlite (EP) filler particles. The study involves the testing and comparison of both MSF samples and MSF-filled tubes under dynamic loading scenarios. In the case of MSF-filled tubes, aluminum tubes are either fully filled (FFT) or half-filled (HFT) with MSFs. The manufactured foams and foam cores have a similar macroscopic density across all tested samples. Under dynamic loading, the MSF, HFT, and FFT samples exhibit distinct and different deformation mechanisms. In MSFs, dynamic compression is controlled by shearing of the sample, whereas in HFTs and FFTs, dynamic deformation occurs through the folding and buckling of the tubes, accompanied by partial deformation of the MSF cores. © ASM International 2024. |
2023 |
Enser, Samed; Guden, Mustafa; Tasdemirci, Alper; Davut, Kemal The strain rate history effect in a selective-laser-melt 316L stainless steel Journal Article MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 862 , 2023. @article{WOS:000905147200003, title = {The strain rate history effect in a selective-laser-melt 316L stainless steel}, author = {Samed Enser and Mustafa Guden and Alper Tasdemirci and Kemal Davut}, doi = {10.1016/j.msea.2022.144439}, year = {2023}, date = {2023-01-01}, journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, volume = {862}, abstract = {The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. |
Güden, Mustafa; Riaz, Arslan Bin; Toksoy, Ahmet Kaan; Yıldıztekin, Murat; Erten, Hacer İrem; Çimen, Gülden; Hızlı, Burak; Çellek, Burçin Seven; Güleç, Efe; Taşdemirci, Alper; Yavaş, Hakan; Altınok, Sertaç Materials Science and Engineering: A, 885 , 2023. @article{Güden2023b, title = {Investigation and validation of the flow stress equation and damage model parameters of an electron beam melted Ti6Al4V alloy with a martensitic phase}, author = {Mustafa Güden and Arslan Bin Riaz and Ahmet Kaan Toksoy and Murat Yıldıztekin and Hacer İrem Erten and Gülden Çimen and Burak Hızlı and Burçin Seven Çellek and Efe Güleç and Alper Taşdemirci and Hakan Yavaş and Sertaç Altınok}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85171624739&doi=10.1016%2fj.msea.2023.145590&partnerID=40&md5=206e908384653029d335d5611a983306}, doi = {10.1016/j.msea.2023.145590}, year = {2023}, date = {2023-01-01}, journal = {Materials Science and Engineering: A}, volume = {885}, abstract = {The Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of α' (martensite) and α+β and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of α′ phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post-peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain. © 2023 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Johnson and Cook flow stress and damage model parameters of an electron beam melt (EBM)-Ti64 alloy composed of α' (martensite) and α+β and an extruded-annealed conventional Ti64 alloy were determined experimentally. The validities of the determined flow stress equations and damage model parameters were then verified by the numerical simulations of the compression tests on the Body Centered Cubic lattices produced using the same EBM parameters with the solid EBM samples. In addition, a compression flow stress equation was extracted from the small-size test specimens (1 and 2 mm diameter) taken directly from the struts of the as-built lattices. The microscopic observations, XRD analyses and hardness tests confirmed the presence of α′ phase in the EBM solid samples and in the struts of the BCC lattices, which reduced the ductility of the EBM solid specimens and struts compared to the conventional Ti64. Furthermore, the partially melt particles on the surfaces of the struts acted as the stress concentration sides for micro-cracking; hence, the compression flow stresses of the struts were found to be significantly lower than those of the as-built EBM solid specimens. The flow stress equation derived from the struts predicted more accurately the compression behavior of the lattices. The compression tests and models showed that early damage formation in the lattices was noted to decrease the initial peak and post-peak stresses. As with the experiments, the initial damage occurred in the models with the separation of the nodes at the lattice cell surface edges. This resulted in an abrupt reduction in the stresses after the peak stress. The numerical lattices without damage showed a localized lattice deformation at the mid-sections and the stress increased continuously as a function of normal strain. © 2023 Elsevier B.V. |
Çelik, Muhammet; Güden, Mustafa; Sarıkaya, Mustafa; Taşdemirci, Alper; Genç, Cem; Ersoy, Kurtuluş; Serin, Özgür Composite Structures, 320 , 2023. @article{Çelik2023, title = {The impact response of a Nomex® honeycomb core/E-glass/epoxy composite sandwich structure to increasing velocities: Experimental and numerical analysis}, author = {Muhammet Çelik and Mustafa Güden and Mustafa Sarıkaya and Alper Taşdemirci and Cem Genç and Kurtuluş Ersoy and Özgür Serin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162005169&doi=10.1016%2fj.compstruct.2023.117205&partnerID=40&md5=fb47471b22e7653bc2d670c7a45b347b}, doi = {10.1016/j.compstruct.2023.117205}, year = {2023}, date = {2023-01-01}, journal = {Composite Structures}, volume = {320}, abstract = {The impact response of an E-glass fiber reinforced epoxy/Nomex® honeycomb core sandwich was investigated both experimentally and numerically at increasing velocities through concentrated quasi-static indentation force (CQIF), low velocity impact (LVI) and high velocity impact (HVI) tests. The composite face sheets and core were modelled using MAT_162 and MAT_026 homogenized material model in LS-DYNA, respectively. The experimental and numerical LVI test forces corresponding to core crushing and face sheet penetration were shown to be higher than those of the CQIF tests and increased as the impactor velocity increased. The increase of the impact forces at increasing velocities was largely ascribed to the inertia and the strain rate sensitive fracture strength of the composite sheets. The core shearing was detected in the CQIF and LVI tests both experimentally and numerically. It was also detected in the HVI tests at the velocities less than 20 m s−1. The deformation in the HVI tests at and above ∼ 29.4 m s−1 was highly localized in the impact area with no core shearing and a large delamination damage area at the front face sheet. The force enhancement due to the micro-inertia of the core deformation was shown to be not significant at the studied velocities. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The impact response of an E-glass fiber reinforced epoxy/Nomex® honeycomb core sandwich was investigated both experimentally and numerically at increasing velocities through concentrated quasi-static indentation force (CQIF), low velocity impact (LVI) and high velocity impact (HVI) tests. The composite face sheets and core were modelled using MAT_162 and MAT_026 homogenized material model in LS-DYNA, respectively. The experimental and numerical LVI test forces corresponding to core crushing and face sheet penetration were shown to be higher than those of the CQIF tests and increased as the impactor velocity increased. The increase of the impact forces at increasing velocities was largely ascribed to the inertia and the strain rate sensitive fracture strength of the composite sheets. The core shearing was detected in the CQIF and LVI tests both experimentally and numerically. It was also detected in the HVI tests at the velocities less than 20 m s−1. The deformation in the HVI tests at and above ∼ 29.4 m s−1 was highly localized in the impact area with no core shearing and a large delamination damage area at the front face sheet. The force enhancement due to the micro-inertia of the core deformation was shown to be not significant at the studied velocities. © 2023 Elsevier Ltd |
Sarıkaya, Mustafa; Güden, Mustafa; Kambur, Çağdaş; Özbek, Sevim Çankaya; Taşdemirci, Alper Development of the Johnson-Cook flow stress and damage parameters for the impact response of polycarbonate: Experimental and numerical approach Journal Article International Journal of Impact Engineering, 179 , 2023. @article{Sarıkaya2023, title = {Development of the Johnson-Cook flow stress and damage parameters for the impact response of polycarbonate: Experimental and numerical approach}, author = {Mustafa Sarıkaya and Mustafa Güden and Çağdaş Kambur and Sevim Çankaya Özbek and Alper Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85160689008&doi=10.1016%2fj.ijimpeng.2023.104674&partnerID=40&md5=26109d206458c5db0dfc878ae314e9b4}, doi = {10.1016/j.ijimpeng.2023.104674}, year = {2023}, date = {2023-01-01}, journal = {International Journal of Impact Engineering}, volume = {179}, abstract = {The Johnson and Cook (JC) flow stress and damage model parameters of a polycarbonate (PC) plate were determined by the mechanical tests and numerical simulations of the tests. The experimental tests included quasi-static and high strain rate tension and compression, quasi-static notched-specimen tension, quasi-static indentation (QSI), low velocity impact (LVI) and projectile impact (PI). Initially, five different quasi-static flow stress-strain equations were extracted from the experimental and numerical tests. The flow stress equation determined from the experimental average true stress-true strain curve well agreed with the effective stress-strain obtained from the quasi-static numerical tension test. The numerical QSI force-displacement curve based on the experimental average true stress-true strain equation was further shown to be very similar to that of the experiment. The LVI and PI test simulations were then continued with the experimental average true stress-true strain equation using five different flow stress-strain rate relations: JC, Huh and Kang (HK), Allen-Rule and Jones (ARJ), Cowper-Symonds (CS) and the nonlinear rate approach (NLA). The rate sensitivity parameters of these relations were extracted from the quasi-static and high strain rate tests. The LVI test simulations using the stress-strain rate relations exhibited force-displacement curves higher than those of the experiments. The detected almost no strain rate sensitivity in the LVI tests was ascribed to low strain rate dependency of the flow stress at these intermediate strain rates and large strains involved. On the other side, all the stress-strain rate relations investigated nearly predicted the experimental damage types: dishing at 100 and 140 m s−1 and petalling at 160 m s−1, except the CS relation which predicted the fracture of the plate at 140 m s−1. The experimental average projectile exit velocity at 160 m s−1 was further well predicted by the used stress-strain rate relations while the experimental average petal thicknesses were under estimated by the models. The absorbed energy at 160 m s−1 PI test was determined 1.6 times that of the QSI test, which proved an increased energy absorption capability of the tested PC at the investigated impact velocities. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The Johnson and Cook (JC) flow stress and damage model parameters of a polycarbonate (PC) plate were determined by the mechanical tests and numerical simulations of the tests. The experimental tests included quasi-static and high strain rate tension and compression, quasi-static notched-specimen tension, quasi-static indentation (QSI), low velocity impact (LVI) and projectile impact (PI). Initially, five different quasi-static flow stress-strain equations were extracted from the experimental and numerical tests. The flow stress equation determined from the experimental average true stress-true strain curve well agreed with the effective stress-strain obtained from the quasi-static numerical tension test. The numerical QSI force-displacement curve based on the experimental average true stress-true strain equation was further shown to be very similar to that of the experiment. The LVI and PI test simulations were then continued with the experimental average true stress-true strain equation using five different flow stress-strain rate relations: JC, Huh and Kang (HK), Allen-Rule and Jones (ARJ), Cowper-Symonds (CS) and the nonlinear rate approach (NLA). The rate sensitivity parameters of these relations were extracted from the quasi-static and high strain rate tests. The LVI test simulations using the stress-strain rate relations exhibited force-displacement curves higher than those of the experiments. The detected almost no strain rate sensitivity in the LVI tests was ascribed to low strain rate dependency of the flow stress at these intermediate strain rates and large strains involved. On the other side, all the stress-strain rate relations investigated nearly predicted the experimental damage types: dishing at 100 and 140 m s−1 and petalling at 160 m s−1, except the CS relation which predicted the fracture of the plate at 140 m s−1. The experimental average projectile exit velocity at 160 m s−1 was further well predicted by the used stress-strain rate relations while the experimental average petal thicknesses were under estimated by the models. The absorbed energy at 160 m s−1 PI test was determined 1.6 times that of the QSI test, which proved an increased energy absorption capability of the tested PC at the investigated impact velocities. © 2023 Elsevier Ltd |
2020 |
Seven, Semih Berk; Cankaya, Alper M; Uysal, Cetin; Tasdemirci, Alper; Saatci, Selcuk; Guden, Mustafa Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete Journal Article STRAIN, 2020, ISSN: 0039-2103. @article{ISI:000605351700001, title = {Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete}, author = {Semih Berk Seven and Alper M Cankaya and Cetin Uysal and Alper Tasdemirci and Selcuk Saatci and Mustafa Guden}, doi = {10.1111/str.12377, Early Access Date = JAN 2021}, issn = {0039-2103}, year = {2020}, date = {2020-00-00}, journal = {STRAIN}, abstract = {The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. |
2017 |
Odac, Ismet Kutlay; Guden, Mustafa; Klcaslan, Cenk; Tasdemirci, Alper The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 103 , pp. 64-75, 2017, ISSN: 0734-743X. @article{ISI:000395844400006, title = {The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling}, author = {Ismet Kutlay Odac and Mustafa Guden and Cenk Klcaslan and Alper Tasdemirci}, doi = {10.1016/j.ijimpeng.2016.10.014}, issn = {0734-743X}, year = {2017}, date = {2017-05-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {103}, pages = {64-75}, abstract = {An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved. |
2016 |
Tasdemirci, Alper; Kara, Ali The effect of perforations on the stress wave propagation characteristics of multilayered materials Journal Article JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS, 29 (12), pp. 1680-1695, 2016, ISSN: 0892-7057. @article{ISI:000390559000007, title = {The effect of perforations on the stress wave propagation characteristics of multilayered materials}, author = {Alper Tasdemirci and Ali Kara}, doi = {10.1177/0892705715584409}, issn = {0892-7057}, year = {2016}, date = {2016-12-01}, journal = {JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS}, volume = {29}, number = {12}, pages = {1680-1695}, abstract = {The effect of perforated interlayers on the stress wave transmission of multilayered materials was investigated both experimentally and numerically using the Split Hopkinson pressure bar (SHPB) testing. The multilayer combinations consisted of a ceramic face plate and a glass/epoxy backing plate with a laterally constrained low modulus solid or perforated rubber and Teflon interlayer. The perforations on rubber interlayer delayed the stress rise time and reduced the magnitude of the transmitted stress wave at low strains, while the perforations allowed the passage of relatively high transmitted stresses at large strains similar to the solid rubber interlayer. It was concluded that the effect of perforations were somewhat less pronounced in Teflon interlayer configuration, arising from its relatively low Poisson's ratio. It was finally shown that SHPB testing accompanied with the numerical simulations can be used to analyze the effect of compliant interlayer insertion in the multilayered structures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of perforated interlayers on the stress wave transmission of multilayered materials was investigated both experimentally and numerically using the Split Hopkinson pressure bar (SHPB) testing. The multilayer combinations consisted of a ceramic face plate and a glass/epoxy backing plate with a laterally constrained low modulus solid or perforated rubber and Teflon interlayer. The perforations on rubber interlayer delayed the stress rise time and reduced the magnitude of the transmitted stress wave at low strains, while the perforations allowed the passage of relatively high transmitted stresses at large strains similar to the solid rubber interlayer. It was concluded that the effect of perforations were somewhat less pronounced in Teflon interlayer configuration, arising from its relatively low Poisson's ratio. It was finally shown that SHPB testing accompanied with the numerical simulations can be used to analyze the effect of compliant interlayer insertion in the multilayered structures. |
Tasdemirci, Alper; Kara, Ali; Turan, Kivanc; Sahin, Selim; Guden, Mustafa Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures Journal Article THIN-WALLED STRUCTURES, 100 , pp. 180-191, 2016, ISSN: 0263-8231. @article{ISI:000369463600016, title = {Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures}, author = {Alper Tasdemirci and Ali Kara and Kivanc Turan and Selim Sahin and Mustafa Guden}, doi = {10.1016/j.tws.2015.12.012}, issn = {0263-8231}, year = {2016}, date = {2016-03-01}, journal = {THIN-WALLED STRUCTURES}, volume = {100}, pages = {180-191}, abstract = {The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved. |
2015 |
Tasdemirci, Alper; Kara, Ali; Turan, Kivanc; Sahin, Selim Dynamic crushing and energy absorption of sandwich structures with combined geometry shell cores Journal Article THIN-WALLED STRUCTURES, 91 , pp. 116-128, 2015, ISSN: 0263-8231. @article{ISI:000352174200011, title = {Dynamic crushing and energy absorption of sandwich structures with combined geometry shell cores}, author = {Alper Tasdemirci and Ali Kara and Kivanc Turan and Selim Sahin}, doi = {10.1016/j.tws.2015.02.015}, issn = {0263-8231}, year = {2015}, date = {2015-06-01}, journal = {THIN-WALLED STRUCTURES}, volume = {91}, pages = {116-128}, abstract = {Dynamic crushing and energy absorption characteristics of sandwich structures with combined geometry shell cores were investigated experimentally and numerically. The effect of strain rate on the crushing behavior was presented by the crushing tests at quasi-static, intermediate and high strain rate regimes. It was shown that absorbed energy increased with increasing impact velocity. The effect of confinement on crushing behavior was shown by conducting confined experiments at quasi-static and dynamic rates. Higher buckling loads at lower deformation were observed in confined quasi-static crushing due to additional lateral support and friction provided by confinement wall. By using fictitious numerical models with strain rate insensitive material models, the effect of inertia and strain rate on crushing were shown. It was observed that, increase in impact velocity caused increase in inertial effects and strain rate effects were nearly independent from the impact velocity. The effects of multilayering were also investigated numerically. (C) 2015 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dynamic crushing and energy absorption characteristics of sandwich structures with combined geometry shell cores were investigated experimentally and numerically. The effect of strain rate on the crushing behavior was presented by the crushing tests at quasi-static, intermediate and high strain rate regimes. It was shown that absorbed energy increased with increasing impact velocity. The effect of confinement on crushing behavior was shown by conducting confined experiments at quasi-static and dynamic rates. Higher buckling loads at lower deformation were observed in confined quasi-static crushing due to additional lateral support and friction provided by confinement wall. By using fictitious numerical models with strain rate insensitive material models, the effect of inertia and strain rate on crushing were shown. It was observed that, increase in impact velocity caused increase in inertial effects and strain rate effects were nearly independent from the impact velocity. The effects of multilayering were also investigated numerically. (C) 2015 Elsevier Ltd. All rights reserved. |
Tasdemirci, Alper; Sahin, Selim; Kara, Ali; Turan, Kivanc THIN-WALLED STRUCTURES, 86 , pp. 83-93, 2015, ISSN: 0263-8231. @article{ISI:000347130100010, title = {Crushing and energy absorption characteristics of combined geometry shells at quasi-static and dynamic strain rates: Experimental and numerical study}, author = {Alper Tasdemirci and Selim Sahin and Ali Kara and Kivanc Turan}, doi = {10.1016/j.tws.2014.09.020}, issn = {0263-8231}, year = {2015}, date = {2015-01-01}, journal = {THIN-WALLED STRUCTURES}, volume = {86}, pages = {83-93}, abstract = {The quasi-static and dynamic crushing response and the energy absorption characteristics of combined geometry shells composed of a hemispherical cap and a cylindrical segment were investigated both experimentally and numerically. The inelastic deformation of the shells initiated with the inversion of the hemisphere cap and followed by the axisymmetric or diamond folding of the cylindrical segment depending on the loading rate and dimensions. The fracture of the thinner specimens in dynamic tests was ascribed to the rise of the flow stress to the fracture stress with increasing strain rate. The hemisphere cap absorbed more energy at dynamic rates than at quasi-static rates, while it exhibited lower strain rate and inertia sensitivities than the cylinder segment. For both the hemisphere cap and the cylinder segment, the inertial effect was shown to be more pronounced than strain rate effect at increasing impact velocities. (C) 2014 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quasi-static and dynamic crushing response and the energy absorption characteristics of combined geometry shells composed of a hemispherical cap and a cylindrical segment were investigated both experimentally and numerically. The inelastic deformation of the shells initiated with the inversion of the hemisphere cap and followed by the axisymmetric or diamond folding of the cylindrical segment depending on the loading rate and dimensions. The fracture of the thinner specimens in dynamic tests was ascribed to the rise of the flow stress to the fracture stress with increasing strain rate. The hemisphere cap absorbed more energy at dynamic rates than at quasi-static rates, while it exhibited lower strain rate and inertia sensitivities than the cylinder segment. For both the hemisphere cap and the cylinder segment, the inertial effect was shown to be more pronounced than strain rate effect at increasing impact velocities. (C) 2014 Elsevier Ltd. All rights reserved. |
2014 |
Demir, Mustafa M; Horzum, Nesrin; Tasdemirci, Alper; Turan, Kivanc; Guden, Mustafa Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix Journal Article ACS APPLIED MATERIALS & INTERFACES, 6 (24), pp. 21901-21905, 2014, ISSN: 1944-8244. @article{ISI:000347139400018, title = {Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix}, author = {Mustafa M Demir and Nesrin Horzum and Alper Tasdemirci and Kivanc Turan and Mustafa Guden}, doi = {10.1021/am507029c}, issn = {1944-8244}, year = {2014}, date = {2014-12-01}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {6}, number = {24}, pages = {21901-21905}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kilicaslan, Cenk; Gueden, Mustafa; Odaci, Ismet Kutlay; Tasdemirci, Alper Experimental and numerical studies on the quasi-static and dynamic crushing responses of multi-layer trapezoidal aluminum corrugated sandwiches Journal Article THIN-WALLED STRUCTURES, 78 , pp. 70-78, 2014, ISSN: 0263-8231. @article{ISI:000335543900007, title = {Experimental and numerical studies on the quasi-static and dynamic crushing responses of multi-layer trapezoidal aluminum corrugated sandwiches}, author = {Cenk Kilicaslan and Mustafa Gueden and Ismet Kutlay Odaci and Alper Tasdemirci}, doi = {10.1016/j.tws.2014.01.017}, issn = {0263-8231}, year = {2014}, date = {2014-05-01}, journal = {THIN-WALLED STRUCTURES}, volume = {78}, pages = {70-78}, abstract = {The axial crushing responses of bonded and brazed multi-layer 1050 H14 trapezoidal aluminum corrugated core (fin) sandwich structures, with and without aluminum interlayer sheets in 0 degrees/0 degrees and 0 degrees/90 degrees core orientations, were both experimentally and numerically investigated at quasi-static and dynamic strain rates. Multi-layering the core layers decreased the buckling stress and increased the densification strain. The experimental and simulation compression stress-strain curves showed reasonable agreements with each other. Two main crushing modes were observed experimentally and numerically: the progressive fin folding and the shearing interlayer aluminum sheets. Both, the simulation and experimental buckling and post-buckling stresses increased when the interlayer sheets were constraint laterally. The multi-layer samples without interlayer sheets in 0 degrees/90 degrees core orientation exhibited higher buckling stresses than the samples in 0 degrees/0 degrees core orientation. The increased buckling stress of 0 degrees/0 degrees oriented core samples without interlayer sheets at high strain rate was attributed to the micro-inertial effects which led to increased bending forces at higher impact velocities. (C) 2014 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The axial crushing responses of bonded and brazed multi-layer 1050 H14 trapezoidal aluminum corrugated core (fin) sandwich structures, with and without aluminum interlayer sheets in 0 degrees/0 degrees and 0 degrees/90 degrees core orientations, were both experimentally and numerically investigated at quasi-static and dynamic strain rates. Multi-layering the core layers decreased the buckling stress and increased the densification strain. The experimental and simulation compression stress-strain curves showed reasonable agreements with each other. Two main crushing modes were observed experimentally and numerically: the progressive fin folding and the shearing interlayer aluminum sheets. Both, the simulation and experimental buckling and post-buckling stresses increased when the interlayer sheets were constraint laterally. The multi-layer samples without interlayer sheets in 0 degrees/90 degrees core orientation exhibited higher buckling stresses than the samples in 0 degrees/0 degrees core orientation. The increased buckling stress of 0 degrees/0 degrees oriented core samples without interlayer sheets at high strain rate was attributed to the micro-inertial effects which led to increased bending forces at higher impact velocities. (C) 2014 Elsevier Ltd. All rights reserved. |
2013 |
Attila, Yigit; Guden, Mustafa; Tasdemirci, Alper Foam glass processing using a polishing glass powder residue Journal Article CERAMICS INTERNATIONAL, 39 (5), pp. 5869-5877, 2013, ISSN: 0272-8842. @article{ISI:000318577600141, title = {Foam glass processing using a polishing glass powder residue}, author = {Yigit Attila and Mustafa Guden and Alper Tasdemirci}, doi = {10.1016/j.ceramint.2012.12.104}, issn = {0272-8842}, year = {2013}, date = {2013-07-01}, journal = {CERAMICS INTERNATIONAL}, volume = {39}, number = {5}, pages = {5869-5877}, abstract = {The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
2012 |
Odaci, Ismet Kutlay; Kilicaslan, Cenk; Tasdemirci, Alper; Guden, Mustafa INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 17 (5), pp. 508-518, 2012, ISSN: 1358-8265. @article{ISI:000308991800004, title = {Projectile impact testing of glass fiber-reinforced composite and layered corrugated aluminium and aluminium foam core sandwich panels: a comparative study}, author = {Ismet Kutlay Odaci and Cenk Kilicaslan and Alper Tasdemirci and Mustafa Guden}, doi = {10.1080/13588265.2012.690215}, issn = {1358-8265}, year = {2012}, date = {2012-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {17}, number = {5}, pages = {508-518}, abstract = {E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate.}, keywords = {}, pubstate = {published}, tppubtype = {article} } E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate. |
2008 |
Tasdemirci, Alper The effect of tube end constraining on the axial crushing behavior of an aluminum tube Journal Article MATERIALS & DESIGN, 29 (10), pp. 1992-2001, 2008, ISSN: 0261-3069. @article{ISI:000258564800014, title = {The effect of tube end constraining on the axial crushing behavior of an aluminum tube}, author = {Alper Tasdemirci}, doi = {10.1016/j.matdes.2008.04.011}, issn = {0261-3069}, year = {2008}, date = {2008-12-01}, journal = {MATERIALS & DESIGN}, volume = {29}, number = {10}, pages = {1992-2001}, abstract = {The effect of various types of end constraining on the deformation and load-displacement behavior of a 3003-H 14 Al tube were experimentally and numerically studied. No effect of single-end constraining of tubes was found. Few conditions of double-end constraining tended to revert the deformation mode to mixed and/or diamond mode of deformation. Double-end constraining of tube ends further resulted in an increase in initial drop-load values, widening the initial overshot region in average load-displacement curves. The agreement between numerical and experimental results showed the capabilities of the used numerical model in order to predict end-condition effects in tubular structures. (C) 2008 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of various types of end constraining on the deformation and load-displacement behavior of a 3003-H 14 Al tube were experimentally and numerically studied. No effect of single-end constraining of tubes was found. Few conditions of double-end constraining tended to revert the deformation mode to mixed and/or diamond mode of deformation. Double-end constraining of tube ends further resulted in an increase in initial drop-load values, widening the initial overshot region in average load-displacement curves. The agreement between numerical and experimental results showed the capabilities of the used numerical model in order to predict end-condition effects in tubular structures. (C) 2008 Elsevier Ltd. All rights reserved. |
Assist. Prof. Dr. Halil Tetik
Educational Background
B.Sc. İzmir Institute of Technology, Turkiye, Mechanical Engineering, 2013
M.Sc. İzmir Institute of Technology, Turkiye, Mechanical Engineering, 2016
Ph.D. Kansas State University, USA, Industrial Engineering, 2022
Research Interests
- Additive Manufacturing
- Advanced Manufacturing Techniques
- Functional Aerogels and Their Applications
- +90 232 750 6781
- +90 232 750 6701
- Mechanical Engineering Building (Z12)
Publications
2024 |
Han, Youngshang; Tetik, Halil; Malakooti, Mohammad H 3D Soft Architectures for Stretchable Thermoelectric Wearables with Electrical Self-Healing and Damage Tolerance Journal Article 36 (49), 2024. @article{Han2024b, title = {3D Soft Architectures for Stretchable Thermoelectric Wearables with Electrical Self-Healing and Damage Tolerance}, author = {Youngshang Han and Halil Tetik and Mohammad H Malakooti}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85202693762&doi=10.1002%2fadma.202407073&partnerID=40&md5=2afebff46d368f607b860a71838d38fc}, doi = {10.1002/adma.202407073}, year = {2024}, date = {2024-01-01}, volume = {36}, number = {49}, abstract = {Flexible thermoelectric devices (TEDs) exhibit adaptability to curved surfaces, holding significant potential for small-scale power generation and thermal management. However, they often compromise stretchability, energy conversion, or robustness, thus limiting their applications. Here, the implementation of 3D soft architectures, multifunctional composites, self-healing liquid metal conductors, and rigid semiconductors is introduced to overcome these challenges. These TEDs are extremely stretchable, functioning at strain levels as high as 230%. Their unique design, verified through multiphysics simulations, results in a considerably high power density of 115.4 µW cm⁻2 at a low-temperature gradient of 10 °C. This is achieved through 3D printing multifunctional elastomers and examining the effects of three distinct thermal insulation infill ratios (0%, 12%, and 100%) on thermoelectric energy conversion and structural integrity. The engineered structure is lighter and effectively maintains the temperature gradient across the thermoelectric semiconductors, thereby resulting in higher output voltage and improved heating and cooling performance. Furthermore, these thermoelectric generators show remarkable damage tolerance, remaining fully functional even after multiple punctures and 2000 stretching cycles at 50% strain. When integrated with a 3D-printed heatsink, they can power wearable sensors, charge batteries, and illuminate LEDs by scavenging body heat at room temperature, demonstrating their application as self-sustainable electronics. © 2024 Wiley-VCH GmbH.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Flexible thermoelectric devices (TEDs) exhibit adaptability to curved surfaces, holding significant potential for small-scale power generation and thermal management. However, they often compromise stretchability, energy conversion, or robustness, thus limiting their applications. Here, the implementation of 3D soft architectures, multifunctional composites, self-healing liquid metal conductors, and rigid semiconductors is introduced to overcome these challenges. These TEDs are extremely stretchable, functioning at strain levels as high as 230%. Their unique design, verified through multiphysics simulations, results in a considerably high power density of 115.4 µW cm⁻2 at a low-temperature gradient of 10 °C. This is achieved through 3D printing multifunctional elastomers and examining the effects of three distinct thermal insulation infill ratios (0%, 12%, and 100%) on thermoelectric energy conversion and structural integrity. The engineered structure is lighter and effectively maintains the temperature gradient across the thermoelectric semiconductors, thereby resulting in higher output voltage and improved heating and cooling performance. Furthermore, these thermoelectric generators show remarkable damage tolerance, remaining fully functional even after multiple punctures and 2000 stretching cycles at 50% strain. When integrated with a 3D-printed heatsink, they can power wearable sensors, charge batteries, and illuminate LEDs by scavenging body heat at room temperature, demonstrating their application as self-sustainable electronics. © 2024 Wiley-VCH GmbH. |
Assist. Prof. Dr. Fatih Toksoy
Educational Background
B.Sc. Sakarya University, Turkey, Metallurgical and Materials Engineering, 2006
M.Sc. Rutgers, The State University of New Jersey, USA, Materials Science & Engineering, 2010
Ph.D. Rutgers, The State University of New Jersey, USA, Materials Science & Engineering, 2014
Research Interests
- Boride and Carbide Materials
- Powder Synthesis & Processing
- Materials Characterization
- Sintering
- Hard Ceramics
- +90 232 750 6794
- +90 232 750 6701
- Mechanical Engineering Building (Z09)
Publications
2025 |
Toksoy, Fatih M; Haber, Richard A Regression analysis of material properties and hardness of dense boron carbide Journal Article INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 2025. @article{WOS:001449360600001, title = {Regression analysis of material properties and hardness of dense boron carbide}, author = {Fatih M Toksoy and Richard A Haber}, doi = {10.1111/ijac.15101}, year = {2025}, date = {2025-03-01}, journal = {INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY}, abstract = {Material properties directly affect the final performance of the produced articles. This study aims to establish a correlation between materials properties and hardness of boron carbide samples. Ten different boron carbide powders were sintered to high densities by spark plasma sintering, and material properties (grain size, density, stoichiometry, and free carbon) were analyzed. Hardness tests were conducted on these samples. All experimental procedures were completed by a single operator, and the same instruments were used for all the samples. Multiple linear regressions using the ordinary least squares method in SPSS were carried out to identify the relationship between hardness and material properties. Analyses showed density is the most dominant property, surpassing any other parameter. Grain size became more dominant at higher densities (>99%) and affected hardness results. Both grain size and density are the result of the starting powder and the densification procedure. This study showed that 80% of the hardness variation can be explained by this model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Material properties directly affect the final performance of the produced articles. This study aims to establish a correlation between materials properties and hardness of boron carbide samples. Ten different boron carbide powders were sintered to high densities by spark plasma sintering, and material properties (grain size, density, stoichiometry, and free carbon) were analyzed. Hardness tests were conducted on these samples. All experimental procedures were completed by a single operator, and the same instruments were used for all the samples. Multiple linear regressions using the ordinary least squares method in SPSS were carried out to identify the relationship between hardness and material properties. Analyses showed density is the most dominant property, surpassing any other parameter. Grain size became more dominant at higher densities (>99%) and affected hardness results. Both grain size and density are the result of the starting powder and the densification procedure. This study showed that 80% of the hardness variation can be explained by this model. |
Toksoy, Muhammet Fatih; Elci, Caner Homogeneity enhancement of oxide additives in boron carbide by precipitation method Journal Article PROCESSING AND APPLICATION OF CERAMICS, 19 (1), pp. 110-116, 2025. @article{WOS:001461830200011, title = {Homogeneity enhancement of oxide additives in boron carbide by precipitation method}, author = {Muhammet Fatih Toksoy and Caner Elci}, year = {2025}, date = {2025-01-01}, journal = {PROCESSING AND APPLICATION OF CERAMICS}, volume = {19}, number = {1}, pages = {110-116}, abstract = {This study aims the use of the precipitation method to enhance the uniformity of oxide additives in boron carbide ceramics. Achieving a homogeneous distribution of additives is critical, as higher additive content tends to degrade the mechanical properties of boron carbide. In this research, yttrium and aluminium hydroxide salts were dispersed and incorporated into boron carbide slurry under highly alkaline conditions. The mixture was aged and subsequently calcined to produce metal oxide layers around the boron carbide particles. The additive-to-boron carbide ratio and calcination conditions were systematically varied and the resulting powders were characterized using SEM, EDX and zeta potential analyses. The precipitation method effectively improved additive dispersion, achieving a uniform distribution. Furthermore, samples processed through precipitation exhibited higher densities compared to conventional benchmark samples.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study aims the use of the precipitation method to enhance the uniformity of oxide additives in boron carbide ceramics. Achieving a homogeneous distribution of additives is critical, as higher additive content tends to degrade the mechanical properties of boron carbide. In this research, yttrium and aluminium hydroxide salts were dispersed and incorporated into boron carbide slurry under highly alkaline conditions. The mixture was aged and subsequently calcined to produce metal oxide layers around the boron carbide particles. The additive-to-boron carbide ratio and calcination conditions were systematically varied and the resulting powders were characterized using SEM, EDX and zeta potential analyses. The precipitation method effectively improved additive dispersion, achieving a uniform distribution. Furthermore, samples processed through precipitation exhibited higher densities compared to conventional benchmark samples. |
2017 |
Ma, Luoning; Xie, Kelvin Y; Toksoy, Muhammet F; Kuwelkar, Kanak; Haber, Richard A; Hemker, Kevin J The effect of Si on the microstructure and mechanical properties of spark plasma sintered boron carbide Journal Article MATERIALS CHARACTERIZATION, 134 , pp. 274-278, 2017, ISSN: 1044-5803. @article{ISI:000419416400031, title = {The effect of Si on the microstructure and mechanical properties of spark plasma sintered boron carbide}, author = {Luoning Ma and Kelvin Y Xie and Muhammet F Toksoy and Kanak Kuwelkar and Richard A Haber and Kevin J Hemker}, doi = {10.1016/j.matchar.2017.11.010}, issn = {1044-5803}, year = {2017}, date = {2017-12-01}, journal = {MATERIALS CHARACTERIZATION}, volume = {134}, pages = {274-278}, abstract = {Fully dense boron carbide discs were achieved by spark plasma sintering boron carbide powders with 10 wt% silicon. The silicon did not diffuse into boron carbide grains to produce a solid solution of Si-doped boron carbide; instead the silicon reacted with impurities in the starting powder to form beta-SiC and borosilicate glass. The resultant new phases facilitated densification of the multiphase ceramic through liquid phase-assisted sintering. The resultant material exhibits improved hardness (34.3 GPa Vikers hardness under 1 kg load) with toughness comparable to both Si-free and commercially available boron carbide.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fully dense boron carbide discs were achieved by spark plasma sintering boron carbide powders with 10 wt% silicon. The silicon did not diffuse into boron carbide grains to produce a solid solution of Si-doped boron carbide; instead the silicon reacted with impurities in the starting powder to form beta-SiC and borosilicate glass. The resultant new phases facilitated densification of the multiphase ceramic through liquid phase-assisted sintering. The resultant material exhibits improved hardness (34.3 GPa Vikers hardness under 1 kg load) with toughness comparable to both Si-free and commercially available boron carbide. |
Toksoy, Muhammet Fatih; Rafaniello, William; Xie, Kelvin Yu; Ma, Luoning; Hemker, Kevin Jude; Haber, Richard Alan Densification and characterization of rapid carbothermal synthesized boron carbide Journal Article INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 14 (3), pp. 443-453, 2017, ISSN: 1546-542X. @article{ISI:000404259000018, title = {Densification and characterization of rapid carbothermal synthesized boron carbide}, author = {Muhammet Fatih Toksoy and William Rafaniello and Kelvin Yu Xie and Luoning Ma and Kevin Jude Hemker and Richard Alan Haber}, doi = {10.1111/ijac.12654}, issn = {1546-542X}, year = {2017}, date = {2017-05-01}, journal = {INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY}, volume = {14}, number = {3}, pages = {443-453}, abstract = {Submicrometer boron carbide powders were synthesized using rapid carbothermal reduction (RCR) method. Synthesized boron carbide powders had smaller particle size, lower free carbon, and high density of twins compared to commercial samples. Powders were sintered using spark plasma sintering at different temperatures and dwell times to compare sintering behavior. Synthesized boron carbide powders reached >99% TD at lower temperature and shorter dwell times compared to commercial powders. Improved microhardness observed in the densified RCR samples was likely caused by the combination of higher purity, better stoichiometry control, finer grain size, and a higher density of twin boundaries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Submicrometer boron carbide powders were synthesized using rapid carbothermal reduction (RCR) method. Synthesized boron carbide powders had smaller particle size, lower free carbon, and high density of twins compared to commercial samples. Powders were sintered using spark plasma sintering at different temperatures and dwell times to compare sintering behavior. Synthesized boron carbide powders reached >99% TD at lower temperature and shorter dwell times compared to commercial powders. Improved microhardness observed in the densified RCR samples was likely caused by the combination of higher purity, better stoichiometry control, finer grain size, and a higher density of twin boundaries. |
2016 |
An, Qi; III, William Goddard A; Xie, Kelvin Y; Sim, Gi-dong; Hemker, Kevin J; Munhollon, Tyler; Toksoy, Fatih M; Haber, Richard A Superstrength through Nanotwinning Journal Article NANO LETTERS, 16 (12), pp. 7573-7579, 2016, ISSN: 1530-6984. @article{ISI:000389963200038, title = {Superstrength through Nanotwinning}, author = {Qi An and William A Goddard III and Kelvin Y Xie and Gi-dong Sim and Kevin J Hemker and Tyler Munhollon and Fatih M Toksoy and Richard A Haber}, doi = {10.1021/acs.nanolett.6b03414}, issn = {1530-6984}, year = {2016}, date = {2016-12-01}, journal = {NANO LETTERS}, volume = {16}, number = {12}, pages = {7573-7579}, abstract = {The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins. We also predict from QM that the indentation strength of nanotwinned B4C is 12% higher than that of the perfect crystal. Further, we validate this effect experimentally, showing that nanotwinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nanotwins due to the directional nature of covalent bonds at the TB.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins. We also predict from QM that the indentation strength of nanotwinned B4C is 12% higher than that of the perfect crystal. Further, we validate this effect experimentally, showing that nanotwinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nanotwins due to the directional nature of covalent bonds at the TB. |
Assist. Prof. Dr. Kasım Toprak
Erasmus Co-Coordinator
Educational Background
B.Sc. Zonguldak Karaelmas University, Turkey, Mechanical Engineering, 2006
M.Sc. Rice University, USA, Mechanical Engineering, 2010
Ph.D. Rice University, USA, Mechanical Engineering, 2014
Research Interests
- Energy Efficiency
- Thermal Energy Storage Systems
- Heat Recovery
- HVAC Systems
- Renewable Energy
- Thermal Analysis of Nanomaterials
- Molecular Dynamics
- Thermophysical Properties
- Heat Transfer Enhancement
- +90 232 750 6761
- +90 232 750 6701
- Mechanical Engineering Building (117)
Publications
2024 |
Toprak, Kasim Genetic algorithm optimization of langevin thermostat and thermal properties of graphene-aluminum nanocomposites: a molecular dynamics Journal Article 32 (8), 2024. @article{Toprak2024, title = {Genetic algorithm optimization of langevin thermostat and thermal properties of graphene-aluminum nanocomposites: a molecular dynamics}, author = {Kasim Toprak}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85205914991&doi=10.1088%2f1361-651X%2fad7bdb&partnerID=40&md5=2b43d177fc957643214ea39e6b5089ad}, doi = {10.1088/1361-651X/ad7bdb}, year = {2024}, date = {2024-01-01}, volume = {32}, number = {8}, abstract = {The thermal properties of a laminated structure of graphene-coated aluminum composite nanomaterial were investigated through non-equilibrium molecular dynamics (NEMD) simulations to address the problem of temperature deviation in the thermostat volume applied. This paper presents a new insight into the best values of timestep and Langevin thermostat damping parameters for each atom in the nanomaterial with different size configurations using the genetic algorithm (GA) method by considering the timestep and thermostat damping parameters for each atom type, as well as the thickness of the nanomaterial, the thermostat, buffer, and heat flow lengths. The initial population results indicate that the thermostat temperature deviation increases with higher thermostat damping coefficients and timestep. However, the deviation decreases significantly with increased heat flow and thermostat lengths. Variations in buffer length and aluminum thickness do not have a significant effect on temperature. The application of a GA for optimization leads to a decrease in thermostat temperature deviation. The optimized parameters resulted in better thermostat temperature deviations when analyzing the temperature, aluminum thickness, and both buffer and thermostat lengths. Additionally, the thermal conductivity of aluminum-graphene nanomaterial decreases with increasing temperature, buffer length, and aluminum thickness, but increases by up to 9.85% with increasing thermostat length. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The thermal properties of a laminated structure of graphene-coated aluminum composite nanomaterial were investigated through non-equilibrium molecular dynamics (NEMD) simulations to address the problem of temperature deviation in the thermostat volume applied. This paper presents a new insight into the best values of timestep and Langevin thermostat damping parameters for each atom in the nanomaterial with different size configurations using the genetic algorithm (GA) method by considering the timestep and thermostat damping parameters for each atom type, as well as the thickness of the nanomaterial, the thermostat, buffer, and heat flow lengths. The initial population results indicate that the thermostat temperature deviation increases with higher thermostat damping coefficients and timestep. However, the deviation decreases significantly with increased heat flow and thermostat lengths. Variations in buffer length and aluminum thickness do not have a significant effect on temperature. The application of a GA for optimization leads to a decrease in thermostat temperature deviation. The optimized parameters resulted in better thermostat temperature deviations when analyzing the temperature, aluminum thickness, and both buffer and thermostat lengths. Additionally, the thermal conductivity of aluminum-graphene nanomaterial decreases with increasing temperature, buffer length, and aluminum thickness, but increases by up to 9.85% with increasing thermostat length. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved. |
Toprak, Kasim 32 (2), 2024. @article{Toprak2024b, title = {Understanding neural network tuned Langevin thermostat effect on predicting thermal conductivity of graphene-coated copper using nonequilibrium molecular dynamics simulations}, author = {Kasim Toprak}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85184001044&doi=10.1088%2f1361-651X%2fad1f45&partnerID=40&md5=11d818e0a3b57cf336b3430b6bc60d4b}, doi = {10.1088/1361-651X/ad1f45}, year = {2024}, date = {2024-01-01}, volume = {32}, number = {2}, abstract = {Copper has always been used in thermoelectric applications due to its extensive properties among metals. However, it requires further improving its heat transport performance at the nanosized applications by supporting another high thermal conductivity material. Herein, copper was coated with graphene, and the neural network fitting was employed for the nonequilibrium molecular dynamics simulations of graphene-coated copper nanomaterials to predict thermal conductivity. The Langevin thermostat that was tuned with a neural network fitting (NNF), which makes up the backbone of deep learning, generated the temperature difference between the two ends of the models. The NNF calibrated the Langevin thermostat damping constants that helped to control the temperatures precisely. The buffer and thermostat lengths were also analyzed, and they have considerable effects on the thermostat temperatures and a significant impact on the thermal conductivity of the graphene-coated copper. Regarding thermal conductivity, the four different shapes of vacancy defect concentrations and their locations in the graphene sheets were further investigated. The vacancy between the thermostats significantly decreases the thermal conductivity; however, the vacancy defect in thermostats does not have a similar effect. When the graphene is placed between two copper blocks, the thermal conductivity decreases drastically, and it continues to drop when the sine wave amplitude on the graphene sheet increases. © 2024 IOP Publishing Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Copper has always been used in thermoelectric applications due to its extensive properties among metals. However, it requires further improving its heat transport performance at the nanosized applications by supporting another high thermal conductivity material. Herein, copper was coated with graphene, and the neural network fitting was employed for the nonequilibrium molecular dynamics simulations of graphene-coated copper nanomaterials to predict thermal conductivity. The Langevin thermostat that was tuned with a neural network fitting (NNF), which makes up the backbone of deep learning, generated the temperature difference between the two ends of the models. The NNF calibrated the Langevin thermostat damping constants that helped to control the temperatures precisely. The buffer and thermostat lengths were also analyzed, and they have considerable effects on the thermostat temperatures and a significant impact on the thermal conductivity of the graphene-coated copper. Regarding thermal conductivity, the four different shapes of vacancy defect concentrations and their locations in the graphene sheets were further investigated. The vacancy between the thermostats significantly decreases the thermal conductivity; however, the vacancy defect in thermostats does not have a similar effect. When the graphene is placed between two copper blocks, the thermal conductivity decreases drastically, and it continues to drop when the sine wave amplitude on the graphene sheet increases. © 2024 IOP Publishing Ltd. |
2023 |
Toprak, Kasim; Bayazitoglu, Yildiz LONGITUDINAL THERMAL CONDUCTIVITY OF Cu-SWCNT CORE-SHELL NANOWIRE: MOLECULAR DYNAMICS SIMULATIONS Journal Article Heat Transfer Research, 54 (4), pp. 77 – 89, 2023. @article{Toprak202377, title = {LONGITUDINAL THERMAL CONDUCTIVITY OF Cu-SWCNT CORE-SHELL NANOWIRE: MOLECULAR DYNAMICS SIMULATIONS}, author = {Kasim Toprak and Yildiz Bayazitoglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85159154476&doi=10.1615%2fHeatTransRes.2022044425&partnerID=40&md5=f5dc57c56947ec56a143fb7cf8346175}, doi = {10.1615/HeatTransRes.2022044425}, year = {2023}, date = {2023-01-01}, journal = {Heat Transfer Research}, volume = {54}, number = {4}, pages = {77 – 89}, abstract = {The phonon thermal conductivity of copper core and armchair single-walled carbon nanotube shell (Cu-SWCNT) coaxial nanostructure is presented using the non-equilibrium molecular dynamics (NEMD) simulations method. The study aims to investigate how the ultrathin Cu nanowire affects the thermal conductivity of Cu-SWCNT. The results have revealed that the thermal conductivity of Cu-SWCNT is more than two orders of magnitude higher than that of the Cu core with the contribution of the SWCNT shell. The influences of length, chirality, defect, and core filling on the thermal conductivity of Cu-SWCNT are studied using the two most used C-C potentials, the AIREBO and Tersoff potentials. The bare SWCNT and Cu-SWCNT simulation results revealed that the thermal conductivity using the AIREBO potential is lower than that of Tersoff. Although the thermal conductivity increases with the length of the coaxial tube, it decreases with the chirality and the filling ratio. Increasing the chirality of SWCNT and the Cu core-filling ratio can boost the core copper's contributions to the thermal conductivity, reducing the overall thermal conductivity. The lengths of the thermostat and buffer regions do not significantly affect the thermal conductivity. In addition, the vacancy concentration in heat flow regions effectively reduces thermal conductivity, whereas the vacancy in the thermostat regions does not have a significant effect. The thermal rectification factor defined as changing the imposed heat flux direction is up to 1.73%for the Cu-SWCNT and 2.63% for the SWCNT. © 2023 by Begell House, Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The phonon thermal conductivity of copper core and armchair single-walled carbon nanotube shell (Cu-SWCNT) coaxial nanostructure is presented using the non-equilibrium molecular dynamics (NEMD) simulations method. The study aims to investigate how the ultrathin Cu nanowire affects the thermal conductivity of Cu-SWCNT. The results have revealed that the thermal conductivity of Cu-SWCNT is more than two orders of magnitude higher than that of the Cu core with the contribution of the SWCNT shell. The influences of length, chirality, defect, and core filling on the thermal conductivity of Cu-SWCNT are studied using the two most used C-C potentials, the AIREBO and Tersoff potentials. The bare SWCNT and Cu-SWCNT simulation results revealed that the thermal conductivity using the AIREBO potential is lower than that of Tersoff. Although the thermal conductivity increases with the length of the coaxial tube, it decreases with the chirality and the filling ratio. Increasing the chirality of SWCNT and the Cu core-filling ratio can boost the core copper's contributions to the thermal conductivity, reducing the overall thermal conductivity. The lengths of the thermostat and buffer regions do not significantly affect the thermal conductivity. In addition, the vacancy concentration in heat flow regions effectively reduces thermal conductivity, whereas the vacancy in the thermostat regions does not have a significant effect. The thermal rectification factor defined as changing the imposed heat flux direction is up to 1.73%for the Cu-SWCNT and 2.63% for the SWCNT. © 2023 by Begell House, Inc. |
2020 |
Toprak, Kasim; Ouedraogo, Kiswendsida Elias Performance Analysis of Thermal Storage Assisted Cooling Tower with Night Cooling Journal Article JOURNAL OF POLYTECHNIC-POLITEKNIK DERGISI, 23 (4), pp. 1027-1035, 2020, ISSN: 1302-0900. @article{ISI:000581901200009, title = {Performance Analysis of Thermal Storage Assisted Cooling Tower with Night Cooling}, author = {Kasim Toprak and Kiswendsida Elias Ouedraogo}, issn = {1302-0900}, year = {2020}, date = {2020-12-01}, journal = {JOURNAL OF POLYTECHNIC-POLITEKNIK DERGISI}, volume = {23}, number = {4}, pages = {1027-1035}, abstract = {As global warming and water scarcity issues continue to grow, it is essential to increase resources efficiency for air conditioners and power plants. In order to increase the efficiency, the systems need to be modified to take the advantages of the low night temperature and thermal storage tanks. In this study, the low night temperature and thermal storage tanks effects on the cooling tower is studied using TRNSYS. Using a chiller operating from 8:00 to 16:00 as a case study, hot water from the condenser is partially stored on daytime and cooled slowly during the night. The storage tank volume is optimized by considering two big tanks and five small tanks. The results show that night cooling reduces cooling water temperature by 5.8 degrees C or 21.8% while the cooling efficiency is increased by 36%. The thermal storage tanks enable to have the low continuous flow rate and help to reduce the fan power by 67.1%. On the storage side, compared to two tanks system, the tanks volume is reduced by 16.5% when 5 tanks are used. In theory this reduction can go up to 50% by increasing the number of tanks and reducing their individual size.}, keywords = {}, pubstate = {published}, tppubtype = {article} } As global warming and water scarcity issues continue to grow, it is essential to increase resources efficiency for air conditioners and power plants. In order to increase the efficiency, the systems need to be modified to take the advantages of the low night temperature and thermal storage tanks. In this study, the low night temperature and thermal storage tanks effects on the cooling tower is studied using TRNSYS. Using a chiller operating from 8:00 to 16:00 as a case study, hot water from the condenser is partially stored on daytime and cooled slowly during the night. The storage tank volume is optimized by considering two big tanks and five small tanks. The results show that night cooling reduces cooling water temperature by 5.8 degrees C or 21.8% while the cooling efficiency is increased by 36%. The thermal storage tanks enable to have the low continuous flow rate and help to reduce the fan power by 67.1%. On the storage side, compared to two tanks system, the tanks volume is reduced by 16.5% when 5 tanks are used. In theory this reduction can go up to 50% by increasing the number of tanks and reducing their individual size. |
2014 |
Toprak, Kasim; Bayazitoglu, Yildiz Interfacial thermal resistance of Cu-SWCNT nanowire in water Journal Article INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 79 , pp. 584-588, 2014, ISSN: 0017-9310. @article{ISI:000343781900056, title = {Interfacial thermal resistance of Cu-SWCNT nanowire in water}, author = {Kasim Toprak and Yildiz Bayazitoglu}, doi = {10.1016/j.ijheatmasstransfer.2014.08.024}, issn = {0017-9310}, year = {2014}, date = {2014-12-01}, journal = {INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, volume = {79}, pages = {584-588}, abstract = {The conduction along the radial direction of CuNW-SWCNT nanocomposite surrounded with water is examined. Due to its simplicity and adaptability, a simple point-charge water model is implemented. Using the Nose-Hoover thermostat, the copper core is kept at a uniform temperature as a heat source, and a circular edge layer of water is kept at a lower temperature as a heat sink in order to impose a radial temperature distribution. The thermal boundary resistance was predicted as 0.1732 x 10(8) m(2) K/W at the interface of CuNW-water, 3.16 x 10(-8) m(2) K/W at the interface of SWCNT-water, and 0.743 x 10(-8) m(2) K/W at the interface of (CuNW-SWCNT)-water. (C) 2014 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The conduction along the radial direction of CuNW-SWCNT nanocomposite surrounded with water is examined. Due to its simplicity and adaptability, a simple point-charge water model is implemented. Using the Nose-Hoover thermostat, the copper core is kept at a uniform temperature as a heat source, and a circular edge layer of water is kept at a lower temperature as a heat sink in order to impose a radial temperature distribution. The thermal boundary resistance was predicted as 0.1732 x 10(8) m(2) K/W at the interface of CuNW-water, 3.16 x 10(-8) m(2) K/W at the interface of SWCNT-water, and 0.743 x 10(-8) m(2) K/W at the interface of (CuNW-SWCNT)-water. (C) 2014 Elsevier Ltd. All rights reserved. |
Assist. Prof. Dr. Benay Uzer Yılmaz
Vice Chair
Educational Background
B.Sc. Koç University, Turkey, Mechanical Engineering, 2013
Ph.D. Koç University, Turkey, Mechanical Engineering, 2017
Research Interests
- Mechanical and Microstructural Design of Metallic Implants
- Additive Manufacturing of Metallic Materials
- Biomimetic Architectures for Functional Biomaterials
- Designing Cell-implant Interface
- +90 232 750 6709
- +90 232 750 6701
- Mechanical Engineering Building (110)
Publications
2020 |
Uzer, B Frontiers in Materials, 7 , 2020. @article{Uzer2020, title = {Modulating the Surface Properties of Metallic Implants and the Response of Breast Cancer Cells by Surface Relief Induced via Bulk Plastic Deformation}, author = {B Uzer}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085159761&doi=10.3389%2ffmats.2020.00099&partnerID=40&md5=74ced050c4b670609a1e8bf00f28b1b7}, doi = {10.3389/fmats.2020.00099}, year = {2020}, date = {2020-01-01}, journal = {Frontiers in Materials}, volume = {7}, abstract = {Micro/nanoscale textured surfaces have presented promising tissue–implant integration via increasing surface roughness, energy, and wettability. Recent studies indicate that surface texture imparted on the metallic implants via surface relief induced with simple bulk plastic deformation methods (e.g., tension or compression tests) does result in enhanced cell response. Considering these recent findings, this study presents a thorough investigation of the effects of surface relief on surface properties of implants and cell adhesion. Experiments are conducted on the samples subjected to interrupted tensile tests up to the plastic strains of 5, 15, 25, and 35%. Main findings from these experiments suggest that, as the plastic deformation level increases up to 35% from the undeformed (control) level, (1) average surface roughness (Ra) increases from 17.58 to 595.29 nm; (2) water contact angle decreases from 84.28 to 58.07°; (3) surface free energy (SFE) increases from 36.06 to 48.89 mJ/m2; and (4) breast cancer cells show 2.4-fold increased number of attachment. Increased surface roughness indicates the distorted topography via surface relief and leads to increased wettability, consistent with Wenzel’s theory. The higher levels of SFE observed were related to high-energy regions provided via activation of strengthening mechanisms, which increased in volume fraction concomitant with plastic deformation. Eventually, the displayed improvements in surface properties have increased the number of breast cancer cell attachments. These findings indicate that surface relief induced upon plastic deformation processes could be utilized in the design of implants for therapeutic or diagnostic purposes through capturing breast cancer cells on the material surface. © Copyright © 2020 Uzer.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Micro/nanoscale textured surfaces have presented promising tissue–implant integration via increasing surface roughness, energy, and wettability. Recent studies indicate that surface texture imparted on the metallic implants via surface relief induced with simple bulk plastic deformation methods (e.g., tension or compression tests) does result in enhanced cell response. Considering these recent findings, this study presents a thorough investigation of the effects of surface relief on surface properties of implants and cell adhesion. Experiments are conducted on the samples subjected to interrupted tensile tests up to the plastic strains of 5, 15, 25, and 35%. Main findings from these experiments suggest that, as the plastic deformation level increases up to 35% from the undeformed (control) level, (1) average surface roughness (Ra) increases from 17.58 to 595.29 nm; (2) water contact angle decreases from 84.28 to 58.07°; (3) surface free energy (SFE) increases from 36.06 to 48.89 mJ/m2; and (4) breast cancer cells show 2.4-fold increased number of attachment. Increased surface roughness indicates the distorted topography via surface relief and leads to increased wettability, consistent with Wenzel’s theory. The higher levels of SFE observed were related to high-energy regions provided via activation of strengthening mechanisms, which increased in volume fraction concomitant with plastic deformation. Eventually, the displayed improvements in surface properties have increased the number of breast cancer cell attachments. These findings indicate that surface relief induced upon plastic deformation processes could be utilized in the design of implants for therapeutic or diagnostic purposes through capturing breast cancer cells on the material surface. © Copyright © 2020 Uzer. |
2018 |
Uzer, B; Picak, S; Liu, J; Jozaghi, T; Canadinc, D; Karaman, I; Chumlyakov, Y I; Kireeva, I On the mechanical response and microstructure evolution of NiCoCr single crystalline medium entropy alloys Journal Article Materials Research Letters, 6 (8), pp. 442-449, 2018. @article{Uzer2018442, title = {On the mechanical response and microstructure evolution of NiCoCr single crystalline medium entropy alloys}, author = {B Uzer and S Picak and J Liu and T Jozaghi and D Canadinc and I Karaman and Y I Chumlyakov and I Kireeva}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048308085&doi=10.1080%2f21663831.2018.1478331&partnerID=40&md5=fdf9a8d03d121110bc0c015c525b5373}, doi = {10.1080/21663831.2018.1478331}, year = {2018}, date = {2018-01-01}, journal = {Materials Research Letters}, volume = {6}, number = {8}, pages = {442-449}, abstract = {Unusual strain hardening response and ductility of NiCoCr equiatomic alloy were investigated through microstructural analysis of [111], [110] and [123] single crystals deformed under tension. Nano-twinning prevailed at, as early as, 4% strain along the [110] orientation, providing a steady work hardening, and thereby a significant ductility. While single slip dominated in the [123] orientation at the early stages of deformation, multiple slip and nanotwinning was prominent in the [111] orientation. Significant dislocation storage capability and resistance to necking due to nanotwinning provided unprecedented ductility to NiCoCr medium entropy alloys, making it superior than quinary variants, and conventional low and medium stacking fault energy steels. IMPACT STATEMENT: A comparison of the current results on the ternary medium entropy alloy single crystals and those previously reported on the quinary and quaternary fcc equiatomic alloys demonstrates that a higher configurational entropy does not necessarily warrant improved mechanical properties. © 2018, © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Unusual strain hardening response and ductility of NiCoCr equiatomic alloy were investigated through microstructural analysis of [111], [110] and [123] single crystals deformed under tension. Nano-twinning prevailed at, as early as, 4% strain along the [110] orientation, providing a steady work hardening, and thereby a significant ductility. While single slip dominated in the [123] orientation at the early stages of deformation, multiple slip and nanotwinning was prominent in the [111] orientation. Significant dislocation storage capability and resistance to necking due to nanotwinning provided unprecedented ductility to NiCoCr medium entropy alloys, making it superior than quinary variants, and conventional low and medium stacking fault energy steels. IMPACT STATEMENT: A comparison of the current results on the ternary medium entropy alloy single crystals and those previously reported on the quinary and quaternary fcc equiatomic alloys demonstrates that a higher configurational entropy does not necessarily warrant improved mechanical properties. © 2018, © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. |
Canadinc, D; Uzer, B; Elmadagli, M; Guner, F Nanotwin Formation in High-Manganese Austenitic Steels Under Explosive Shock Loading Journal Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 49 (4), pp. 1026-1030, 2018. @article{Canadinc20181026, title = {Nanotwin Formation in High-Manganese Austenitic Steels Under Explosive Shock Loading}, author = {D Canadinc and B Uzer and M Elmadagli and F Guner}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041919869&doi=10.1007%2fs11661-018-4510-x&partnerID=40&md5=a874b8da4c563aa0e96e5e788ad81251}, doi = {10.1007/s11661-018-4510-x}, year = {2018}, date = {2018-01-01}, journal = {Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science}, volume = {49}, number = {4}, pages = {1026-1030}, abstract = {The micro-deformation mechanisms active in a high-manganese austenitic steel were investigated upon explosive shock loading. Single system of nanotwins forming within primary twins were shown to govern the deformation despite the elevated temperatures attained during testing. The benefits of nanotwin formation for potential armor materials were demonstrated. © 2018, The Minerals, Metals & Materials Society and ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The micro-deformation mechanisms active in a high-manganese austenitic steel were investigated upon explosive shock loading. Single system of nanotwins forming within primary twins were shown to govern the deformation despite the elevated temperatures attained during testing. The benefits of nanotwin formation for potential armor materials were demonstrated. © 2018, The Minerals, Metals & Materials Society and ASM International. |
Uzer, B; Canadinc, D The effect of plastic deformation on the cell viability and adhesion behavior in metallic implant materials Journal Article Ceramic Transactions, 261 , pp. 187-196, 2018. @article{Uzer2018187, title = {The effect of plastic deformation on the cell viability and adhesion behavior in metallic implant materials}, author = {B Uzer and D Canadinc}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055448117&doi=10.1002%2f9781119423829.ch16&partnerID=40&md5=3e385fa138796826206feff61faaf2f2}, doi = {10.1002/9781119423829.ch16}, year = {2018}, date = {2018-01-01}, journal = {Ceramic Transactions}, volume = {261}, pages = {187-196}, abstract = {The adhesion and spreading behavior, and viability of the brain tumor and fibroblast cells were analyzed on the austenitic 316L stainless steel samples, which were deformed to different strains, promoting varying degrees of plastic deformation activities. Surface characterization and microscopy analyses showed that increasing plastic deformation significantly altered surface topography by the formation of surface extrusions and grooves, which increased the surface roughness. In addition, twinning and slip mechanisms created regions with high surface energy which catalyzed the adhesion of tCM proteins and formation of focal contacts. Specifically, tumor cells exhibited a greater viability and adhesion behavior on the samples deformed to the largest plastic strains concomitant with the filopodial extensions, which showed the higher affinity of these cells on the deformed samples. Conversely, fibroblast cells did not exhibit enhanced cell response on the deformed samples, which can stem from the surface roughness, size of the cells or the failure of the adhesion of tCM molecules expressed by the fibroblast cells. The current results show that surface and microstructural properties of the implants can be tailored by the activation of plastic deformation mechanisms to obtain ideal materials specific to body location and treatment. © 2017 The American Ceramic Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The adhesion and spreading behavior, and viability of the brain tumor and fibroblast cells were analyzed on the austenitic 316L stainless steel samples, which were deformed to different strains, promoting varying degrees of plastic deformation activities. Surface characterization and microscopy analyses showed that increasing plastic deformation significantly altered surface topography by the formation of surface extrusions and grooves, which increased the surface roughness. In addition, twinning and slip mechanisms created regions with high surface energy which catalyzed the adhesion of tCM proteins and formation of focal contacts. Specifically, tumor cells exhibited a greater viability and adhesion behavior on the samples deformed to the largest plastic strains concomitant with the filopodial extensions, which showed the higher affinity of these cells on the deformed samples. Conversely, fibroblast cells did not exhibit enhanced cell response on the deformed samples, which can stem from the surface roughness, size of the cells or the failure of the adhesion of tCM molecules expressed by the fibroblast cells. The current results show that surface and microstructural properties of the implants can be tailored by the activation of plastic deformation mechanisms to obtain ideal materials specific to body location and treatment. © 2017 The American Ceramic Society. |
2017 |
Uzer, B; Birer, O; Canadinc, D Investigation of the Dissolution–Reformation Cycle of the Passive Oxide Layer on NiTi Orthodontic Archwires Journal Article Shape Memory and Superelasticity, 3 (3), pp. 264-273, 2017. @article{Uzer2017264, title = {Investigation of the Dissolution–Reformation Cycle of the Passive Oxide Layer on NiTi Orthodontic Archwires}, author = {B Uzer and O Birer and D Canadinc}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070886170&doi=10.1007%2fs40830-017-0114-3&partnerID=40&md5=c157896a2009c27ea7f0b8b4c8b5c33c}, doi = {10.1007/s40830-017-0114-3}, year = {2017}, date = {2017-01-01}, journal = {Shape Memory and Superelasticity}, volume = {3}, number = {3}, pages = {264-273}, abstract = {Dissolution–reformation cycle of the passive oxide layer on the nickel–titanium (NiTi) orthodontic archwires was investigated, which has recently been recognized as one of the key parameters dictating the biocompatibility of archwires. Specifically, commercially available NiTi orthodontic archwires were immersed in artificial saliva solutions of different pH values (2.3, 3.3, and 4.3) for four different immersion periods: 1, 7, 14, and 30 days. Characterization of the virgin and tested samples revealed that the titanium oxide layer on the NiTi archwire surfaces exhibit a dissolution–reformation cycle within the first 14 days of the immersion period: the largest amount of Ni ion release occurred within the first week of immersion, while it significantly decreased during the reformation period from day 7 to day 14. Furthermore, the oxide layer reformation was catalyzed on the grooves within the peaks and valleys due to relatively larger surface energy of these regions, which eventually decreased the surface roughness significantly within the reformation period. Overall, the current results clearly demonstrate that the analyses of dissolution–reformation cycle of the oxide layer in orthodontic archwires, surface roughness, and ion release behavior constitute utmost importance in order to ensure both the highest degree of biocompatibility and an efficient medical treatment. © 2017, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dissolution–reformation cycle of the passive oxide layer on the nickel–titanium (NiTi) orthodontic archwires was investigated, which has recently been recognized as one of the key parameters dictating the biocompatibility of archwires. Specifically, commercially available NiTi orthodontic archwires were immersed in artificial saliva solutions of different pH values (2.3, 3.3, and 4.3) for four different immersion periods: 1, 7, 14, and 30 days. Characterization of the virgin and tested samples revealed that the titanium oxide layer on the NiTi archwire surfaces exhibit a dissolution–reformation cycle within the first 14 days of the immersion period: the largest amount of Ni ion release occurred within the first week of immersion, while it significantly decreased during the reformation period from day 7 to day 14. Furthermore, the oxide layer reformation was catalyzed on the grooves within the peaks and valleys due to relatively larger surface energy of these regions, which eventually decreased the surface roughness significantly within the reformation period. Overall, the current results clearly demonstrate that the analyses of dissolution–reformation cycle of the oxide layer in orthodontic archwires, surface roughness, and ion release behavior constitute utmost importance in order to ensure both the highest degree of biocompatibility and an efficient medical treatment. © 2017, ASM International. |
2016 |
Uzer, B; Toker, S M; Cingoz, A; Bagci-Onder, T; Gerstein, G; Maier, H J; Canadinc, D An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials Journal Article Journal of the Mechanical Behavior of Biomedical Materials, 60 , pp. 177-186, 2016. @article{Uzer2016177, title = {An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials}, author = {B Uzer and S M Toker and A Cingoz and T Bagci-Onder and G Gerstein and H J Maier and D Canadinc}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955118639&doi=10.1016%2fj.jmbbm.2016.01.001&partnerID=40&md5=93dcdcf6f5350d917e906984b75d9693}, doi = {10.1016/j.jmbbm.2016.01.001}, year = {2016}, date = {2016-01-01}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {60}, pages = {177-186}, abstract = {The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining. © 2016 Elsevier Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining. © 2016 Elsevier Ltd. |