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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. |
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. |
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. |
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. |
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 |
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 |
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. |
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. |
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. |
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. |
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. |
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. |
Naseri, F; Gil, S; Barbu, C; Cetkin, E; Yarimca, G; Jensen, A C; Larsen, P G; Gomes, C Digital twin of electric vehicle battery systems: Comprehensive review of the use cases, requirements, and platforms Journal Article Renewable and Sustainable Energy Reviews, 179 , 2023, (All Open Access, Green Open Access, Hybrid Gold Open Access). @article{Naseri2023, title = {Digital twin of electric vehicle battery systems: Comprehensive review of the use cases, requirements, and platforms}, author = {F Naseri and S Gil and C Barbu and E Cetkin and G Yarimca and A C Jensen and P G Larsen and C Gomes}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85152416376&doi=10.1016%2fj.rser.2023.113280&partnerID=40&md5=cecb165a2389d2006c18cb72ba49eb6e}, doi = {10.1016/j.rser.2023.113280}, year = {2023}, date = {2023-01-01}, journal = {Renewable and Sustainable Energy Reviews}, volume = {179}, abstract = {Transportation electrification has been fueled by recent advancements in the technology and manufacturing of battery systems, but the industry yet is facing serious challenges that could be addressed using cutting-edge digital technologies. One such novel technology is based on the digital twining of battery systems. Digital twins (DTs) of batteries utilize advanced multi-layer models, artificial intelligence, advanced sensing units, Internet-of-Things technologies, and cloud computing techniques to provide a virtual live representation of the real battery system (the physical twin) to improve the performance, safety, and cost-effectiveness. Furthermore, they orchestrate the operation of the entire battery value chain offering great advantages, such as improving the economy of manufacturing, re-purposing, and recycling processes. In this context, various studies have been carried out discussing the DT applications and use cases from cloud-enabled battery management systems to the digitalization of battery testing. This work provides a comprehensive review of different possible use cases, key enabling technologies, and requirements for battery DTs. The review inclusively discusses the use cases, development/integration platforms, as well as hardware and software requirements for implementation of the battery DTs, including electrical topics related to the modeling and algorithmic approaches, software architectures, and digital platforms for DT development and integration. The existing challenges are identified and circumstances that will create enough value to justify these challenges, such as the added costs, are discussed. © 2023 The Authors}, note = {All Open Access, Green Open Access, Hybrid Gold Open Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Transportation electrification has been fueled by recent advancements in the technology and manufacturing of battery systems, but the industry yet is facing serious challenges that could be addressed using cutting-edge digital technologies. One such novel technology is based on the digital twining of battery systems. Digital twins (DTs) of batteries utilize advanced multi-layer models, artificial intelligence, advanced sensing units, Internet-of-Things technologies, and cloud computing techniques to provide a virtual live representation of the real battery system (the physical twin) to improve the performance, safety, and cost-effectiveness. Furthermore, they orchestrate the operation of the entire battery value chain offering great advantages, such as improving the economy of manufacturing, re-purposing, and recycling processes. In this context, various studies have been carried out discussing the DT applications and use cases from cloud-enabled battery management systems to the digitalization of battery testing. This work provides a comprehensive review of different possible use cases, key enabling technologies, and requirements for battery DTs. The review inclusively discusses the use cases, development/integration platforms, as well as hardware and software requirements for implementation of the battery DTs, including electrical topics related to the modeling and algorithmic approaches, software architectures, and digital platforms for DT development and integration. The existing challenges are identified and circumstances that will create enough value to justify these challenges, such as the added costs, are discussed. © 2023 The Authors |
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 |
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 |
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 |
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. |
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. |
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. |
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. |
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. |
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. |
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. |
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. © |
Şahin, O N; Dede, M İ C Model-based detection and isolation of the wheel slippage and actuator faults of a holonomic mobile robot Journal Article Industrial Robot, 49 (6), pp. 1202-1217, 2022. @article{Şahin20221202, title = {Model-based detection and isolation of the wheel slippage and actuator faults of a holonomic mobile robot}, author = {O N Şahin and M İ C Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130240953&doi=10.1108%2fIR-01-2022-0001&partnerID=40&md5=bfe89d019e1f0a22ac5484fcb26a7655}, doi = {10.1108/IR-01-2022-0001}, year = {2022}, date = {2022-01-01}, journal = {Industrial Robot}, volume = {49}, number = {6}, pages = {1202-1217}, abstract = {Purpose: Mobile robots may perform very critical tasks under difficult operating conditions. Faults encountered during their tasks may cause the task to be interrupted or failed completely. In the active fault tolerant control methods, it is very important not only to detect the faults that occur in the robot, but also to isolate these faults to develop a fault recovery strategy that is suitable for that specific type of fault. This study aims to develop a model-based fault detection and isolation method for wheel slippage and motor performance degradation that may occur in wheeled mobile robots. Design/methodology/approach: In the proposed method, wheel speeds can be estimated via the dynamic model of the mobile robot, which includes a friction model between the wheel and the ground. Four residual signals are obtained from the differences between the estimated states and the measured states of the mobile robot. Mobile robot’s faults are detected by using these signals. Also, two different residual signals are generated from the calculation of the traction forces with two different procedures. These six residual signals are then used to isolate possible wheel slippage and performance degradation in a motor. Findings: The proposed method for diagnosing wheel slip and performance degradation in motors are tested by moving the robot in various directions. According to the data obtained from the test results, a logic table is created to isolate these two faults from each other. Thanks to the created logic table, slippage in any wheel and performance degradation in any motor can be detected and isolated. Originality/value: Two different recovery strategies are needed to recover temporary wheel slippage and permanent motor faults. Therefore, it is important to isolate these two faults that create similar symptoms in robot’s general movement. Thanks to the method proposed in this study, it is not only possible to isolate the slipping wheel with respect to the non-slipping wheels or to isolate the faulty motor from the non-faulty ones, but also to isolate these two different fault types from each other. © 2022, Emerald Publishing Limited.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Purpose: Mobile robots may perform very critical tasks under difficult operating conditions. Faults encountered during their tasks may cause the task to be interrupted or failed completely. In the active fault tolerant control methods, it is very important not only to detect the faults that occur in the robot, but also to isolate these faults to develop a fault recovery strategy that is suitable for that specific type of fault. This study aims to develop a model-based fault detection and isolation method for wheel slippage and motor performance degradation that may occur in wheeled mobile robots. Design/methodology/approach: In the proposed method, wheel speeds can be estimated via the dynamic model of the mobile robot, which includes a friction model between the wheel and the ground. Four residual signals are obtained from the differences between the estimated states and the measured states of the mobile robot. Mobile robot’s faults are detected by using these signals. Also, two different residual signals are generated from the calculation of the traction forces with two different procedures. These six residual signals are then used to isolate possible wheel slippage and performance degradation in a motor. Findings: The proposed method for diagnosing wheel slip and performance degradation in motors are tested by moving the robot in various directions. According to the data obtained from the test results, a logic table is created to isolate these two faults from each other. Thanks to the created logic table, slippage in any wheel and performance degradation in any motor can be detected and isolated. Originality/value: Two different recovery strategies are needed to recover temporary wheel slippage and permanent motor faults. Therefore, it is important to isolate these two faults that create similar symptoms in robot’s general movement. Thanks to the method proposed in this study, it is not only possible to isolate the slipping wheel with respect to the non-slipping wheels or to isolate the faulty motor from the non-faulty ones, but also to isolate these two different fault types from each other. © 2022, Emerald Publishing Limited. |
Kanlk, M; Ayit, O; Dede, M I C; Tatlicioglu, E Robotica, 40 (7), pp. 2112-2127, 2022. @article{Kanlk20222112, title = {Toward safe and high-performance human-robot collaboration via implementation of redundancy and understanding the effects of admittance term parameters}, author = {M Kanlk and O Ayit and M I C Dede and E Tatlicioglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85119673140&doi=10.1017%2fS0263574721001569&partnerID=40&md5=97f95f7fba03b5aece75e8580f8a1977}, doi = {10.1017/S0263574721001569}, year = {2022}, date = {2022-01-01}, journal = {Robotica}, volume = {40}, number = {7}, pages = {2112-2127}, abstract = {Today, demandsin industrial manufacturing mandate humans to work with large-scale industrial robots, and this collaboration may result in dangerous conditions for humans. To deal with this situation, this work proposes a novel approach for redundant large-scale industrial robots. In the proposed approach, an admittance controller is designed to regulate the interaction between the end effector of the robot and the human. Additionally, an obstacle avoidance algorithm is implemented in the null space of the robot to prevent any possible unexpected collision between the human and the links of the robot. After safety performance of this approach is verified via simulations and experimental studies, the effect of the parameters of the admittance controller on the performance of collaboration in terms of both accuracy and total human effort is investigated. This investigation is carried out via 8 experiments by the participation of 10 test subjects in which the effect of different admittance controller parameters such as mass and damper are compared. As a result of this investigation, tuning insights for such parameters are revealed. © 2021 The Author(s). Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Today, demandsin industrial manufacturing mandate humans to work with large-scale industrial robots, and this collaboration may result in dangerous conditions for humans. To deal with this situation, this work proposes a novel approach for redundant large-scale industrial robots. In the proposed approach, an admittance controller is designed to regulate the interaction between the end effector of the robot and the human. Additionally, an obstacle avoidance algorithm is implemented in the null space of the robot to prevent any possible unexpected collision between the human and the links of the robot. After safety performance of this approach is verified via simulations and experimental studies, the effect of the parameters of the admittance controller on the performance of collaboration in terms of both accuracy and total human effort is investigated. This investigation is carried out via 8 experiments by the participation of 10 test subjects in which the effect of different admittance controller parameters such as mass and damper are compared. As a result of this investigation, tuning insights for such parameters are revealed. © 2021 The Author(s). Published by Cambridge University Press. |
Maaroof, O W; Dede, M İ C; Aydin, L A Robot Arm Design Optimization Method by Using a Kinematic Redundancy Resolution Technique Journal Article Robotics, 11 (1), 2022. @article{Maaroof2022, title = {A Robot Arm Design Optimization Method by Using a Kinematic Redundancy Resolution Technique}, author = {O W Maaroof and M İ C Dede and L Aydin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85122955998&doi=10.3390%2frobotics11010001&partnerID=40&md5=88885649cc03fbdcd72af784eae80615}, doi = {10.3390/robotics11010001}, year = {2022}, date = {2022-01-01}, journal = {Robotics}, volume = {11}, number = {1}, abstract = {Redundancy resolution techniques have been widely used for the control of kinematically redundant robots. In this work, one of the redundancy resolution techniques is employed in the mechanical design optimization of a robot arm. Although the robot arm is non-redundant, the proposed method modifies robot arm kinematics by adding virtual joints to make the robot arm kinematically redundant. In the proposed method, a suitable objective function is selected to optimize the robot arm’s kinematic parameters by enhancing one or more performance indices. Then the robot arm’s end-effector is fixed at critical positions while the redundancy resolution algorithm moves its joints including the virtual joints because of the self-motion of a redundant robot. Hence, the optimum values of the virtual joints are determined, and the design of the robot arm is modified accordingly. An advantage of this method is the visualization of the changes in the manipulator’s structure during the optimization process. In this work, as a case study, a passive robotic arm that is used in a surgical robot system is considered and the task is defined as the determination of the optimum base location and the first link’s length. The results indicate the effectiveness of the proposed method. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Redundancy resolution techniques have been widely used for the control of kinematically redundant robots. In this work, one of the redundancy resolution techniques is employed in the mechanical design optimization of a robot arm. Although the robot arm is non-redundant, the proposed method modifies robot arm kinematics by adding virtual joints to make the robot arm kinematically redundant. In the proposed method, a suitable objective function is selected to optimize the robot arm’s kinematic parameters by enhancing one or more performance indices. Then the robot arm’s end-effector is fixed at critical positions while the redundancy resolution algorithm moves its joints including the virtual joints because of the self-motion of a redundant robot. Hence, the optimum values of the virtual joints are determined, and the design of the robot arm is modified accordingly. An advantage of this method is the visualization of the changes in the manipulator’s structure during the optimization process. In this work, as a case study, a passive robotic arm that is used in a surgical robot system is considered and the task is defined as the determination of the optimum base location and the first link’s length. The results indicate the effectiveness of the proposed method. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. |
Yenigun, O; Barisik, M Active heat transfer enhancement by interface-localized liquid dielectrophoresis using interdigitated electrodes Journal Article Carbon, 189 , pp. 339-348, 2022. @article{Yenigun2022339, title = {Active heat transfer enhancement by interface-localized liquid dielectrophoresis using interdigitated electrodes}, author = {O Yenigun and M Barisik}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85122100118&doi=10.1016%2fj.carbon.2021.12.063&partnerID=40&md5=070297f8e7ae2a455bbb8996fe221608}, doi = {10.1016/j.carbon.2021.12.063}, year = {2022}, date = {2022-01-01}, journal = {Carbon}, volume = {189}, pages = {339-348}, abstract = {We introduced an active heat transfer control between graphene and water using interdigitated electrodes (IDEs). Oppositely charged co-planer electrodes embedded on a graphene surface created a non-uniform electric field. Resulted interface localized liquid dielectrophoresis (LDEP) perpendicular to surface enhanced the water/graphene coupling and decreased interfacial thermal resistance (ITR) substantially. We correlated the theoretical calculations of average electric field strength near surface with Kapitza values measured at corresponding electrode configurations. We obtained a unified linear variation of Kapitza as a function of average electric strength independent of electrode size and charge. By increasing the electric field strength, we measured up to 96% decrease of Kapitza near electrodes. Since the IDEs generated electric field was only interface localized, it required lower electrode charges than any parallel-plate capacitor systems. We showed that ITR remains effective in heat transfer behavior for systems as big as 100nm such that interface localized electric field can at least increase the heat removal 50% by eliminating the ITR from both graphene/water interfaces of a channel system. By converting hydrophobic few-layer graphene to super-hydrophilic condition with ultra-low Kapitza, current results are important for graphene-based materials considered for the solution of the thermal management problem of current and next generation micro/nano-electronics. © 2021}, keywords = {}, pubstate = {published}, tppubtype = {article} } We introduced an active heat transfer control between graphene and water using interdigitated electrodes (IDEs). Oppositely charged co-planer electrodes embedded on a graphene surface created a non-uniform electric field. Resulted interface localized liquid dielectrophoresis (LDEP) perpendicular to surface enhanced the water/graphene coupling and decreased interfacial thermal resistance (ITR) substantially. We correlated the theoretical calculations of average electric field strength near surface with Kapitza values measured at corresponding electrode configurations. We obtained a unified linear variation of Kapitza as a function of average electric strength independent of electrode size and charge. By increasing the electric field strength, we measured up to 96% decrease of Kapitza near electrodes. Since the IDEs generated electric field was only interface localized, it required lower electrode charges than any parallel-plate capacitor systems. We showed that ITR remains effective in heat transfer behavior for systems as big as 100nm such that interface localized electric field can at least increase the heat removal 50% by eliminating the ITR from both graphene/water interfaces of a channel system. By converting hydrophobic few-layer graphene to super-hydrophilic condition with ultra-low Kapitza, current results are important for graphene-based materials considered for the solution of the thermal management problem of current and next generation micro/nano-electronics. © 2021 |
Sabet, S; Barisik, M; Buonomo, B; Manca, O Thermal and hydrodynamic behavior of forced convection gaseous slip flow in a Kelvin cell metal foam Journal Article International Communications in Heat and Mass Transfer, 131 , 2022. @article{Sabet2022, title = {Thermal and hydrodynamic behavior of forced convection gaseous slip flow in a Kelvin cell metal foam}, author = {S Sabet and M Barisik and B Buonomo and O Manca}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85121421292&doi=10.1016%2fj.icheatmasstransfer.2021.105838&partnerID=40&md5=014f7a382ce37a13408f90bd5c6be444}, doi = {10.1016/j.icheatmasstransfer.2021.105838}, year = {2022}, date = {2022-01-01}, journal = {International Communications in Heat and Mass Transfer}, volume = {131}, abstract = {Porous metallic foams are a key material in numerous thermal and hydraulic applications. Gas flows in such micro/nanoporous systems deviate from classical continuum descriptions due to nonequilibrium in gas dynamics, and the resulted heat and mass transport show variation by rarefaction. This study performed a wide range of pore-level analysis of convective gas flows in a Kelvin cell model at different porosities and working conditions. Rarefaction effects onto permeability and heat transfer coefficients were calculated through Darcy to Forchheimer flow regimes. Permeability increased up to 60% by increasing rarefaction while this enhancement decreased by increasing porosity. At the same time, rarefaction lessened inertial effects such that Forchheimer coefficients decreased substantially. At high flow velocities, the increase in rarefaction considerably decreased the effect of drag forces. Hence, hydrodynamic enhancement due to rarefaction was found to increase by increasing Reynolds number. On the other hand, positive influence of boundary slip and negative influence of temperature jump developing between gas and solid almost canceled each other for the studied low heat flux region of highly conductive metal foam structures. Hence, Nusselt numbers were found mostly related to Reynolds number independent from rarefaction. We described Nusselt value based on power law model as a function of Reynolds and porosity. Results and the proposed model are important to accurately predict the thermal and hydrodynamic performance of metal foams in the 80 PPI range. © 2021}, keywords = {}, pubstate = {published}, tppubtype = {article} } Porous metallic foams are a key material in numerous thermal and hydraulic applications. Gas flows in such micro/nanoporous systems deviate from classical continuum descriptions due to nonequilibrium in gas dynamics, and the resulted heat and mass transport show variation by rarefaction. This study performed a wide range of pore-level analysis of convective gas flows in a Kelvin cell model at different porosities and working conditions. Rarefaction effects onto permeability and heat transfer coefficients were calculated through Darcy to Forchheimer flow regimes. Permeability increased up to 60% by increasing rarefaction while this enhancement decreased by increasing porosity. At the same time, rarefaction lessened inertial effects such that Forchheimer coefficients decreased substantially. At high flow velocities, the increase in rarefaction considerably decreased the effect of drag forces. Hence, hydrodynamic enhancement due to rarefaction was found to increase by increasing Reynolds number. On the other hand, positive influence of boundary slip and negative influence of temperature jump developing between gas and solid almost canceled each other for the studied low heat flux region of highly conductive metal foam structures. Hence, Nusselt numbers were found mostly related to Reynolds number independent from rarefaction. We described Nusselt value based on power law model as a function of Reynolds and porosity. Results and the proposed model are important to accurately predict the thermal and hydrodynamic performance of metal foams in the 80 PPI range. © 2021 |
Sahin, R C; Gocmen, S; Cetkin, E Thermal management system for air-cooled battery packs with flow-disturbing structures Journal Article Journal of Power Sources, 551 , 2022. @article{Sahin2022b, title = {Thermal management system for air-cooled battery packs with flow-disturbing structures}, author = {R C Sahin and S Gocmen and E Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85140273371&doi=10.1016%2fj.jpowsour.2022.232214&partnerID=40&md5=b488f0477918b1e6b4dd91f0627d4578}, doi = {10.1016/j.jpowsour.2022.232214}, year = {2022}, date = {2022-01-01}, journal = {Journal of Power Sources}, volume = {551}, abstract = {Lithium-ion battery packs are preferred in electrical vehicles (EVs) due to their efficient and stable characteristics. Battery thermal management systems (BTMS) have vital importance in EVs to keep batteries in the desired temperature range to maximize performance and lifetime. BTMS with air cooling is simpler and lighter relative to competing methods; however, low thermal conductivity and heat capacity of air necessitate thermal performance and pressure drop adjustments. This work offers a novel design method for cylindrical cells by evaluating the effect of various baffles (cylindrical, triangular, diamond and winglet) on the cooling performance and pressure drop of an air-cooled battery module with 12 21700 cylindrical cells. Thermal characteristics are simulated by the electrochemical-thermal battery model, the P3D multiscale model (modelling parameters for a commercial 21700 cell are documented) in COMSOL Multiphysics 5.5 and their accuracy is validated by experiments. As a result, baffles reduce the maximum temperature and temperature difference by 5% (1.8 °C) and 40% (1.7 °C), respectively, consuming 3.5 times more power than the base design. Delta winglets offer the optimum solution, reducing the maximum temperature and temperature difference by 2% (0.6 °C) and 15% (0.7 °C), respectively, with a 44% (0.12 W) rise in parasitic power consumption. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Lithium-ion battery packs are preferred in electrical vehicles (EVs) due to their efficient and stable characteristics. Battery thermal management systems (BTMS) have vital importance in EVs to keep batteries in the desired temperature range to maximize performance and lifetime. BTMS with air cooling is simpler and lighter relative to competing methods; however, low thermal conductivity and heat capacity of air necessitate thermal performance and pressure drop adjustments. This work offers a novel design method for cylindrical cells by evaluating the effect of various baffles (cylindrical, triangular, diamond and winglet) on the cooling performance and pressure drop of an air-cooled battery module with 12 21700 cylindrical cells. Thermal characteristics are simulated by the electrochemical-thermal battery model, the P3D multiscale model (modelling parameters for a commercial 21700 cell are documented) in COMSOL Multiphysics 5.5 and their accuracy is validated by experiments. As a result, baffles reduce the maximum temperature and temperature difference by 5% (1.8 °C) and 40% (1.7 °C), respectively, consuming 3.5 times more power than the base design. Delta winglets offer the optimum solution, reducing the maximum temperature and temperature difference by 2% (0.6 °C) and 15% (0.7 °C), respectively, with a 44% (0.12 W) rise in parasitic power consumption. © 2022 Elsevier B.V. |
Gungor, S; Cetkin, E Enhanced temperature uniformity with minimized pressure drop in electric vehicle battery packs at elevated C-rates Journal Article Heat Transfer, 51 (8), pp. 7540-7561, 2022. @article{Gungor20227540, title = {Enhanced temperature uniformity with minimized pressure drop in electric vehicle battery packs at elevated C-rates}, author = {S Gungor and E Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85135263580&doi=10.1002%2fhtj.22654&partnerID=40&md5=3b91b531fb44340686649125afd2a02a}, doi = {10.1002/htj.22654}, year = {2022}, date = {2022-01-01}, journal = {Heat Transfer}, volume = {51}, number = {8}, pages = {7540-7561}, abstract = {The trend of transition from fossil fuel to electrification in transportation is a result of no carbon emission produced by electric vehicles (EVs) during their daily operations. Furthermore, the global carbon footprint of EVs can be minimized if the electricity is generated from renewable sources such as wind and solar. On the other hand, there are some drawbacks of these vehicles such as charging time being very long and the mileage range of vehicles not at the desired level. Battery cells are being charged at relatively high C-rates to eliminate these problems, yet high current rates accelerate the aging of batteries and capacity losses due to the generated heat. Generated heat causes overheating, and excess temperature triggers degradation and thermal runaway risks. This paper uncovers how the battery pack temperature uniformity and strict thermal control can be achieved with heat transfer enhancement by conduction (cold plates) and convection (vascular channels). We aimed to reduce the energy consumption of the EV battery pack system while increasing the thermal performance. The impact of the thermal contact resistance is also considered for many realistic scenarios. The results indicate that an integrated system with cold plates and vascular channels satisfies the temperature uniformity requirement (over 81%) with comparatively less pumping power (∼72%) of advanced electric vehicles for relatively high C-rates. Furthermore, findings show the temperature level can increase up to 4°C as thermal contact resistance increases. The proposed cooling technique, which has low cost, easy application, and lower energy consumption superiorities, can be implemented in palpable EV battery packs. © 2022 Wiley Periodicals LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The trend of transition from fossil fuel to electrification in transportation is a result of no carbon emission produced by electric vehicles (EVs) during their daily operations. Furthermore, the global carbon footprint of EVs can be minimized if the electricity is generated from renewable sources such as wind and solar. On the other hand, there are some drawbacks of these vehicles such as charging time being very long and the mileage range of vehicles not at the desired level. Battery cells are being charged at relatively high C-rates to eliminate these problems, yet high current rates accelerate the aging of batteries and capacity losses due to the generated heat. Generated heat causes overheating, and excess temperature triggers degradation and thermal runaway risks. This paper uncovers how the battery pack temperature uniformity and strict thermal control can be achieved with heat transfer enhancement by conduction (cold plates) and convection (vascular channels). We aimed to reduce the energy consumption of the EV battery pack system while increasing the thermal performance. The impact of the thermal contact resistance is also considered for many realistic scenarios. The results indicate that an integrated system with cold plates and vascular channels satisfies the temperature uniformity requirement (over 81%) with comparatively less pumping power (∼72%) of advanced electric vehicles for relatively high C-rates. Furthermore, findings show the temperature level can increase up to 4°C as thermal contact resistance increases. The proposed cooling technique, which has low cost, easy application, and lower energy consumption superiorities, can be implemented in palpable EV battery packs. © 2022 Wiley Periodicals LLC. |
Gungor, S; Cetkin, E; Lorente, S Thermal and electrical characterization of an electric vehicle battery cell, an experimental investigation Journal Article Applied Thermal Engineering, 212 , 2022. @article{Gungor2022b, title = {Thermal and electrical characterization of an electric vehicle battery cell, an experimental investigation}, author = {S Gungor and E Cetkin and S Lorente}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85129534427&doi=10.1016%2fj.applthermaleng.2022.118530&partnerID=40&md5=fe9a51259b3473a5b8a99fc67ed0043c}, doi = {10.1016/j.applthermaleng.2022.118530}, year = {2022}, date = {2022-01-01}, journal = {Applied Thermal Engineering}, volume = {212}, abstract = {This paper documents the experimental characterization of a Li-ion battery cell during charging/discharging cyclic operations. The study of the battery cell is conducted in the absence of cooling aid system, and provides thermal and electrical insights. After describing the experimental set-up, the changes in temperature are presented and highlight the nonuniform distribution of the temperature on the battery cell surface. The findings indicate that the maximum temperature difference on the investigated battery cell surface may reach up to 11 C at 3C and 17 ⁰C at 5C, at the end of the discharge in the natural convection case. These changes in space come with temporal variations that are also documented. Voltage curves are provided during charging and discharging operations. The impact of the discharge rate, ambient temperature are then investigated together with the capacity fade after 500 cycles, and results showed that ventilation and low ambient temperatures allow to alleviate the battery capacity fade by 3%. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper documents the experimental characterization of a Li-ion battery cell during charging/discharging cyclic operations. The study of the battery cell is conducted in the absence of cooling aid system, and provides thermal and electrical insights. After describing the experimental set-up, the changes in temperature are presented and highlight the nonuniform distribution of the temperature on the battery cell surface. The findings indicate that the maximum temperature difference on the investigated battery cell surface may reach up to 11 C at 3C and 17 ⁰C at 5C, at the end of the discharge in the natural convection case. These changes in space come with temporal variations that are also documented. Voltage curves are provided during charging and discharging operations. The impact of the discharge rate, ambient temperature are then investigated together with the capacity fade after 500 cycles, and results showed that ventilation and low ambient temperatures allow to alleviate the battery capacity fade by 3%. © 2022 Elsevier Ltd |
Demirkıran, İ G; Rocha, L A O; Cetkin, E Emergence of asymmetric straight and branched fins in horizontally oriented latent heat thermal energy storage units Journal Article International Journal of Heat and Mass Transfer, 189 , 2022. @article{Demirkıran2022, title = {Emergence of asymmetric straight and branched fins in horizontally oriented latent heat thermal energy storage units}, author = {İ G Demirkıran and L A O Rocha and E Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125777922&doi=10.1016%2fj.ijheatmasstransfer.2022.122726&partnerID=40&md5=dfad7a7519437326f78acb3461cbaa3d}, doi = {10.1016/j.ijheatmasstransfer.2022.122726}, year = {2022}, date = {2022-01-01}, journal = {International Journal of Heat and Mass Transfer}, volume = {189}, abstract = {Mobilized thermal energy storage units have a vital role in reducing energy consumption in buildings by enabling industrial waste heat to be used in buildings. High conductive fins can enhance the heat transfer performance of mobilized thermal energy storage tanks which suffer significantly from the low thermal conductivity of phase change materials. On the other hand, investment costs of the mobilized thermal energy storage tanks need to be decreased to compete with fossil fuel-driven systems in buildings. The present study numerically investigates the effect of innovative fin structures on the melting performance for fixed fin material volume to disable cost increase. Two-dimensional models with phase change were simulated for shell-and-tube heat exchangers. The shell geometry was designed sufficiently large to observe the melting growth of phase change material independent from shell walls within the given charging time. Straight and Branched type fin structures with the fin numbers of Nfin=2, 4, and 6 were simulated to uncover the effect of shape and length scale of fins on natural convection-driven melting. It was found that Straight fin type is more suited than Branched fins as they do not show significant melting enhancement with increased complexity and cost. The fin structures in all cases performed better when located at the top of the heat transfer fluid tube, even though the literature considers that top-located fins inhibit natural convection circulations. Varying the number of fins from (2-fin) to (4-fin) causes 15.8% increase in melting ratio, but further increase in the fin number (6-fin) reduces melting ratio below the (4-fin) case. Within (4-fin) structures located at the top, using distinct fin lengths yields melting ratio to increase 28.1%. Overall, the results show that heat transfer could be improved by varying the fin structure without increasing total fin volume and cost. The melting region growth shape with optimized fin structure forms the basis for the multitube arrangement of mobilized thermal energy storage units to enhance heat transfer performance with low cost. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mobilized thermal energy storage units have a vital role in reducing energy consumption in buildings by enabling industrial waste heat to be used in buildings. High conductive fins can enhance the heat transfer performance of mobilized thermal energy storage tanks which suffer significantly from the low thermal conductivity of phase change materials. On the other hand, investment costs of the mobilized thermal energy storage tanks need to be decreased to compete with fossil fuel-driven systems in buildings. The present study numerically investigates the effect of innovative fin structures on the melting performance for fixed fin material volume to disable cost increase. Two-dimensional models with phase change were simulated for shell-and-tube heat exchangers. The shell geometry was designed sufficiently large to observe the melting growth of phase change material independent from shell walls within the given charging time. Straight and Branched type fin structures with the fin numbers of Nfin=2, 4, and 6 were simulated to uncover the effect of shape and length scale of fins on natural convection-driven melting. It was found that Straight fin type is more suited than Branched fins as they do not show significant melting enhancement with increased complexity and cost. The fin structures in all cases performed better when located at the top of the heat transfer fluid tube, even though the literature considers that top-located fins inhibit natural convection circulations. Varying the number of fins from (2-fin) to (4-fin) causes 15.8% increase in melting ratio, but further increase in the fin number (6-fin) reduces melting ratio below the (4-fin) case. Within (4-fin) structures located at the top, using distinct fin lengths yields melting ratio to increase 28.1%. Overall, the results show that heat transfer could be improved by varying the fin structure without increasing total fin volume and cost. The melting region growth shape with optimized fin structure forms the basis for the multitube arrangement of mobilized thermal energy storage units to enhance heat transfer performance with low cost. © 2022 Elsevier Ltd |
Demirkıran, İ G; Cetkin, E Computation time reduction of PCM melting process by changing modeling parameters Journal Article Numerical Heat Transfer; Part A: Applications, 83 (1), pp. 50-67, 2022. @article{Demirkıran202250, title = {Computation time reduction of PCM melting process by changing modeling parameters}, author = {İ G Demirkıran and E Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85142904241&doi=10.1080%2f10407782.2022.2149229&partnerID=40&md5=9060437b1c078c4230068c898ce0213f}, doi = {10.1080/10407782.2022.2149229}, year = {2022}, date = {2022-01-01}, journal = {Numerical Heat Transfer; Part A: Applications}, volume = {83}, number = {1}, pages = {50-67}, abstract = {This study can be considered as a helpful reference for whom endeavor to boost the computation efficiency of the PCM melting process. Researchers sacrifice accuracy to decrease computation time since computational fluid dynamics (CFD) solutions of PCM melting processes require comparatively very long time, i.e., from hours to days or weeks, depending on the system geometry. The present study compares the approaches recommended in the literature in terms of their influence on computation time reduction and accuracy. A horizontally finned tube LHTES unit is modeled in 2-D space using ANSYS Fluent, the most common commercial CFD software for the considered problem in the literature. The outcomes obtained from the attempts to boost the computation efficiency are as follows: adaptive time step size approach causes 72% enhancement in computation time (from 90 hours to 25 hours), frozen flux algorithm and constant thermophysical properties have almost no influence on computation time. Even though low convergence criteria and neglecting natural convection reduces computation time drastically, the errors in accuracy are not in acceptable level. © 2022 Taylor & Francis Group, LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study can be considered as a helpful reference for whom endeavor to boost the computation efficiency of the PCM melting process. Researchers sacrifice accuracy to decrease computation time since computational fluid dynamics (CFD) solutions of PCM melting processes require comparatively very long time, i.e., from hours to days or weeks, depending on the system geometry. The present study compares the approaches recommended in the literature in terms of their influence on computation time reduction and accuracy. A horizontally finned tube LHTES unit is modeled in 2-D space using ANSYS Fluent, the most common commercial CFD software for the considered problem in the literature. The outcomes obtained from the attempts to boost the computation efficiency are as follows: adaptive time step size approach causes 72% enhancement in computation time (from 90 hours to 25 hours), frozen flux algorithm and constant thermophysical properties have almost no influence on computation time. Even though low convergence criteria and neglecting natural convection reduces computation time drastically, the errors in accuracy are not in acceptable level. © 2022 Taylor & Francis Group, LLC. |
Gocmen, S; Cetkin, E Emergence of elevated battery positioning in air cooled battery packs for temperature uniformity in ultra-fast dis/charging applications Journal Article Journal of Energy Storage, 45 , 2022. @article{Gocmen2022, title = {Emergence of elevated battery positioning in air cooled battery packs for temperature uniformity in ultra-fast dis/charging applications}, author = {S Gocmen and E Cetkin}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85118748009&doi=10.1016%2fj.est.2021.103516&partnerID=40&md5=736e4f4ff2d5aeb573d8473e4039ed23}, doi = {10.1016/j.est.2021.103516}, year = {2022}, date = {2022-01-01}, journal = {Journal of Energy Storage}, volume = {45}, abstract = {Pure electric vehicles (EVs) are gradually becoming major interest of research in worldwide. Battery cells in EV battery packs must be kept in between the desired operational temperature range (∼30°C) and temperature should be homogeneous in packs to eliminate safety risks and prolong battery life. In this study, performance of a novel BTMS design was studied at various discharge conditions with fast and ultra-fast C-rate values. Cooling with natural convection exceeds desired operational temperature in the pack as well as forced air convection in Z-type manifold. Elevated battery positions yield flow resistance along the air channels in between battery cells to be uniform which yields flow rate sweeping the surface of each cell to be the same. Therefore, the maximum temperature in between cells decreases to less than 0.3K from the order of 12K. The temperature uniformity is essential for ageing and electrical resistance of cells to be homogeneous in a pack. In addition, heat transfer enhancement with various fin designs is documented as well as its effect on the temperature distribution. The accuracy of numerical studies is validated by experimental work. The results show that the peak temperature can be kept under the desired operational temperature with minimum deviation in the temperature difference for distinct operation conditions required for advanced electric vehicles (cars, airplanes, helicopters) with extreme charging and discharging capability. © 2021 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Pure electric vehicles (EVs) are gradually becoming major interest of research in worldwide. Battery cells in EV battery packs must be kept in between the desired operational temperature range (∼30°C) and temperature should be homogeneous in packs to eliminate safety risks and prolong battery life. In this study, performance of a novel BTMS design was studied at various discharge conditions with fast and ultra-fast C-rate values. Cooling with natural convection exceeds desired operational temperature in the pack as well as forced air convection in Z-type manifold. Elevated battery positions yield flow resistance along the air channels in between battery cells to be uniform which yields flow rate sweeping the surface of each cell to be the same. Therefore, the maximum temperature in between cells decreases to less than 0.3K from the order of 12K. The temperature uniformity is essential for ageing and electrical resistance of cells to be homogeneous in a pack. In addition, heat transfer enhancement with various fin designs is documented as well as its effect on the temperature distribution. The accuracy of numerical studies is validated by experimental work. The results show that the peak temperature can be kept under the desired operational temperature with minimum deviation in the temperature difference for distinct operation conditions required for advanced electric vehicles (cars, airplanes, helicopters) with extreme charging and discharging capability. © 2021 Elsevier Ltd |
Gungor, S; Cetkin, E; Lorente, S 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{Gungor2022c, title = {Canopy-to-canopy liquid cooling for the thermal management of lithium-ion batteries, a constructal approach}, author = {S Gungor and E Cetkin and S Lorente}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85114670203&doi=10.1016%2fj.ijheatmasstransfer.2021.121918&partnerID=40&md5=705da93dfe3b91f9ec006e9534aa4333}, 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. © 2021}, 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. © 2021 |
Ciklacandir, S; Mihcin, S; Isler, Y IRBM, 43 (6), pp. 604-613, 2022. @article{Ciklacandir2022604, title = {Detailed Investigation of Three-Dimensional Modeling and Printing Technologies from Medical Images to Analyze Femoral Head Fractures Using Finite Element Analysis}, author = {S Ciklacandir and S Mihcin and Y Isler}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85129883533&doi=10.1016%2fj.irbm.2022.04.005&partnerID=40&md5=31017add921b2693916e42e10bdb9b45}, doi = {10.1016/j.irbm.2022.04.005}, year = {2022}, date = {2022-01-01}, journal = {IRBM}, volume = {43}, number = {6}, pages = {604-613}, abstract = {Objectives: One of the fields, where additive manufacturing has numerous applications, is biomedical engineering. 3D printing is preferred over traditional manufacturing methodologies, mostly while developing subject-specific implants and medical devices. This study aims to provide a process flow detailing all the stages starting from the acquisition of radiological images from different imaging modalities; such as computed tomography (CT) and magnetic resonance imaging (MRI) to the printing of the bone morphology and finite element analysis; including the validation process. Materials & Methods: First, the CT scan of a lower abdomen area of a patient was converted into a 3D image using interactive medical imaging control system software. The segmentation process was applied to isolate the femoral head from the soft tissue and the pelvic bone. After the roughness errors and the gaps in the segments were removed using the 3Matic software, the file was converted to stereolithography (STL) file format to transfer to the 3D printer. The printing process was carried out via commercial powder-based Selective Laser Sintering (SLS) printer. The subject-specific femoral head model was formed in 3D. The Finite Element Analysis (FEA) of the femoral head was performed using a commercial FE software package. Results: The results show that experimental analysis and the CT scan-based FEA were compatible both for the stress distributions and the strain values as predicted by the models (R2=0.99). The deviation was calculated as approximately 12% between the experimental results and the Finite Element (FE) results. In addition, it was observed that the SLS technique produced useful results for modeling biomedical tissues with about 24x faster prototyping time. Conclusion: The prescribed process flow could be utilized in clinical settings for the pre-planning of the surgeries (≈428 minutes for femoral head) and also as an educational tool in the biomedical engineering field. © 2022 AGBM}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objectives: One of the fields, where additive manufacturing has numerous applications, is biomedical engineering. 3D printing is preferred over traditional manufacturing methodologies, mostly while developing subject-specific implants and medical devices. This study aims to provide a process flow detailing all the stages starting from the acquisition of radiological images from different imaging modalities; such as computed tomography (CT) and magnetic resonance imaging (MRI) to the printing of the bone morphology and finite element analysis; including the validation process. Materials & Methods: First, the CT scan of a lower abdomen area of a patient was converted into a 3D image using interactive medical imaging control system software. The segmentation process was applied to isolate the femoral head from the soft tissue and the pelvic bone. After the roughness errors and the gaps in the segments were removed using the 3Matic software, the file was converted to stereolithography (STL) file format to transfer to the 3D printer. The printing process was carried out via commercial powder-based Selective Laser Sintering (SLS) printer. The subject-specific femoral head model was formed in 3D. The Finite Element Analysis (FEA) of the femoral head was performed using a commercial FE software package. Results: The results show that experimental analysis and the CT scan-based FEA were compatible both for the stress distributions and the strain values as predicted by the models (R2=0.99). The deviation was calculated as approximately 12% between the experimental results and the Finite Element (FE) results. In addition, it was observed that the SLS technique produced useful results for modeling biomedical tissues with about 24x faster prototyping time. Conclusion: The prescribed process flow could be utilized in clinical settings for the pre-planning of the surgeries (≈428 minutes for femoral head) and also as an educational tool in the biomedical engineering field. © 2022 AGBM |
Ulu, A; Yildiz, G; Rodriguez, A D; Özkol, Ü Spray Analysis of Biodiesels Derived from Various Biomass Resources in a Constant Volume Spray Chamber Journal Article ACS Omega, 7 (23), pp. 19365-19379, 2022. @article{Ulu202219365, title = {Spray Analysis of Biodiesels Derived from Various Biomass Resources in a Constant Volume Spray Chamber}, author = {A Ulu and G Yildiz and A D Rodriguez and Ü Özkol}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85132107803&doi=10.1021%2facsomega.2c00952&partnerID=40&md5=995ab045ec0310695a47b69c61b69c80}, doi = {10.1021/acsomega.2c00952}, year = {2022}, date = {2022-01-01}, journal = {ACS Omega}, volume = {7}, number = {23}, pages = {19365-19379}, abstract = {This research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5-18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2-35.1% larger SMD values and approximately 7% lower air entrainment. © 2022 American Chemical Society. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5-18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2-35.1% larger SMD values and approximately 7% lower air entrainment. © 2022 American Chemical Society. All rights reserved. |
Ulu, A; Yildiz, G; Özkol, Ü; Rodriguez, A D Experimental investigation of spray characteristics of ethyl esters in a constant volume chamber Journal Article Biomass Conversion and Biorefinery, 2022. @article{Ulu2022b, title = {Experimental investigation of spray characteristics of ethyl esters in a constant volume chamber}, author = {A Ulu and G Yildiz and Ü Özkol and A D 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 = {2022}, date = {2022-01-01}, journal = {Biomass Conversion and Biorefinery}, 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. |
Esenoğlu, G; Barisik, M; Tanoğlu, M; Yeke, M; Türkdoğan, C; İplikçi, H; Martin, S; Nuhoğlu, K; Aktaş, E; Dehneliler, S; İriş, M E Improving adhesive behavior of fiber reinforced composites by incorporating electrospun Polyamide-6,6 nanofibers in joining region Journal Article Journal of Composite Materials, 56 (29), pp. 4449-4459, 2022. @article{Esenoğlu20224449, title = {Improving adhesive behavior of fiber reinforced composites by incorporating electrospun Polyamide-6,6 nanofibers in joining region}, author = {G Esenoğlu and M Barisik and M Tanoğlu and M Yeke and C Türkdoğan and H İplikçi and S Martin and K Nuhoğlu and E Aktaş and S Dehneliler and M E İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85139985112&doi=10.1177%2f00219983221133478&partnerID=40&md5=699a47f9c6bc7948245cdc6f370c483e}, doi = {10.1177/00219983221133478}, year = {2022}, date = {2022-01-01}, journal = {Journal of Composite Materials}, volume = {56}, number = {29}, pages = {4449-4459}, abstract = {Adhesive joining of fiber reinforced polymer (CFRP) composite components is demanded in various industrial applications. However, the joining locations frequently suffer from adhesive bond failure between adhesive and adherent. The aim of the present study is improving bonding behavior of adhesive joints by electrospun nanofiber coatings on the prepreg surfaces that have been used for composite manufacturing. Secondary bonding of woven and unidirectional CFRP parts was selected since this configuration is preferred commonly in aerospace practices. The optimum nanofiber coating with a low average fiber diameter and areal weight density is succeed by studying various solution concentrations and spinning durations of the polyamide-6.6 (PA 66) electrospinning. We obtained homogeneous and beadles nanofiber productions. As a result, an average diameter of 36.50 ± 12 nm electrospun nanofibers were obtained and coated onto the prepreg surfaces. Prepreg systems with/without PA 66 nanofibers were hot pressed to fabricate the CFRP composite laminates. The single-lap shear test coupons were prepared from the fabricated laminates to examine the effects of PA 66 nanofibers on the mechanical properties of the joint region of the composites. The single-lap shear test results showed that the bonding strength is improved by about 40% with minimal adhesive use due to the presence of the electrospun nanofibers within the joint region. The optical and SEM images of fractured surfaces showed that nanofiber-coated joints exhibited a coherent failure while the bare surfaces underwent adhesive failure. The PA66 nanofibers created better coupling between the adhesive and the composite surface by increasing the surface area and roughness. As a result, electrospun nanofibers turned adhesive failure into cohesive and enhanced the adhesion performance composite joints substantially. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Adhesive joining of fiber reinforced polymer (CFRP) composite components is demanded in various industrial applications. However, the joining locations frequently suffer from adhesive bond failure between adhesive and adherent. The aim of the present study is improving bonding behavior of adhesive joints by electrospun nanofiber coatings on the prepreg surfaces that have been used for composite manufacturing. Secondary bonding of woven and unidirectional CFRP parts was selected since this configuration is preferred commonly in aerospace practices. The optimum nanofiber coating with a low average fiber diameter and areal weight density is succeed by studying various solution concentrations and spinning durations of the polyamide-6.6 (PA 66) electrospinning. We obtained homogeneous and beadles nanofiber productions. As a result, an average diameter of 36.50 ± 12 nm electrospun nanofibers were obtained and coated onto the prepreg surfaces. Prepreg systems with/without PA 66 nanofibers were hot pressed to fabricate the CFRP composite laminates. The single-lap shear test coupons were prepared from the fabricated laminates to examine the effects of PA 66 nanofibers on the mechanical properties of the joint region of the composites. The single-lap shear test results showed that the bonding strength is improved by about 40% with minimal adhesive use due to the presence of the electrospun nanofibers within the joint region. The optical and SEM images of fractured surfaces showed that nanofiber-coated joints exhibited a coherent failure while the bare surfaces underwent adhesive failure. The PA66 nanofibers created better coupling between the adhesive and the composite surface by increasing the surface area and roughness. As a result, electrospun nanofibers turned adhesive failure into cohesive and enhanced the adhesion performance composite joints substantially. © The Author(s) 2022. |
Güneş, M D; Karabaş, İmamoğlu N; Deveci, H A; Tanoğlu, G; Tanoğlu, M Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 236 (19), pp. 10290-10303, 2022. @article{Güneş202210290, title = {Fatigue life prediction and optimization of GFRP composites based on Failure Tensor Polynomial in Fatigue model with exponential fitting approach}, author = {M D Güneş and N İmamoğlu Karabaş and H A Deveci and G Tanoğlu and M Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130983288&doi=10.1177%2f09544062221101462&partnerID=40&md5=144a189eaf81ed03065a753253307cad}, doi = {10.1177/09544062221101462}, year = {2022}, date = {2022-01-01}, journal = {Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science}, volume = {236}, number = {19}, pages = {10290-10303}, abstract = {In this study, a new fatigue life prediction and optimization strategy utilizing the Failure Tensor Polynomial in Fatigue (FTPF) model with exponential fitting and numerical bisection method for fiber reinforced polymer composites has been proposed. Within the experimental stage, glass/epoxy composite laminates with (Formula presented.), (Formula presented.), and (Formula presented.) lay-up configurations were fabricated, quasi-static and fatigue mechanical behavior of GFRP composites was characterized to be used in the FTPF model. The prediction capability of the FTPF model was tested based on the experimental data obtained for multidirectional laminates of various composite materials. Fatigue life prediction results of the glass/epoxy laminates were found to be better as compared to those for the linear fitting predictions. The results also indicated that the approach with exponential fitting provides better fatigue life predictions as compared to those obtained by linear fitting, especially for glass/epoxy laminates. Moreover, an optimization study using the proposed methodology for fatigue life advancement of the glass/epoxy laminates was performed by a powerful hybrid algorithm, PSA/GPSA. So, two optimization scenarios including various loading configurations were considered. The optimization results exhibited that the optimized stacking sequences having maximized fatigue life can be obtained in various loading cases. It was also revealed that the tension-compression loading and the loadings involving shear loads are critical for fatigue, and further improvement in fatigue life may be achieved by designing only symmetric lay-ups instead of symmetric-balanced and diversification of fiber angles to be used in the optimization. © IMechE 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a new fatigue life prediction and optimization strategy utilizing the Failure Tensor Polynomial in Fatigue (FTPF) model with exponential fitting and numerical bisection method for fiber reinforced polymer composites has been proposed. Within the experimental stage, glass/epoxy composite laminates with (Formula presented.), (Formula presented.), and (Formula presented.) lay-up configurations were fabricated, quasi-static and fatigue mechanical behavior of GFRP composites was characterized to be used in the FTPF model. The prediction capability of the FTPF model was tested based on the experimental data obtained for multidirectional laminates of various composite materials. Fatigue life prediction results of the glass/epoxy laminates were found to be better as compared to those for the linear fitting predictions. The results also indicated that the approach with exponential fitting provides better fatigue life predictions as compared to those obtained by linear fitting, especially for glass/epoxy laminates. Moreover, an optimization study using the proposed methodology for fatigue life advancement of the glass/epoxy laminates was performed by a powerful hybrid algorithm, PSA/GPSA. So, two optimization scenarios including various loading configurations were considered. The optimization results exhibited that the optimized stacking sequences having maximized fatigue life can be obtained in various loading cases. It was also revealed that the tension-compression loading and the loadings involving shear loads are critical for fatigue, and further improvement in fatigue life may be achieved by designing only symmetric lay-ups instead of symmetric-balanced and diversification of fiber angles to be used in the optimization. © IMechE 2022. |
Üstün, Sinan H; Toksoy, Kaan A; Tanoğlu, M Investigation of hybridization effect on ballistic performance of multi-layered fiber reinforced composite structures Journal Article Journal of Composite Materials, 56 (15), pp. 2411-2431, 2022. @article{SinanÜstün20222411, title = {Investigation of hybridization effect on ballistic performance of multi-layered fiber reinforced composite structures}, author = {H Sinan Üstün and A Kaan Toksoy and M Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130035790&doi=10.1177%2f00219983221090018&partnerID=40&md5=c04588512f22392bf8cac3ef9d118408}, doi = {10.1177/00219983221090018}, year = {2022}, date = {2022-01-01}, journal = {Journal of Composite Materials}, volume = {56}, number = {15}, pages = {2411-2431}, abstract = {The aim of this study is enhancing the ballistic performance of multi-layered fiber reinforced composite structures by hybridization approach against fragment simulating projectile (FSP). For manufacturing of homogeneous and hybrid composite structures, 170 g/m2 twill weave aramid and 280 g/m2 plain weave E-Glass fibers were used with epoxy resin systems and two different thickness values for each composite panel were fabricated and tested to obtain a relationship between areal density and V50 parameters. Tensile, 3-point bending, and short beam strength tests of composite panels were performed, and ballistic performance of composite structures were measured by V50 test method with 1.1 g FSP threat. Ballistic performance of hybrid composite structures was compared with high-performance composite ballistic panel test results reported in literature. As a result, it was found that E-Glass fabric layers together with aramid fabrics increased the energy absorbing capability of hybrid composite panels and ballistic performance was enhanced to be similar or higher than ballistic fiber reinforced composites. Hence, hybridization was found to be an effective way to enhance ballistic performance of fiber reinforced composite structures. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this study is enhancing the ballistic performance of multi-layered fiber reinforced composite structures by hybridization approach against fragment simulating projectile (FSP). For manufacturing of homogeneous and hybrid composite structures, 170 g/m2 twill weave aramid and 280 g/m2 plain weave E-Glass fibers were used with epoxy resin systems and two different thickness values for each composite panel were fabricated and tested to obtain a relationship between areal density and V50 parameters. Tensile, 3-point bending, and short beam strength tests of composite panels were performed, and ballistic performance of composite structures were measured by V50 test method with 1.1 g FSP threat. Ballistic performance of hybrid composite structures was compared with high-performance composite ballistic panel test results reported in literature. As a result, it was found that E-Glass fabric layers together with aramid fabrics increased the energy absorbing capability of hybrid composite panels and ballistic performance was enhanced to be similar or higher than ballistic fiber reinforced composites. Hence, hybridization was found to be an effective way to enhance ballistic performance of fiber reinforced composite structures. © The Author(s) 2022. |
Uz, Y C; Tanoğlu, M Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry Journal Article High Performance Polymers, 2022. @article{Uz2022, title = {Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry}, author = {Y C Uz and M 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 = {2022}, date = {2022-01-01}, journal = {High Performance Polymers}, 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. |
Solak, Ay Z; Kartav, O; Tanoglu, M Enhancement of filament wound glass fiber/epoxy-based cylindrical composites by toughening with single-walled carbon nanotubes Journal Article Polymers and Polymer Composites, 30 , 2022. @article{AySolak2022, title = {Enhancement of filament wound glass fiber/epoxy-based cylindrical composites by toughening with single-walled carbon nanotubes}, author = {Z Ay Solak and O Kartav and M Tanoglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85131795670&doi=10.1177%2f09673911221086718&partnerID=40&md5=ee2274734defe29b42d80148622b6359}, doi = {10.1177/09673911221086718}, year = {2022}, date = {2022-01-01}, journal = {Polymers and Polymer Composites}, volume = {30}, abstract = {In this study, the effect of incorporating nano-sized fillers (noncovalently functionalized with ethoxylated alcohol chemical-vapor-deposition-grown SWCNTs) within an epoxy resin on the performance of filament wound glass fiber (GF)-based cylindrical composites (GFCCs) was investigated. For this purpose, SWCNTs were dispersed with the concentration of 0.05 and 0.1 weight percent (wt.%) within an epoxy resin using mechanical stirring and calendaring (3-roll-milling) techniques. The rheological behavior of the SWCNT incorporated epoxy mixture was characterized to determine the suitability of blends for the filament winding process. It was revealed that the viscosity value of the resin was not significantly affected by the addition of SWCNTs in given concentrations. Moreover, contact angle measurements were also performed on the SWCNT/epoxy blends dropped on the GF for the evaluation of the wettability behavior of the GF in the presence of the SWCNTs in relevant concentrations. Eventually, it was observed that the wettability behavior of GF was not reasonably affected by the presence of the SWCNTs. The double cantilever beam (DCB), flexural, and short beam shear (SBS) tests were performed on the reference and SWCNT-modified GFCC specimens to evaluate the effects of the SWCNT presence on the interlaminar fracture toughness and out-of-plane properties of GFCCs. The fractured surfaces after the DCB and SBS tests were analyzed under the scanning electron microscopy to reveal the toughening mechanisms and the filler morphologies. Consequently, although SWCNT incorporation was on the outermost layer of GFCCs, it was found that the interlaminar shear strength (ILSS) values and Mode I interlaminar fracture toughness values of the curved composite samples were improved up to 22 and 216%, respectively, due to the presence of the SWCNTs. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the effect of incorporating nano-sized fillers (noncovalently functionalized with ethoxylated alcohol chemical-vapor-deposition-grown SWCNTs) within an epoxy resin on the performance of filament wound glass fiber (GF)-based cylindrical composites (GFCCs) was investigated. For this purpose, SWCNTs were dispersed with the concentration of 0.05 and 0.1 weight percent (wt.%) within an epoxy resin using mechanical stirring and calendaring (3-roll-milling) techniques. The rheological behavior of the SWCNT incorporated epoxy mixture was characterized to determine the suitability of blends for the filament winding process. It was revealed that the viscosity value of the resin was not significantly affected by the addition of SWCNTs in given concentrations. Moreover, contact angle measurements were also performed on the SWCNT/epoxy blends dropped on the GF for the evaluation of the wettability behavior of the GF in the presence of the SWCNTs in relevant concentrations. Eventually, it was observed that the wettability behavior of GF was not reasonably affected by the presence of the SWCNTs. The double cantilever beam (DCB), flexural, and short beam shear (SBS) tests were performed on the reference and SWCNT-modified GFCC specimens to evaluate the effects of the SWCNT presence on the interlaminar fracture toughness and out-of-plane properties of GFCCs. The fractured surfaces after the DCB and SBS tests were analyzed under the scanning electron microscopy to reveal the toughening mechanisms and the filler morphologies. Consequently, although SWCNT incorporation was on the outermost layer of GFCCs, it was found that the interlaminar shear strength (ILSS) values and Mode I interlaminar fracture toughness values of the curved composite samples were improved up to 22 and 216%, respectively, due to the presence of the SWCNTs. © The Author(s) 2022. |
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 |
Cetkin, E; Miguel, A F Asymmetric Y-shaped Micromixers with Spherical Mixing Chamber for Enhanced Mixing Efficiency and Reduced Flow Impedance Journal Article JOURNAL OF APPLIED FLUID MECHANICS, 14 (5), pp. 1389-1397, 2021. @article{WOS:000658420100009, title = {Asymmetric Y-shaped Micromixers with Spherical Mixing Chamber for Enhanced Mixing Efficiency and Reduced Flow Impedance}, author = {E Cetkin and A F Miguel}, doi = {10.47176/jafm.14.05.32317}, year = {2021}, date = {2021-09-01}, journal = {JOURNAL OF APPLIED FLUID MECHANICS}, volume = {14}, number = {5}, pages = {1389-1397}, abstract = {Microfluidic devices have many attractive qualities such as low cost, small size, and in-field use. Micromixers are very important components of these devices because affect their efficiency. In a passive mixer, the structural characteristics of the mixer are crucial and must be analyzed. This paper presents a numerical study of the mixing in passive Y-shaped micromixers with a spherical mixing chamber for a volume constrained system. The effect of asymmetric bifurcated ducts, the angle in between the inflow ducts, eccentricity and, obstacles inserted in the mixing sphere, on the mixing efficiency and flow impedance is evaluated. Vortical structures characteristics and the possible occurrence of engulfment are also identified. The results show that flow impedance (pressure drop for unit volumetric flow rate) can be decreased greatly for the same mixing efficiency as the volume of the spherical mixing chamber is 20% of the total volume. Insertion of the obstacles into the sphere mixing chamber decreases the mixing efficiency while they increase the flow impedance. The results also show that spherical mixing chamber enhances mixing efficiency while decreasing flow impedance if the volume reserved for it is greater than a limit value which depends on the diameter and length scale ratios in between the mother and daughter ducts as well as the total volume. Overall, the paper documents the variation of mixing efficiency and flow impedance based on the geometrical parameters of three-dimensional asymmetric passive micromixer with sphere mixing chamber.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Microfluidic devices have many attractive qualities such as low cost, small size, and in-field use. Micromixers are very important components of these devices because affect their efficiency. In a passive mixer, the structural characteristics of the mixer are crucial and must be analyzed. This paper presents a numerical study of the mixing in passive Y-shaped micromixers with a spherical mixing chamber for a volume constrained system. The effect of asymmetric bifurcated ducts, the angle in between the inflow ducts, eccentricity and, obstacles inserted in the mixing sphere, on the mixing efficiency and flow impedance is evaluated. Vortical structures characteristics and the possible occurrence of engulfment are also identified. The results show that flow impedance (pressure drop for unit volumetric flow rate) can be decreased greatly for the same mixing efficiency as the volume of the spherical mixing chamber is 20% of the total volume. Insertion of the obstacles into the sphere mixing chamber decreases the mixing efficiency while they increase the flow impedance. The results also show that spherical mixing chamber enhances mixing efficiency while decreasing flow impedance if the volume reserved for it is greater than a limit value which depends on the diameter and length scale ratios in between the mother and daughter ducts as well as the total volume. Overall, the paper documents the variation of mixing efficiency and flow impedance based on the geometrical parameters of three-dimensional asymmetric passive micromixer with sphere mixing chamber. |
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. |
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. |
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. |
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. |
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. |
Şahin, O N; Dede, M İ C Investigation of longitudinal friction characteristics of an omnidirectional wheel via LuGre model Journal Article Robotica, 39 (9), pp. 1654-1673, 2021. @article{Şahin20211654, title = {Investigation of longitudinal friction characteristics of an omnidirectional wheel via LuGre model}, author = {O N Şahin and M İ C Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85100396480&doi=10.1017%2fS0263574720001423&partnerID=40&md5=87b564f58915fb537015ba9bc579f540}, doi = {10.1017/S0263574720001423}, year = {2021}, date = {2021-01-01}, journal = {Robotica}, volume = {39}, number = {9}, pages = {1654-1673}, abstract = {In recent years, omnidirectional wheels have found more applications in the design of automated guided vehicles (AGV). In this work, LuGre friction model is used for an omnidirectional wheel. A test setup that includes a single omnidirectional wheel is designed and constructed to identify the model parameters. With the help of the constructed test setup, the longitudinal friction characteristic of the omnidirectional wheel is obtained, and the model is verified via validation tests. In addition, for the first time, the effect of lateral frictional force on longitudinal motion is examined for an omnidirectional wheel through experiments. © 2021 Cambridge University Press. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In recent years, omnidirectional wheels have found more applications in the design of automated guided vehicles (AGV). In this work, LuGre friction model is used for an omnidirectional wheel. A test setup that includes a single omnidirectional wheel is designed and constructed to identify the model parameters. With the help of the constructed test setup, the longitudinal friction characteristic of the omnidirectional wheel is obtained, and the model is verified via validation tests. In addition, for the first time, the effect of lateral frictional force on longitudinal motion is examined for an omnidirectional wheel through experiments. © 2021 Cambridge University Press. All rights reserved. |
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 |
Görgülü, I; Dede, M I C; Carbone, G Experimental structural stiffness analysis of a surgical haptic master device manipulator Journal Article Journal of Medical Devices, Transactions of the ASME, 15 (1), 2021. @article{Görgülü2021, title = {Experimental structural stiffness analysis of a surgical haptic master device manipulator}, author = {I Görgülü and M I C Dede and G Carbone}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104310305&doi=10.1115%2f1.4049515&partnerID=40&md5=048e166dbd6c463f1f09a4381bcbab93}, doi = {10.1115/1.4049515}, year = {2021}, date = {2021-01-01}, journal = {Journal of Medical Devices, Transactions of the ASME}, volume = {15}, number = {1}, abstract = {This paper deals with haptic devices for master-slave telesurgical applications. Namely, a stiffness model fitting methodology and its fine-tuning are proposed based on experimental results. In particular, the proposed procedure is based on virtual joint structural stiffness modeling to be applied in time-efficient compliance compensation strategies. A specific case study is discussed by referring to the HISS haptic device that has been developed and built at Izmir Institute of Technology. Two different experimental setups are designed for stiffness evaluation tests. Experimental results are discussed to demonstrate their implementation in the proposed methodology for the fine-tuning of stiffness model. © 2021 by ASME}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper deals with haptic devices for master-slave telesurgical applications. Namely, a stiffness model fitting methodology and its fine-tuning are proposed based on experimental results. In particular, the proposed procedure is based on virtual joint structural stiffness modeling to be applied in time-efficient compliance compensation strategies. A specific case study is discussed by referring to the HISS haptic device that has been developed and built at Izmir Institute of Technology. Two different experimental setups are designed for stiffness evaluation tests. Experimental results are discussed to demonstrate their implementation in the proposed methodology for the fine-tuning of stiffness model. © 2021 by ASME |
Uzunoǧlu, E; Tatlicioǧlu, E; Dede, M İ C A Multi-Priority Controller for Industrial Macro-Micro Manipulation Journal Article Robotica, 39 (2), pp. 217-232, 2021. @article{Uzunoǧlu2021217, title = {A Multi-Priority Controller for Industrial Macro-Micro Manipulation}, author = {E Uzunoǧlu and E Tatlicioǧlu and M İ C Dede}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085752198&doi=10.1017%2fS0263574720000338&partnerID=40&md5=95fe3fbdfd64d096223263ac48141bbb}, doi = {10.1017/S0263574720000338}, year = {2021}, date = {2021-01-01}, journal = {Robotica}, volume = {39}, number = {2}, pages = {217-232}, abstract = {In this study, a control algorithm is proposed and evaluated for a special type of kinematically redundant manipulator. This manipulator is comprised of two mechanisms, macro and micro mechanisms, with distinct acceleration and work space characteristics. A control algorithm is devised to minimize the task completion duration and the overall actuator effort with respect to the conventional manipulator. A general framework multi-priority controller for macro-micro manipulators is introduced by utilizing virtual dynamics, which is introduced in null-space projection to achieve secondary tasks. The proposed controller is evaluated on a simulation model based on a previously constructed macro-micro manipulator for planar laser cutting. Task completion duration and the total actuator effort are investigated and the results are compared. Copyright © The Author(s), 2020. Published by Cambridge University Press.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a control algorithm is proposed and evaluated for a special type of kinematically redundant manipulator. This manipulator is comprised of two mechanisms, macro and micro mechanisms, with distinct acceleration and work space characteristics. A control algorithm is devised to minimize the task completion duration and the overall actuator effort with respect to the conventional manipulator. A general framework multi-priority controller for macro-micro manipulators is introduced by utilizing virtual dynamics, which is introduced in null-space projection to achieve secondary tasks. The proposed controller is evaluated on a simulation model based on a previously constructed macro-micro manipulator for planar laser cutting. Task completion duration and the total actuator effort are investigated and the results are compared. Copyright © The Author(s), 2020. Published by Cambridge University Press. |
Aydin, L; Artem, H S; Deveci, H A Single- and Multiobjective Optimizations of Dimensionally Stable Composites Using Genetic Algorithms Journal Article Mechanics of Composite Materials, 57 (3), pp. 321-336, 2021. @article{Aydin2021321, title = {Single- and Multiobjective Optimizations of Dimensionally Stable Composites Using Genetic Algorithms}, author = {L Aydin and H S Artem and H A Deveci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85110920003&doi=10.1007%2fs11029-021-09957-y&partnerID=40&md5=c69289acc580f74cfaae88cb543a9cef}, doi = {10.1007/s11029-021-09957-y}, year = {2021}, date = {2021-01-01}, journal = {Mechanics of Composite Materials}, volume = {57}, number = {3}, pages = {321-336}, abstract = {The present study aims to design stacking sequences of dimensionally stable symmetric balanced laminated carbon/epoxy composites, with different numbers of layers, with a low coefficient of thermal expansion and high elastic moduli. To avoid excessive interlaminar stresses in the composites, the contiguity constraint for plies is also taken into consideration. In the design process, both single- and multiobjective optimization approaches, including genetic algorithms, are utilized. Results showed that stacking sequences ensuring lower thermal expansion coefficients and higher elastic moduli than those of traditional laminate designs can be obtained. © 2021, Springer Science+Business Media, LLC, part of Springer Nature.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study aims to design stacking sequences of dimensionally stable symmetric balanced laminated carbon/epoxy composites, with different numbers of layers, with a low coefficient of thermal expansion and high elastic moduli. To avoid excessive interlaminar stresses in the composites, the contiguity constraint for plies is also taken into consideration. In the design process, both single- and multiobjective optimization approaches, including genetic algorithms, are utilized. Results showed that stacking sequences ensuring lower thermal expansion coefficients and higher elastic moduli than those of traditional laminate designs can be obtained. © 2021, Springer Science+Business Media, LLC, part of Springer Nature. |
Alan, B O; Barisik, M Size and roughness dependent temperature effects on surface charge of silica nanoparticles Journal Article Colloids and Surfaces A: Physicochemical and Engineering Aspects, 629 , 2021. @article{Alan2021, title = {Size and roughness dependent temperature effects on surface charge of silica nanoparticles}, author = {B O Alan and M Barisik}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85113802606&doi=10.1016%2fj.colsurfa.2021.127407&partnerID=40&md5=88470bff4bf146cfb5c2054495edf0c1}, doi = {10.1016/j.colsurfa.2021.127407}, year = {2021}, date = {2021-01-01}, journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects}, volume = {629}, abstract = {Silica nanoparticles (SNP) with different sizes and surface areas are used in numerous micro/nanofluidic applications, while their surface charge properties play a major role in their function. In many of these applications, SNPs also undergo temperature variation. We present that an increase in temperature yields a substantial increase in SNP surface charge depending on nanoparticle size and surface roughness, which cannot be estimated by existing theory. As a continuation of our earlier work characterizing the deviation of SNP surface charging from theoretical predictions due to curvature and EDL overlap effects, this study presents the differentiation from the theory in temperature dependence under various conditions. As we calculate surface chemistry as a function of local ionic conditions (Charge Regulation), temperature variation changed the equilibrium constants of protonation/deprotonation reactions of the SNP surface, in addition to changes occurring in relative permittivity and ionic mobilities. Results show that variation of SNP surface charge by temperature decreases by decreasing particle size and/or increasing roughness size, compare to theoretical flat plate calculations considering similar temperature-dependent properties and charge regulation on the surface. We characterized these deviations by obtaining an “electrokinetic similarity” between different systems of various size and roughness at various ionic conditions based on the non-dimensional groups of λ/DP and λ/DR. Based on these, we devised a phenomenological model as an extension to the flat plate theory to successfully predict the surface charge of SNPs as a function of the particle size, roughness size, and temperature. The current findings are important for the characterization of SNPs through temperature variations and can also be used to adjust the surface charge of SNPs by tuning the temperature. © 2021 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Silica nanoparticles (SNP) with different sizes and surface areas are used in numerous micro/nanofluidic applications, while their surface charge properties play a major role in their function. In many of these applications, SNPs also undergo temperature variation. We present that an increase in temperature yields a substantial increase in SNP surface charge depending on nanoparticle size and surface roughness, which cannot be estimated by existing theory. As a continuation of our earlier work characterizing the deviation of SNP surface charging from theoretical predictions due to curvature and EDL overlap effects, this study presents the differentiation from the theory in temperature dependence under various conditions. As we calculate surface chemistry as a function of local ionic conditions (Charge Regulation), temperature variation changed the equilibrium constants of protonation/deprotonation reactions of the SNP surface, in addition to changes occurring in relative permittivity and ionic mobilities. Results show that variation of SNP surface charge by temperature decreases by decreasing particle size and/or increasing roughness size, compare to theoretical flat plate calculations considering similar temperature-dependent properties and charge regulation on the surface. We characterized these deviations by obtaining an “electrokinetic similarity” between different systems of various size and roughness at various ionic conditions based on the non-dimensional groups of λ/DP and λ/DR. Based on these, we devised a phenomenological model as an extension to the flat plate theory to successfully predict the surface charge of SNPs as a function of the particle size, roughness size, and temperature. The current findings are important for the characterization of SNPs through temperature variations and can also be used to adjust the surface charge of SNPs by tuning the temperature. © 2021 Elsevier B.V. |
Yenigun, O; Barisik, M Local Heat Transfer Control using Liquid Dielectrophoresis at Graphene/Water Interfaces Journal Article International Journal of Heat and Mass Transfer, 166 , 2021. @article{Yenigun2021, title = {Local Heat Transfer Control using Liquid Dielectrophoresis at Graphene/Water Interfaces}, author = {O Yenigun and M Barisik}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097790790&doi=10.1016%2fj.ijheatmasstransfer.2020.120801&partnerID=40&md5=e8754da2dd49beb00b7eb1432717ea55}, doi = {10.1016/j.ijheatmasstransfer.2020.120801}, year = {2021}, date = {2021-01-01}, journal = {International Journal of Heat and Mass Transfer}, volume = {166}, abstract = {Graphene-based materials are considered for the solution of the thermal management problem of current and next generation micro/nano-electronics with high heat generation densities. However, the hydrophobic nature of few-layer graphene makes passing heat to a fluid very challenging. We introduced an active and local manipulation of heat transfer between graphene and water using an applied, non-uniform electric field. When water undergoes electric field induced orientation polarization and liquid dielectrophoresis, a substantial increase in heat transfer develops due to a decrease in interfacial thermal resistance and increase in thermal conductivity. By using two locally embedded pin and plate electrodes of different sizes, we demonstrated a two-dimensional heat transfer control between two parallel few-layer graphene slabs. We obtained local heat transfer increase up to nine times at pin electrode region with an ultra-low Kapitza resistance through the studied non-uniform electric field strength range creating highly-ordered compressed water in the experimentally measured density limits. With this technique, heat can be (i) distributed from a smaller location to a larger section and/or (ii) collected to a smaller section from a larger region. Current results are important for hot spot cooling and/or heat focusing applications. © 2020}, keywords = {}, pubstate = {published}, tppubtype = {article} } Graphene-based materials are considered for the solution of the thermal management problem of current and next generation micro/nano-electronics with high heat generation densities. However, the hydrophobic nature of few-layer graphene makes passing heat to a fluid very challenging. We introduced an active and local manipulation of heat transfer between graphene and water using an applied, non-uniform electric field. When water undergoes electric field induced orientation polarization and liquid dielectrophoresis, a substantial increase in heat transfer develops due to a decrease in interfacial thermal resistance and increase in thermal conductivity. By using two locally embedded pin and plate electrodes of different sizes, we demonstrated a two-dimensional heat transfer control between two parallel few-layer graphene slabs. We obtained local heat transfer increase up to nine times at pin electrode region with an ultra-low Kapitza resistance through the studied non-uniform electric field strength range creating highly-ordered compressed water in the experimentally measured density limits. With this technique, heat can be (i) distributed from a smaller location to a larger section and/or (ii) collected to a smaller section from a larger region. Current results are important for hot spot cooling and/or heat focusing applications. © 2020 |
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. |
Kandemir, S; Gavras, S; Dieringa, H Journal of Magnesium and Alloys, 9 (5), pp. 1753-1767, 2021. @article{Kandemir20211753, title = {High temperature tensile, compression and creep behavior of recycled short carbon fibre reinforced AZ91 magnesium alloy fabricated by a high shearing dispersion technique}, author = {S Kandemir and S Gavras and H Dieringa}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85106274015&doi=10.1016%2fj.jma.2021.03.029&partnerID=40&md5=33482583e6489310dc991aed7c7b0793}, doi = {10.1016/j.jma.2021.03.029}, year = {2021}, date = {2021-01-01}, journal = {Journal of Magnesium and Alloys}, volume = {9}, number = {5}, pages = {1753-1767}, abstract = {The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021 |
Martin, S; Kandemir, S; Antonov, M Investigation of the high temperature dry sliding wear behavior of graphene nanoplatelets reinforced aluminum matrix composites Journal Article Journal of Composite Materials, 55 (13), pp. 1769-1782, 2021. @article{Martin20211769, title = {Investigation of the high temperature dry sliding wear behavior of graphene nanoplatelets reinforced aluminum matrix composites}, author = {S Martin and S Kandemir and M Antonov}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097279024&doi=10.1177%2f0021998320979037&partnerID=40&md5=554c5ed3fcc37de88e360d033402ed4b}, doi = {10.1177/0021998320979037}, year = {2021}, date = {2021-01-01}, journal = {Journal of Composite Materials}, volume = {55}, number = {13}, pages = {1769-1782}, abstract = {In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020. |
Kartav, O; Kangal, S; Yücetürk, K; Tanoğlu, M; Aktaş, E; Artem, H S Development and analysis of composite overwrapped pressure vessels for hydrogen storage Journal Article Journal of Composite Materials, 55 (28), pp. 4141-4155, 2021. @article{Kartav20214141, title = {Development and analysis of composite overwrapped pressure vessels for hydrogen storage}, author = {O Kartav and S Kangal and K Yücetürk and M Tanoğlu and E Aktaş and H S Artem}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85110939454&doi=10.1177%2f00219983211033568&partnerID=40&md5=c31db8e0f0de63135bf2da9bf634900d}, doi = {10.1177/00219983211033568}, year = {2021}, date = {2021-01-01}, journal = {Journal of Composite Materials}, volume = {55}, number = {28}, pages = {4141-4155}, abstract = {In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance. © The Author(s) 2021.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance. © The Author(s) 2021. |
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 |
Sarialtin, H; Geyer, R; Zafer, C Environmental assessment of transparent conductive oxide-free efficient flexible organo-lead halide perovskite solar cell Journal Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects, 43 (20), pp. 2544-2553, 2021. @article{Sarialtin20212544, title = {Environmental assessment of transparent conductive oxide-free efficient flexible organo-lead halide perovskite solar cell}, author = {H Sarialtin and R Geyer and C Zafer}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095721962&doi=10.1080%2f15567036.2020.1842560&partnerID=40&md5=fce22be696576207a0d582736c5feda1}, doi = {10.1080/15567036.2020.1842560}, year = {2021}, date = {2021-01-01}, journal = {Energy Sources, Part A: Recovery, Utilization and Environmental Effects}, volume = {43}, number = {20}, pages = {2544-2553}, abstract = {Perovskite solar cells (PSCs), one of the third-generation photovoltaic (PV) technologies, have recently become a very popular topic in photovoltaic research. This technology, which is a candidate for commercialization in the future, needs to be evaluated from an environmental point of view. The amount of electricity consumption is the most important factor that directly determines the environmental impact values of photovoltaic cell manufacturing. Transparent conductive oxide (TCO) coated glass is one of the major contributors to electricity consumption in PSC architecture. It is therefore useful to investigate the environmental profile of TCO coated glass-free PSC architecture with conventional PVs. One of the solutions to this issue is manufacturing PSC on a flexible substrate. Flexible PVs are considered to be one of the most promising candidates for mass production with its advantages of low-temperature manufacturing, higher efficiency with a lower weight, portability, and compatibility with a roll to roll fabrication. In this work, we show that the environmental impacts of a representative PSCs with a flexible substrate. While the energy payback time (EPBT) of the flexible PSC is already competitive with commercial PVs, the device must reach a 25-year cell lifetime for its global warming potential (GWP) to reach a reasonable range. © 2020 Taylor & Francis Group, LLC.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Perovskite solar cells (PSCs), one of the third-generation photovoltaic (PV) technologies, have recently become a very popular topic in photovoltaic research. This technology, which is a candidate for commercialization in the future, needs to be evaluated from an environmental point of view. The amount of electricity consumption is the most important factor that directly determines the environmental impact values of photovoltaic cell manufacturing. Transparent conductive oxide (TCO) coated glass is one of the major contributors to electricity consumption in PSC architecture. It is therefore useful to investigate the environmental profile of TCO coated glass-free PSC architecture with conventional PVs. One of the solutions to this issue is manufacturing PSC on a flexible substrate. Flexible PVs are considered to be one of the most promising candidates for mass production with its advantages of low-temperature manufacturing, higher efficiency with a lower weight, portability, and compatibility with a roll to roll fabrication. In this work, we show that the environmental impacts of a representative PSCs with a flexible substrate. While the energy payback time (EPBT) of the flexible PSC is already competitive with commercial PVs, the device must reach a 25-year cell lifetime for its global warming potential (GWP) to reach a reasonable range. © 2020 Taylor & Francis Group, LLC. |
Uzer-Yilmaz, B In vitro contact guidance of glioblastoma cells on metallic biomaterials Journal Article Journal of Materials Science: Materials in Medicine, 32 (4), 2021. @article{Uzer-Yilmaz2021, title = {In vitro contact guidance of glioblastoma cells on metallic biomaterials}, author = {B Uzer-Yilmaz}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103594796&doi=10.1007%2fs10856-021-06503-z&partnerID=40&md5=3df5859593f38e768004318b90d166df}, doi = {10.1007/s10856-021-06503-z}, year = {2021}, date = {2021-01-01}, journal = {Journal of Materials Science: Materials in Medicine}, volume = {32}, number = {4}, abstract = {Cancer cells’ ability to sense their microenvironment and interpret these signals for the regulation of directional adhesion plays crucial role in cancer invasion. Furthermore, given the established influence of mechanical properties of the substrate on cell behavior, the present study aims to elucidate the relationship between the contact guidance of glioblastoma cell (GBM) and evolution of microstructural and mechanical properties of the implants. SEM analyses of the specimens subjected to 5 and 25% of plastic strains revealed directional groove-like structures in micro and submicro-sizes, respectively. Microscale cytoplasmic protrusions of GBMs showed elongation favored along the grooves created via deformation markings on 5% deformed sample. Whereas filopodia, submicro-sized protrusions facilitating cancer invasion, elongated in the direction perpendicular to the deformation markings on the 25% deformed sample, which might lead to easy and rapid retraction. Furthermore, number of cell attachment was 1.7-fold greater on 25% deformed sample, where these cells showed the greatest cellular aspect ratio. The directional attachment and contact guidance of GBMs was reported for the first time on metallic implants and these findings propose the idea that GBM response could be regulated by controlling the spacing of the deformation markings, namely the degree of plastic deformation. These findings can be applied in the design of cell-instructive implants for therapeutic purposes to suppress cancer dissemination. [Figure not available: see fulltext.] © 2021, The Author(s).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Cancer cells’ ability to sense their microenvironment and interpret these signals for the regulation of directional adhesion plays crucial role in cancer invasion. Furthermore, given the established influence of mechanical properties of the substrate on cell behavior, the present study aims to elucidate the relationship between the contact guidance of glioblastoma cell (GBM) and evolution of microstructural and mechanical properties of the implants. SEM analyses of the specimens subjected to 5 and 25% of plastic strains revealed directional groove-like structures in micro and submicro-sizes, respectively. Microscale cytoplasmic protrusions of GBMs showed elongation favored along the grooves created via deformation markings on 5% deformed sample. Whereas filopodia, submicro-sized protrusions facilitating cancer invasion, elongated in the direction perpendicular to the deformation markings on the 25% deformed sample, which might lead to easy and rapid retraction. Furthermore, number of cell attachment was 1.7-fold greater on 25% deformed sample, where these cells showed the greatest cellular aspect ratio. The directional attachment and contact guidance of GBMs was reported for the first time on metallic implants and these findings propose the idea that GBM response could be regulated by controlling the spacing of the deformation markings, namely the degree of plastic deformation. These findings can be applied in the design of cell-instructive implants for therapeutic purposes to suppress cancer dissemination. [Figure not available: see fulltext.] © 2021, The Author(s). |
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. |
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. |
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. |
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. |
Ozcelik, Gokberk H; Satiroglu, Ezgi; Barisik, Murat Size dependent influence of contact line pinning on wetting of nano-textured/patterned silica surfaces Journal Article NANOSCALE, 12 (41), pp. 21376-21391, 2020, ISSN: 2040-3364. @article{ISI:000584907600029, title = {Size dependent influence of contact line pinning on wetting of nano-textured/patterned silica surfaces}, author = {Gokberk H Ozcelik and Ezgi Satiroglu and Murat Barisik}, doi = {10.1039/d0nr05392a}, issn = {2040-3364}, year = {2020}, date = {2020-11-01}, journal = {NANOSCALE}, volume = {12}, number = {41}, pages = {21376-21391}, abstract = {Wetting behavior on a heterogeneous surface undergoes contact angle hysteresis as the droplet stabilized at a metastable state with a contact angle significantly different from its equilibrium value due to contact line pinning. However, there is a lack of consensus on how to calculate the influence of pinning forces. In general, the pinning effect can be characterized as (i) microscopic behavior when a droplet is pinned and the contact angle increases/decreases as the droplet volume increases/decreases and (ii) macroscopic behavior as the pinning effects decrease and ultimately, disappear with the increase of the droplet size. The current work studied both behaviors using molecular dynamics (MD) simulation with more than 300 different size water droplets on silica surfaces with three different patterns across two different wetting conditions. Results showed that the contact angle increases linearly with increasing droplet volume through the microscopic behavior, while the droplet is pinned on top of a certain number of patterns. When we normalized the droplet size with the corresponding pattern size, we observed a ``wetting similarity'' that linear microscopic contact angle variations over different size heterogeneities continuously line up. This shows that the pinning force remains constant and the resulting pinning effects are scalable by the size ratio between the droplet and pattern, independent of the size-scale. The slope of these microscopic linear variations decreases with an increase in the droplet size as observed through the macroscopic behavior. We further found a universal behavior in the variation of the corresponding pinning forces, independent of the wetting condition. In macroscopic behavior, pinning effects become negligible and the contact angle reaches the equilibrium value of the corresponding surface when the diameter of the free-standing droplet is approximately equal to 24 times the size of the surface structure. We found that the pinning effect is scalable with the droplet volume, not the size of the droplet base.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Wetting behavior on a heterogeneous surface undergoes contact angle hysteresis as the droplet stabilized at a metastable state with a contact angle significantly different from its equilibrium value due to contact line pinning. However, there is a lack of consensus on how to calculate the influence of pinning forces. In general, the pinning effect can be characterized as (i) microscopic behavior when a droplet is pinned and the contact angle increases/decreases as the droplet volume increases/decreases and (ii) macroscopic behavior as the pinning effects decrease and ultimately, disappear with the increase of the droplet size. The current work studied both behaviors using molecular dynamics (MD) simulation with more than 300 different size water droplets on silica surfaces with three different patterns across two different wetting conditions. Results showed that the contact angle increases linearly with increasing droplet volume through the microscopic behavior, while the droplet is pinned on top of a certain number of patterns. When we normalized the droplet size with the corresponding pattern size, we observed a ``wetting similarity'' that linear microscopic contact angle variations over different size heterogeneities continuously line up. This shows that the pinning force remains constant and the resulting pinning effects are scalable by the size ratio between the droplet and pattern, independent of the size-scale. The slope of these microscopic linear variations decreases with an increase in the droplet size as observed through the macroscopic behavior. We further found a universal behavior in the variation of the corresponding pinning forces, independent of the wetting condition. In macroscopic behavior, pinning effects become negligible and the contact angle reaches the equilibrium value of the corresponding surface when the diameter of the free-standing droplet is approximately equal to 24 times the size of the surface structure. We found that the pinning effect is scalable with the droplet volume, not the size of the droplet base. |
Ay, Z; Tanoglu, M The Effect of Single-Walled Carbon Nanotube (SWCNT) Concentration on the Mechanical and Rheological Behavior of Epoxy Matrix Journal Article MECHANICS OF COMPOSITE MATERIALS, 56 (4), pp. 523-532, 2020, ISSN: 0191-5665. @article{ISI:000567735300002, title = {The Effect of Single-Walled Carbon Nanotube (SWCNT) Concentration on the Mechanical and Rheological Behavior of Epoxy Matrix}, author = {Z Ay and M Tanoglu}, doi = {10.1007/s11029-020-09900-7, Early Access Date = SEP 2020}, issn = {0191-5665}, year = {2020}, date = {2020-09-01}, journal = {MECHANICS OF COMPOSITE MATERIALS}, volume = {56}, number = {4}, pages = {523-532}, abstract = {The improvement of Mode I fracture toughness of epoxy by the addition of single-walled carbon nanotubes (SWCNTs) is considered. To prepare nanocomposites, chemical-vapor-deposition-grown SWCNTs noncovalently functionalized with an ethoxylated alcohol was used as the additive and a diglycidyl ether of bisphenol-A-based epoxy as the matrix material. The SWCNTs were dispersed in the epoxy matrix via a mechanical stirrer and a 3-roll mill. The effect of their concentration (0.0125, 0.025, 0.05, 0.1, 0.3, and 0.5 wt.%) on the mechanical properties of the nanocomposites was investigated, and the optimum concentration was determined. Mode I fracture toughness (single-edge-notch 3-point bending) and tensile tests were carried out on neat epoxy and SWCNT-reinforced epoxy nanocomposites. The fractured surfaces of fracture toughness and tensile test specimens were examined by the SEM to reveal the effect of SWCNTs on their failure modes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The improvement of Mode I fracture toughness of epoxy by the addition of single-walled carbon nanotubes (SWCNTs) is considered. To prepare nanocomposites, chemical-vapor-deposition-grown SWCNTs noncovalently functionalized with an ethoxylated alcohol was used as the additive and a diglycidyl ether of bisphenol-A-based epoxy as the matrix material. The SWCNTs were dispersed in the epoxy matrix via a mechanical stirrer and a 3-roll mill. The effect of their concentration (0.0125, 0.025, 0.05, 0.1, 0.3, and 0.5 wt.%) on the mechanical properties of the nanocomposites was investigated, and the optimum concentration was determined. Mode I fracture toughness (single-edge-notch 3-point bending) and tensile tests were carried out on neat epoxy and SWCNT-reinforced epoxy nanocomposites. The fractured surfaces of fracture toughness and tensile test specimens were examined by the SEM to reveal the effect of SWCNTs on their failure modes. |
Yakin, Fetiye Esin; Barisik, Murat; Sen, Tumcan Pore Size and Porosity Dependent Zeta Potentials of Mesoporous Silica Nanoparticles Journal Article JOURNAL OF PHYSICAL CHEMISTRY C, 124 (36), pp. 19579-19587, 2020, ISSN: 1932-7447. @article{ISI:000571497000020, title = {Pore Size and Porosity Dependent Zeta Potentials of Mesoporous Silica Nanoparticles}, author = {Fetiye Esin Yakin and Murat Barisik and Tumcan Sen}, doi = {10.1021/acs.jpcc.0c04602}, issn = {1932-7447}, year = {2020}, date = {2020-09-01}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {124}, number = {36}, pages = {19579-19587}, abstract = {Mesoporous silica nanoparticles (MSNPs) are synthesized in the various forms of porous structures according to an application's needs, while their zeta potentials play a major role in their function. We show that variation in pore size and/or porosity yields a substantial decrease in MSNP zeta potential up to 25% lower than the theoretical zeta potential predictions for a flat surface at the corresponding ionic conditions in moderate pH range. By considering surface chemistry as a function of local ionic conditions (charge regulation), we calculated local zeta potentials around the MSNP which showed variation between pore openings and solid surfaces. Through a systematic study, we evaluated an average three-dimensional zeta potential for MSNPs with various conditions, based on the ratio of the area covered by pore openings to the rest of the MSNP surface area as a function of three-dimensional porosity and pore size. Results show that the high overlap of ionic layers inside the pores creates electric potentials close to zeta potential of the remaining surface, but large pore size and/or high ionic salt concentration yields divergence. We characterized the variation of MSNP zeta potential in terms of porosity (epsilon(3D)), pore size (D-pore), and ionic condition quantified by Debye length (lambda) and obtained unified behavior as a function of the nondimensional group of epsilon(3D)(D-pore/lambda). For epsilon(3D)(D-pore/lambda) < 0.01, MSNP zeta potential remains similar to flat plate predictions, but it decreases by increasing epsilon(3D)(D-pore/lambda) value. The influence of pore entrances on surface zeta potential increases nonlinearly by the increase of porosity and/or decrease of EDL overlap, similar to a change of area to volume ratio. The current findings are important for the understanding and further control of mesoporous particle transport in various promising and groundbreaking applications such as targeted drug delivery.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mesoporous silica nanoparticles (MSNPs) are synthesized in the various forms of porous structures according to an application's needs, while their zeta potentials play a major role in their function. We show that variation in pore size and/or porosity yields a substantial decrease in MSNP zeta potential up to 25% lower than the theoretical zeta potential predictions for a flat surface at the corresponding ionic conditions in moderate pH range. By considering surface chemistry as a function of local ionic conditions (charge regulation), we calculated local zeta potentials around the MSNP which showed variation between pore openings and solid surfaces. Through a systematic study, we evaluated an average three-dimensional zeta potential for MSNPs with various conditions, based on the ratio of the area covered by pore openings to the rest of the MSNP surface area as a function of three-dimensional porosity and pore size. Results show that the high overlap of ionic layers inside the pores creates electric potentials close to zeta potential of the remaining surface, but large pore size and/or high ionic salt concentration yields divergence. We characterized the variation of MSNP zeta potential in terms of porosity (epsilon(3D)), pore size (D-pore), and ionic condition quantified by Debye length (lambda) and obtained unified behavior as a function of the nondimensional group of epsilon(3D)(D-pore/lambda). For epsilon(3D)(D-pore/lambda) < 0.01, MSNP zeta potential remains similar to flat plate predictions, but it decreases by increasing epsilon(3D)(D-pore/lambda) value. The influence of pore entrances on surface zeta potential increases nonlinearly by the increase of porosity and/or decrease of EDL overlap, similar to a change of area to volume ratio. The current findings are important for the understanding and further control of mesoporous particle transport in various promising and groundbreaking applications such as targeted drug delivery. |
Sen, Tumcan; Barisik, Murat Slip Effects on Ionic Current of Viscoelectric Electroviscous Flows through Different Length Nanofluidic Channels Journal Article LANGMUIR, 36 (31), pp. 9191-9203, 2020, ISSN: 0743-7463. @article{ISI:000562137700018, title = {Slip Effects on Ionic Current of Viscoelectric Electroviscous Flows through Different Length Nanofluidic Channels}, author = {Tumcan Sen and Murat Barisik}, doi = {10.1021/acs.langmuir.0c01457}, issn = {0743-7463}, year = {2020}, date = {2020-08-01}, journal = {LANGMUIR}, volume = {36}, number = {31}, pages = {9191-9203}, abstract = {The pressure driven slip flow of an electrolyte solution is studied through different nanofluidic channel lengths at varying salt concentrations. The viscous-thickening due to the electrostatic interactions within the electric double layer and the reverse ionic transport due to the streaming potential are developed. The influence of the Navier slip boundary condition is described under both electroviscous and viscoelectric effects with a surface charge regulation (CR) model while the observed behavior is compared and validated with molecular dynamic (MD) calculations from multiple studies. Results show that electroviscous and viscoelectric effects decrease transport. Earlier studies at the no slip boundary presented an increase of ionic current by increasing salt concentration and decreasing channel length. In contrast, our study found that the ionic current occurred almost independent of both salt concentration and channel length, except for very short channels and very low salt concentrations, when electroviscous and viscoelectric effects were considered. In the case of the constant slip length condition, ionic conduction was enhanced, but velocity slip developing on surfaces showed significant variation based on the salt concentration and channel length. This is due to the natural CR behavior enhancing the surface charge and consequential near surface electrohydrodynamics as a result of increase in salt concentration and/or decrease of channel length. Considering that the electroviscous effect alone creates up to 70% lower velocity slips than Poiseuille flow predictions, while further including the viscoelectric effect, results in an almost no-slip condition at high salt concentrations and/or short channels. As a result, the ionic current of a viscoelectric electroviscous slip flow is found to be equal to 1/3 of an electroviscous slip flow and to decrease with a decrease in the channel length.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The pressure driven slip flow of an electrolyte solution is studied through different nanofluidic channel lengths at varying salt concentrations. The viscous-thickening due to the electrostatic interactions within the electric double layer and the reverse ionic transport due to the streaming potential are developed. The influence of the Navier slip boundary condition is described under both electroviscous and viscoelectric effects with a surface charge regulation (CR) model while the observed behavior is compared and validated with molecular dynamic (MD) calculations from multiple studies. Results show that electroviscous and viscoelectric effects decrease transport. Earlier studies at the no slip boundary presented an increase of ionic current by increasing salt concentration and decreasing channel length. In contrast, our study found that the ionic current occurred almost independent of both salt concentration and channel length, except for very short channels and very low salt concentrations, when electroviscous and viscoelectric effects were considered. In the case of the constant slip length condition, ionic conduction was enhanced, but velocity slip developing on surfaces showed significant variation based on the salt concentration and channel length. This is due to the natural CR behavior enhancing the surface charge and consequential near surface electrohydrodynamics as a result of increase in salt concentration and/or decrease of channel length. Considering that the electroviscous effect alone creates up to 70% lower velocity slips than Poiseuille flow predictions, while further including the viscoelectric effect, results in an almost no-slip condition at high salt concentrations and/or short channels. As a result, the ionic current of a viscoelectric electroviscous slip flow is found to be equal to 1/3 of an electroviscous slip flow and to decrease with a decrease in the channel length. |
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. |
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. |
Alan, Oyku B; Barisik, Murat; Ozcelik, Gokberk H Roughness Effects on the Surface Charge Properties of Silica Nanoparticles Journal Article JOURNAL OF PHYSICAL CHEMISTRY C, 124 (13), pp. 7274-7286, 2020, ISSN: 1932-7447. @article{ISI:000526328500032, title = {Roughness Effects on the Surface Charge Properties of Silica Nanoparticles}, author = {Oyku B Alan and Murat Barisik and Gokberk H Ozcelik}, doi = {10.1021/acs.jpcc.0c00120}, issn = {1932-7447}, year = {2020}, date = {2020-04-01}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {124}, number = {13}, pages = {7274-7286}, abstract = {The surface charge property of silica nanoparticles plays a key role in their function. Previous studies assumed surface charge as a homogeneously distributed constant material property, independent of the nanoparticle size and surface condition. Instead, this study considered surface chemistry as a function of local ionic conditions (Charge Regulation) to calculate the local surface charges around a rough nanoparticle, as an extension to our earlier study (J. Phys. Chem. C 2014, 118 (4), 1836-1842). For the current surface heterogeneity in the form of concave and convex circles, the surface charge showed a distinct local variation: decrease due to the electrical double layer (EDL) overlap in the valleys and increase due to curvature effects on the hills of the surface structure. The average of local surface charges decreased with the decrease of the roughness size (D-R), depending on the particle size (D-P) and pH. We characterized the variation of the average surface charge by a nondimensional group we formed as a measure for the EDL overlap and curvature effects [(D-R/lambda) x (D-R/D-P)]. Based on this, we devised a phenomenological model as an extension to the existing flat surface theory, which can successfully predict the average surface charge around a rough/patterned nanoparticle as a function of the particle size, roughness size, and pH.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The surface charge property of silica nanoparticles plays a key role in their function. Previous studies assumed surface charge as a homogeneously distributed constant material property, independent of the nanoparticle size and surface condition. Instead, this study considered surface chemistry as a function of local ionic conditions (Charge Regulation) to calculate the local surface charges around a rough nanoparticle, as an extension to our earlier study (J. Phys. Chem. C 2014, 118 (4), 1836-1842). For the current surface heterogeneity in the form of concave and convex circles, the surface charge showed a distinct local variation: decrease due to the electrical double layer (EDL) overlap in the valleys and increase due to curvature effects on the hills of the surface structure. The average of local surface charges decreased with the decrease of the roughness size (D-R), depending on the particle size (D-P) and pH. We characterized the variation of the average surface charge by a nondimensional group we formed as a measure for the EDL overlap and curvature effects [(D-R/lambda) x (D-R/D-P)]. Based on this, we devised a phenomenological model as an extension to the existing flat surface theory, which can successfully predict the average surface charge around a rough/patterned nanoparticle as a function of the particle size, roughness size, and pH. |
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. |
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. |
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. |
Toprak, K; Ouedraogo, K E Effect of storage tanks on solar-powered absorption chiller cooling system performance Journal Article International Journal of Energy Research, 44 (6), pp. 4366-4375, 2020. @article{Toprak20204366, title = {Effect of storage tanks on solar-powered absorption chiller cooling system performance}, author = {K Toprak and K E Ouedraogo}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079718680&doi=10.1002%2fer.5210&partnerID=40&md5=aa6c4b8eb29c64ec8849ffdd43934cc6}, doi = {10.1002/er.5210}, year = {2020}, date = {2020-01-01}, journal = {International Journal of Energy Research}, volume = {44}, number = {6}, pages = {4366-4375}, abstract = {Thermal storage, low power tariff at night, and low nocturnal temperature can be used in synergy to reduce the cooling costs of the solar-powered absorption chiller cooling systems. This study aims to reduce the required cooling capacity of an absorption chiller (ACH) powered by a solar parabolic trough collector (PTC) and a backup fuel boiler by integrating thermal storage tanks. The thermal performance of the system is simulated for a building that is cooled for 14 h/day. The system uses 1000 m2 PTC with 1020 kW ACH. Chilled water storage (CHWS) and cooling water storage (CWS) effects on the system performance for different operation hours per day of the ACH under Izmir (Turkey) and Phoenix (USA) weather conditions are analyzed. When the ACH operates 14 h/day as the load for both systems and both locations, the variations of the solar collector efficiency and the cooling load to heat input ratio remain less than 4% after the modifications. From the addition of CHWS to the reference system, a parametric study consisting of changing the ACH operation hours per day shows that the required cooling capacity of the ACH can be reduced to 34%. The capacity factor of the ACH is improved from its reference value of 41% up to 96%. © 2020 John Wiley & Sons Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thermal storage, low power tariff at night, and low nocturnal temperature can be used in synergy to reduce the cooling costs of the solar-powered absorption chiller cooling systems. This study aims to reduce the required cooling capacity of an absorption chiller (ACH) powered by a solar parabolic trough collector (PTC) and a backup fuel boiler by integrating thermal storage tanks. The thermal performance of the system is simulated for a building that is cooled for 14 h/day. The system uses 1000 m2 PTC with 1020 kW ACH. Chilled water storage (CHWS) and cooling water storage (CWS) effects on the system performance for different operation hours per day of the ACH under Izmir (Turkey) and Phoenix (USA) weather conditions are analyzed. When the ACH operates 14 h/day as the load for both systems and both locations, the variations of the solar collector efficiency and the cooling load to heat input ratio remain less than 4% after the modifications. From the addition of CHWS to the reference system, a parametric study consisting of changing the ACH operation hours per day shows that the required cooling capacity of the ACH can be reduced to 34%. The capacity factor of the ACH is improved from its reference value of 41% up to 96%. © 2020 John Wiley & Sons Ltd |
Ozcelik, H G; Sozen, Y; Sahin, H; Barisik, M Parametrizing nonbonded interactions between silica and water from first principles Journal Article Applied Surface Science, 504 , 2020, (cited By 2). @article{Ozcelik2020, title = {Parametrizing nonbonded interactions between silica and water from first principles}, author = {H G Ozcelik and Y Sozen and H Sahin and M Barisik}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075459998&doi=10.1016%2fj.apsusc.2019.144359&partnerID=40&md5=edc43d7aa69a9dad5f9eca3aca86e4fa}, doi = {10.1016/j.apsusc.2019.144359}, year = {2020}, date = {2020-01-01}, journal = {Applied Surface Science}, volume = {504}, note = {cited By 2}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Ozcelik, H G; Ozdemir, A C; Kim, B; Barisik, M Wetting of single crystalline and amorphous silicon surfaces: effective range of intermolecular forces for wetting Journal Article Molecular Simulation, 46 (3), pp. 224-234, 2020, (cited By 3). @article{Ozcelik2020224, title = {Wetting of single crystalline and amorphous silicon surfaces: effective range of intermolecular forces for wetting}, author = {H G Ozcelik and A C Ozdemir and B Kim and M Barisik}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075451686&doi=10.1080%2f08927022.2019.1690145&partnerID=40&md5=de3ea34b7359d5d74fbc29c3cd7ee7f6}, doi = {10.1080/08927022.2019.1690145}, year = {2020}, date = {2020-01-01}, journal = {Molecular Simulation}, volume = {46}, number = {3}, pages = {224-234}, note = {cited By 3}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
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. |
Kangal, S; Kartav, O; Tanoğlu, M; Aktaş, E; Artem, H S Journal of Composite Materials, 54 (7), pp. 961-980, 2020. @article{Kangal2020961, title = {Investigation of interlayer hybridization effect on burst pressure performance of composite overwrapped pressure vessels with load-sharing metallic liner}, author = {S Kangal and O Kartav and M Tanoğlu and E Aktaş and H S Artem}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071956589&doi=10.1177%2f0021998319870588&partnerID=40&md5=90d8ba513531b1cd09c963d447aebf4a}, doi = {10.1177/0021998319870588}, year = {2020}, date = {2020-01-01}, journal = {Journal of Composite Materials}, volume = {54}, number = {7}, pages = {961-980}, abstract = {In this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [±11°/90°2]3 to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic–plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers. © The Author(s) 2019.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [±11°/90°2]3 to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic–plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers. © The Author(s) 2019. |
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. |
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. |
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. |
Beylergil, B; Tanoǧlu, M; Aktaş, E Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils Journal Article Steel and Composite Structures, 31 (2), pp. 113-123, 2019. @article{Beylergil2019113, title = {Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils}, author = {B Beylergil and M Tanoǧlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065238224&doi=10.12989%2fscs.2019.31.2.113&partnerID=40&md5=c8783b96f972924d7754bb7820373a14}, doi = {10.12989/scs.2019.31.2.113}, year = {2019}, date = {2019-01-01}, journal = {Steel and Composite Structures}, volume = {31}, number = {2}, pages = {113-123}, abstract = {In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m 2 to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites. Copyright © 2019 Techno-Press, Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m 2 to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites. Copyright © 2019 Techno-Press, Ltd. |
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. |
Kandemir, S Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing Journal Article Journal of Materials Engineering and Performance, 27 (6), pp. 3014-3023, 2018. @article{Kandemir20183014, title = {Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046038152&doi=10.1007%2fs11665-018-3391-x&partnerID=40&md5=1915050ebdd364d0e0e99a6144a89c16}, doi = {10.1007/s11665-018-3391-x}, year = {2018}, date = {2018-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {27}, number = {6}, pages = {3014-3023}, abstract = {It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International. |
Kandemir, S Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing Journal Article Journal of Materials Engineering and Performance, 27 (6), pp. 3014-3023, 2018. @article{Kandemir20183014b, title = {Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046038152&doi=10.1007%2fs11665-018-3391-x&partnerID=40&md5=1915050ebdd364d0e0e99a6144a89c16}, doi = {10.1007/s11665-018-3391-x}, year = {2018}, date = {2018-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {27}, number = {6}, pages = {3014-3023}, abstract = {It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International. |
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. |
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. |
Oztoprak, N; Gunes, M D; Tanoglu, M; Aktas, E; Egilmez, O O; Senocak, C; Kulac, G Developing polymer composite-based leaf spring systems for automotive industry Journal Article Science and Engineering of Composite Materials, 25 (6), pp. 1167-1176, 2018. @article{Oztoprak20181167, title = {Developing polymer composite-based leaf spring systems for automotive industry}, author = {N Oztoprak and M D Gunes and M Tanoglu and E Aktas and O O Egilmez and C Senocak and G Kulac}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056594508&doi=10.1515%2fsecm-2016-0335&partnerID=40&md5=f8692f0ca38d12eec3006c474b120b21}, doi = {10.1515/secm-2016-0335}, year = {2018}, date = {2018-01-01}, journal = {Science and Engineering of Composite Materials}, volume = {25}, number = {6}, pages = {1167-1176}, abstract = {Composite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance. © 2018 Walter de Gruyter GmbH, Berlin/Boston.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Composite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance. © 2018 Walter de Gruyter GmbH, Berlin/Boston. |
Beylergil, B; Tanoğlu, M; Aktaş, E Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites Journal Article Composite Structures, 194 , pp. 21-35, 2018. @article{Beylergil201821, title = {Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites}, author = {B Beylergil and M Tanoğlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044992271&doi=10.1016%2fj.compstruct.2018.03.097&partnerID=40&md5=5a48cd887d9aa73061331019a3e6b047}, doi = {10.1016/j.compstruct.2018.03.097}, year = {2018}, date = {2018-01-01}, journal = {Composite Structures}, volume = {194}, pages = {21-35}, abstract = {In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness. © 2018}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness. © 2018 |
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} } |
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. |
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. |
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. |
Celebi, Alper Tunga; Barisik, Murat; Beskok, Ali Electric field controlled transport of water in graphene nano-channels Journal Article JOURNAL OF CHEMICAL PHYSICS, 147 (16), 2017, ISSN: 0021-9606. @article{ISI:000414177600067, title = {Electric field controlled transport of water in graphene nano-channels}, author = {Alper Tunga Celebi and Murat Barisik and Ali Beskok}, doi = {10.1063/1.4996210}, issn = {0021-9606}, year = {2017}, date = {2017-10-01}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {147}, number = {16}, abstract = {Motivated by electrowetting-based flow control in nano-systems, water transport in graphene nano-channels is investigated as a function of the applied electric field. Molecular dynamics simulations are performed for deionized water confined in graphene nano-channels subjected to opposing surface charges, creating an electric field across the channel. Water molecules respond to the electric field by reorientation of their dipoles. Oxygen and hydrogen atoms in water face the anode and cathode, respectively, and hydrogen atoms get closer to the cathode compared to the oxygen atoms near the anode. These effects create asymmetric density distributions that increase with the applied electric field. Force-driven water flows under electric fields exhibit asymmetric velocity profiles and unequal slip lengths. Apparent viscosity of water increases and the slip length decreases with increased electric field, reducing the flow rate. Increasing the electric field above a threshold value freezes water at room temperature. Published by AIP Publishing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Motivated by electrowetting-based flow control in nano-systems, water transport in graphene nano-channels is investigated as a function of the applied electric field. Molecular dynamics simulations are performed for deionized water confined in graphene nano-channels subjected to opposing surface charges, creating an electric field across the channel. Water molecules respond to the electric field by reorientation of their dipoles. Oxygen and hydrogen atoms in water face the anode and cathode, respectively, and hydrogen atoms get closer to the cathode compared to the oxygen atoms near the anode. These effects create asymmetric density distributions that increase with the applied electric field. Force-driven water flows under electric fields exhibit asymmetric velocity profiles and unequal slip lengths. Apparent viscosity of water increases and the slip length decreases with increased electric field, reducing the flow rate. Increasing the electric field above a threshold value freezes water at room temperature. Published by AIP Publishing. |
Kalyoncu, Gulce; Barisik, Murat Analytical solution of micro-/nanoscale convective liquid flows in tubes and slits Journal Article MICROFLUIDICS AND NANOFLUIDICS, 21 (9), 2017, ISSN: 1613-4982. @article{ISI:000410286400004, title = {Analytical solution of micro-/nanoscale convective liquid flows in tubes and slits}, author = {Gulce Kalyoncu and Murat Barisik}, doi = {10.1007/s10404-017-1985-5}, issn = {1613-4982}, year = {2017}, date = {2017-09-01}, journal = {MICROFLUIDICS AND NANOFLUIDICS}, volume = {21}, number = {9}, abstract = {Analytical solutions examining heat transport in micro-/nanoscale liquid flows were developed. Using the energy equation coupled with fully developed velocity, we solved developing temperature profiles with axial conduction and viscous dissipation terms. A comprehensive literature review provided the published range of velocity slip and temperature jump conditions. While molecular simulations and experiments present constant slip and jump values for a specific liquid/surface couple independent of confinement size, non-dimensional forms of these boundary conditions were found appropriate to calculate non-equilibrium as a function of flow height. Although slip and jump conditions are specific for each liquid/surface couple and hard to obtain, we proposed modeling of the slip and jump as a function of the surface wetting, in order to create a general, easy to measure methodology. We further developed possible correlations to calculate jump using the slip value of the corresponding surface and tested in the results. Fully developed Nu showed strong dependence on slip and jump. Heat transfer stopped when slip and jump coefficients became higher than a certain value. Strong variation of Nu in the thermal development length was observed for low slip and jump cases, while an almost constant Nu in the flow direction was found for high slip and jump coefficients. Variation of temperature profiles was found to dominate the heat transfer through the constant temperature surface while surface and liquid temperatures became equal at heat transfer lengths comparable with confinement sizes for no-dissipation cases. In case of non-negligible heat dissipation, viscous heating dominated the Nu value by enhancing the heating while decreasing the heat removal in cooling cases. Implementation of proposed procedure on a micro-channel convection problem from a micro-fluidics application showed the dominant effect of the model defining the slip and jump relationship. Direct use of kinetic gas theory resulted in an increase of Nu by an increase in non-equilibrium, while models developed from published liquid slip and jump values produced an opposite behavior.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Analytical solutions examining heat transport in micro-/nanoscale liquid flows were developed. Using the energy equation coupled with fully developed velocity, we solved developing temperature profiles with axial conduction and viscous dissipation terms. A comprehensive literature review provided the published range of velocity slip and temperature jump conditions. While molecular simulations and experiments present constant slip and jump values for a specific liquid/surface couple independent of confinement size, non-dimensional forms of these boundary conditions were found appropriate to calculate non-equilibrium as a function of flow height. Although slip and jump conditions are specific for each liquid/surface couple and hard to obtain, we proposed modeling of the slip and jump as a function of the surface wetting, in order to create a general, easy to measure methodology. We further developed possible correlations to calculate jump using the slip value of the corresponding surface and tested in the results. Fully developed Nu showed strong dependence on slip and jump. Heat transfer stopped when slip and jump coefficients became higher than a certain value. Strong variation of Nu in the thermal development length was observed for low slip and jump cases, while an almost constant Nu in the flow direction was found for high slip and jump coefficients. Variation of temperature profiles was found to dominate the heat transfer through the constant temperature surface while surface and liquid temperatures became equal at heat transfer lengths comparable with confinement sizes for no-dissipation cases. In case of non-negligible heat dissipation, viscous heating dominated the Nu value by enhancing the heating while decreasing the heat removal in cooling cases. Implementation of proposed procedure on a micro-channel convection problem from a micro-fluidics application showed the dominant effect of the model defining the slip and jump relationship. Direct use of kinetic gas theory resulted in an increase of Nu by an increase in non-equilibrium, while models developed from published liquid slip and jump values produced an opposite behavior. |
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. |
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. |
Cetkin, E VASCULAR STRUCTURES FOR SMART FEATURES: SELF-COOLING AND SELF-HEALING Journal Article JOURNAL OF THERMAL ENGINEERING, 3 (4, 5), pp. 1338-1345, 2017, ISSN: 2148-7847. @article{ISI:000407804200004, title = {VASCULAR STRUCTURES FOR SMART FEATURES: SELF-COOLING AND SELF-HEALING}, author = {E Cetkin}, doi = {10.18186/journal-of-thermal-engineering.330185}, issn = {2148-7847}, year = {2017}, date = {2017-08-01}, journal = {JOURNAL OF THERMAL ENGINEERING}, volume = {3}, number = {4, 5}, pages = {1338-1345}, abstract = {Here we show how smart features of self-cooling and self-healing can be gained to mechanical systems with embedded vascular structures. Vascular structures mimic the circulatory system of animals. Similar to blood distribution from heart to the animal body, vascular channels provide the distribution of coolant and/or healing agent from a point to the entire body of a mechanic system. Thus the mechanic system becomes capable of cooling itself under unpredictable heat attacks and capable of healing itself as cracks occur due to applied mechanical loads. These smart features are necessary for advanced devices, equipment and vehicles. The essential design parameter is vascularization in order to provide smart features. There are distinct configurations for vascularization such as radial, tree-shaped, grid and hybrids of these designs. In addition, several theories are available for the shape optimization of vascular structures such as fractal theory and constructal theory. Unlike fractal theory, constructal theory does not include constraints based on generic algorithms and dictated assumptions. Therefore, constructal theory approach is discussed in this paper. This paper shows how smart features can be gained to a mechanical system while its weight decreases and its mechanical strength increases simultaneously.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here we show how smart features of self-cooling and self-healing can be gained to mechanical systems with embedded vascular structures. Vascular structures mimic the circulatory system of animals. Similar to blood distribution from heart to the animal body, vascular channels provide the distribution of coolant and/or healing agent from a point to the entire body of a mechanic system. Thus the mechanic system becomes capable of cooling itself under unpredictable heat attacks and capable of healing itself as cracks occur due to applied mechanical loads. These smart features are necessary for advanced devices, equipment and vehicles. The essential design parameter is vascularization in order to provide smart features. There are distinct configurations for vascularization such as radial, tree-shaped, grid and hybrids of these designs. In addition, several theories are available for the shape optimization of vascular structures such as fractal theory and constructal theory. Unlike fractal theory, constructal theory does not include constraints based on generic algorithms and dictated assumptions. Therefore, constructal theory approach is discussed in this paper. This paper shows how smart features can be gained to a mechanical system while its weight decreases and its mechanical strength increases simultaneously. |
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} } |
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. |
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. |
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. |
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. |
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. |
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. |
Sahin, Osman Nuri; Uzunoglu, Emre; Tatlicioglu, Enver; Dede, Can M I Design and Development of an Educational Desktop Robot (RD)-D-3 Journal Article COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, 25 (2), pp. 222-229, 2017, ISSN: 1061-3773. @article{ISI:000401196200006, title = {Design and Development of an Educational Desktop Robot (RD)-D-3}, author = {Osman Nuri Sahin and Emre Uzunoglu and Enver Tatlicioglu and Can M I Dede}, doi = {10.1002/cae.21792}, issn = {1061-3773}, year = {2017}, date = {2017-03-01}, journal = {COMPUTER APPLICATIONS IN ENGINEERING EDUCATION}, volume = {25}, number = {2}, pages = {222-229}, abstract = {Robotic desktop devices have been used for academic purposes for a variety of investigation and development studies. Desktop devices for academic/educational purposes have been highly anticipated especially in the fields of haptics, teleoperation systems, and control studies. This paper's motivation is to present the steps of designing, manufacturing, and implementing of Educational Desktop Robot (RD)-D-3 to be used for haptics, teleoperation, and redundancy control studies. The design, manufacturing details, kinematic, and dynamic model of the robot are described in the manuscript. Additionally, a case study is carried out for end effector control in task space is given and the results are shared. (C) 2017 Wiley Periodicals, Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Robotic desktop devices have been used for academic purposes for a variety of investigation and development studies. Desktop devices for academic/educational purposes have been highly anticipated especially in the fields of haptics, teleoperation systems, and control studies. This paper's motivation is to present the steps of designing, manufacturing, and implementing of Educational Desktop Robot (RD)-D-3 to be used for haptics, teleoperation, and redundancy control studies. The design, manufacturing details, kinematic, and dynamic model of the robot are described in the manuscript. Additionally, a case study is carried out for end effector control in task space is given and the results are shared. (C) 2017 Wiley Periodicals, Inc. |
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. |
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} } |
Kandemir, S Journal of Composite Materials, 51 (3), pp. 395-404, 2017. @article{Kandemir2017395, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011573357&doi=10.1177%2f0021998316644850&partnerID=40&md5=1c26ba4dde5d58581fb0feb8fa56d880}, doi = {10.1177/0021998316644850}, year = {2017}, date = {2017-01-01}, journal = {Journal of Composite Materials}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5 wt.% 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 (20-30 nm) and aluminium powders (<75 μm) 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. © The Author(s) 2016.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5 wt.% 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 (20-30 nm) and aluminium powders (<75 μm) 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. © The Author(s) 2016. |
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. |
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. |
Kandemir, S Journal of Composite Materials, 51 (3), pp. 395-404, 2017. @article{Kandemir2017395b, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011573357&doi=10.1177%2f0021998316644850&partnerID=40&md5=1c26ba4dde5d58581fb0feb8fa56d880}, doi = {10.1177/0021998316644850}, year = {2017}, date = {2017-01-01}, journal = {Journal of Composite Materials}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5 wt.% 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 (20-30 nm) and aluminium powders (<75 μm) 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. © The Author(s) 2016.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5 wt.% 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 (20-30 nm) and aluminium powders (<75 μm) 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. © The Author(s) 2016. |
Tasdemirci, A; Tunusoglu, G JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS, 30 (1), pp. 88-106, 2017, ISSN: 0892-7057. @article{ISI:000397204900005, title = {Experimental and numerical investigation of the effect of interlayer on the damage formation in a ceramic/composite armor at a low projectile velocity}, author = {A Tasdemirci and G Tunusoglu}, doi = {10.1177/0892705715584410}, issn = {0892-7057}, year = {2017}, date = {2017-01-01}, journal = {JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS}, volume = {30}, number = {1}, pages = {88-106}, abstract = {The damage formation in a multilayered armor system without and with an interlayer (rubber, Teflon, and aluminum foam) between the front face ceramic layer and the composite backing plate were investigated experimentally and numerically. The projectile impact tests were performed in a low-velocity projectile impact test system and the numerical studies were implemented using the nonlinear finite element code LS-DYNA. The results of numerical simulations showed that the stress wave transmission to the composite backing plate decreased significantly in Teflon and foam interlayer armor configurations. Similar to without interlayer configuration, the rubber interlayer configuration led to the passage of relatively high stress waves to the composite backing plate. This was mainly attributed to the increased rubber interlayer impedance during the impact event. The numerical results of reduced stress wave transmission to the backing plate and the increased damage formation in the ceramic front face layer with the use of Teflon and foam interlayer was further confirmed experimentally.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The damage formation in a multilayered armor system without and with an interlayer (rubber, Teflon, and aluminum foam) between the front face ceramic layer and the composite backing plate were investigated experimentally and numerically. The projectile impact tests were performed in a low-velocity projectile impact test system and the numerical studies were implemented using the nonlinear finite element code LS-DYNA. The results of numerical simulations showed that the stress wave transmission to the composite backing plate decreased significantly in Teflon and foam interlayer armor configurations. Similar to without interlayer configuration, the rubber interlayer configuration led to the passage of relatively high stress waves to the composite backing plate. This was mainly attributed to the increased rubber interlayer impedance during the impact event. The numerical results of reduced stress wave transmission to the backing plate and the increased damage formation in the ceramic front face layer with the use of Teflon and foam interlayer was further confirmed experimentally. |
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. |
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. |
Beylergil, B; Tanoğlu, M; Aktaş, E 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. @article{Beylergil2017, title = {Enhancement of interlaminar fracture toughness of carbon fiber–epoxy composites using polyamide-6,6 electrospun nanofibers}, author = {B Beylergil and M Tanoğlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019089440&doi=10.1002%2fapp.45244&partnerID=40&md5=ef8bdba44c46b9b1bc9aaedfbbbde061}, doi = {10.1002/app.45244}, year = {2017}, date = {2017-01-01}, 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. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. © 2017 Wiley Periodicals, Inc.}, 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. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. © 2017 Wiley Periodicals, Inc. |
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. |
Kalyoncu, Gulce; Barisik, Murat The extended Graetz problem for micro-slit geometries; analytical coupling of rarefaction, axial conduction and viscous dissipation Journal Article INTERNATIONAL JOURNAL OF THERMAL SCIENCES, 110 , pp. 261-269, 2016, ISSN: 1290-0729. @article{ISI:000382793600021, title = {The extended Graetz problem for micro-slit geometries; analytical coupling of rarefaction, axial conduction and viscous dissipation}, author = {Gulce Kalyoncu and Murat Barisik}, doi = {10.1016/j.ijthermalsci.2016.07.009}, issn = {1290-0729}, year = {2016}, date = {2016-12-01}, journal = {INTERNATIONAL JOURNAL OF THERMAL SCIENCES}, volume = {110}, pages = {261-269}, abstract = {In order to support the recent MEMS and Lab-on-a-chip technologies, we studied heat transport in micro-scale slit channel gas flows. Since the micro convection transport phenomena diverges from conventional macro-scale transport due to rarefaction, axial conduction and viscous heating, an accurate understanding requires a complete coupling of these effects. For such cases, we studied heat transfer in hydrodynamically developed, thermally developing gas flows in micro-slits at various flow conditions. The analytical solution of the energy equation considered both the heat conduction in the axial direction and heat dissipation of viscous forces. Furthermore, updated boundary conditions of velocity slip and temperature jump were applied based on Knudsen number of flow in order to account for the non equilibrium gas dynamics. Local Nusselt number (Nu) values were calculated as a function of Peclet (Pe), Knudsen (Kn) and Brinkman (Br) numbers which were selected carefully according to possible micro-flow cases. Strong variation of Nu in thermal development length was found to dominate heat transfer behavior of micro-slits with short heating lengths for early slip flow regime. For this instance, influence of axial conduction and viscous dissipation was equally important. On the other hand, high Kn slip flow suppressed the axial conduction while viscous heating in a small surface-gas temperature difference case mostly determined the fully developed Nu and average heat transfer behavior as a function of Kn value. (C) 2016 Elsevier Masson SAS. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to support the recent MEMS and Lab-on-a-chip technologies, we studied heat transport in micro-scale slit channel gas flows. Since the micro convection transport phenomena diverges from conventional macro-scale transport due to rarefaction, axial conduction and viscous heating, an accurate understanding requires a complete coupling of these effects. For such cases, we studied heat transfer in hydrodynamically developed, thermally developing gas flows in micro-slits at various flow conditions. The analytical solution of the energy equation considered both the heat conduction in the axial direction and heat dissipation of viscous forces. Furthermore, updated boundary conditions of velocity slip and temperature jump were applied based on Knudsen number of flow in order to account for the non equilibrium gas dynamics. Local Nusselt number (Nu) values were calculated as a function of Peclet (Pe), Knudsen (Kn) and Brinkman (Br) numbers which were selected carefully according to possible micro-flow cases. Strong variation of Nu in thermal development length was found to dominate heat transfer behavior of micro-slits with short heating lengths for early slip flow regime. For this instance, influence of axial conduction and viscous dissipation was equally important. On the other hand, high Kn slip flow suppressed the axial conduction while viscous heating in a small surface-gas temperature difference case mostly determined the fully developed Nu and average heat transfer behavior as a function of Kn value. (C) 2016 Elsevier Masson SAS. All rights reserved. |
Yenigun, O; Cetkin, E Experimental and numerical investigation of constructal vascular channels for self-cooling: Parallel channels, tree-shaped and hybrid designs Journal Article INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 103 , pp. 1155-1165, 2016, ISSN: 0017-9310. @article{ISI:000384777800107b, title = {Experimental and numerical investigation of constructal vascular channels for self-cooling: Parallel channels, tree-shaped and hybrid designs}, author = {O Yenigun and E Cetkin}, doi = {10.1016/j.ijheatmasstransfer.2016.08.074}, issn = {0017-9310}, year = {2016}, date = {2016-12-01}, journal = {INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, volume = {103}, pages = {1155-1165}, abstract = {In this paper, we show experimentally and numerically how a plate which is subjected to a constant heat load can be kept under an allowable temperature limit. Vascular channels in which coolant fluid flows have been embedded in the plate. Three types of vascular channel designs were compared: parallel channels, tree-shaped and their hybrid. The effects of channel design on the thermal performance for different volume fractions (the fluid volume over the solid volume) are documented. In addition, the effects of the number of channels on cooling performance have been documented. Changing the design from parallel channels to tree-shaped designs decreases the order of pressure drop. Hence increase in the order of the convective heat transfer coefficient is achieved. However, tree-shaped designs do not bathe the entire domain, which increases the conductive resistances. Therefore, additional channels were inserted at the uncooled regions in the tree-shaped design (hybrid design). The best features of both parallel channels and tree-shaped designs are combined in the hybrid of them: the flow resistances to the fluid and heat flow become almost as low as the tree-shaped and parallel channels designs, respectively. The effect of design on the maximum temperature shows that there should be an optimum design for a distinct set of boundary conditions, and this design should be varied as the boundary conditions change. This result is in accord with the constructal law, i.e. the shape should be varied in order to minimize resistances to the flows. (C) 2016 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, we show experimentally and numerically how a plate which is subjected to a constant heat load can be kept under an allowable temperature limit. Vascular channels in which coolant fluid flows have been embedded in the plate. Three types of vascular channel designs were compared: parallel channels, tree-shaped and their hybrid. The effects of channel design on the thermal performance for different volume fractions (the fluid volume over the solid volume) are documented. In addition, the effects of the number of channels on cooling performance have been documented. Changing the design from parallel channels to tree-shaped designs decreases the order of pressure drop. Hence increase in the order of the convective heat transfer coefficient is achieved. However, tree-shaped designs do not bathe the entire domain, which increases the conductive resistances. Therefore, additional channels were inserted at the uncooled regions in the tree-shaped design (hybrid design). The best features of both parallel channels and tree-shaped designs are combined in the hybrid of them: the flow resistances to the fluid and heat flow become almost as low as the tree-shaped and parallel channels designs, respectively. The effect of design on the maximum temperature shows that there should be an optimum design for a distinct set of boundary conditions, and this design should be varied as the boundary conditions change. This result is in accord with the constructal law, i.e. the shape should be varied in order to minimize resistances to the flows. (C) 2016 Elsevier Ltd. All rights reserved. |
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. |
Kilicaslan, Cenk; Odaci, Ismet K; Gueden, Mustafa Single- and double-layer aluminum corrugated core sandwiches under quasi-static and dynamic loadings Journal Article JOURNAL OF SANDWICH STRUCTURES & MATERIALS, 18 (6), pp. 667-692, 2016, ISSN: 1099-6362. @article{ISI:000390061800001, title = {Single- and double-layer aluminum corrugated core sandwiches under quasi-static and dynamic loadings}, author = {Cenk Kilicaslan and Ismet K Odaci and Mustafa Gueden}, doi = {10.1177/1099636215603692}, issn = {1099-6362}, year = {2016}, date = {2016-11-01}, journal = {JOURNAL OF SANDWICH STRUCTURES & MATERIALS}, volume = {18}, number = {6}, pages = {667-692}, abstract = {The crushing of single- and double-layer zig-zag trapezoidal corrugated core sandwiches was investigated experimentally and numerically at quasi-static and dynamic rates. The buckling stress of sandwiches increased when the rate increased from quasi-static to dynamic. The increased buckling stresses were ascribed to the micro-inertial effects, which altered the buckling mode of the core from three plastic hinges to higher number of plastic hinge formations. The initial buckling stress was numerically shown to be imperfection sensitive when the imperfection size was comparable with the buckling length. The numerical buckling stresses of zig-zag and straight corrugated cores were similar, while higher inertial effects were found in triangular corrugated core.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The crushing of single- and double-layer zig-zag trapezoidal corrugated core sandwiches was investigated experimentally and numerically at quasi-static and dynamic rates. The buckling stress of sandwiches increased when the rate increased from quasi-static to dynamic. The increased buckling stresses were ascribed to the micro-inertial effects, which altered the buckling mode of the core from three plastic hinges to higher number of plastic hinge formations. The initial buckling stress was numerically shown to be imperfection sensitive when the imperfection size was comparable with the buckling length. The numerical buckling stresses of zig-zag and straight corrugated cores were similar, while higher inertial effects were found in triangular corrugated core. |
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). |
Sindirac, Can; Akkurt, Sedat Formation of La1-xSrxCo1-yFeyO3-delta cathode materials from precursor salts by heating in contact with CGO electrolyte Journal Article INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 41 (40), pp. 18157-18165, 2016, ISSN: 0360-3199. @article{ISI:000384852200041, title = {Formation of La1-xSrxCo1-yFeyO3-delta cathode materials from precursor salts by heating in contact with CGO electrolyte}, author = {Can Sindirac and Sedat Akkurt}, doi = {10.1016/j.ijhydene.2016.07.143}, issn = {0360-3199}, year = {2016}, date = {2016-10-01}, journal = {INTERNATIONAL JOURNAL OF HYDROGEN ENERGY}, volume = {41}, number = {40}, pages = {18157-18165}, abstract = {The purpose of this study is to determine the solid state reactions leading to the formation of La0.6Sr0.4Co0.8Fe0.2O3 and La0.6Sr0.4Co0.2Fe0.8O3 which are widely used as cathode material in solid oxide fuel cells (SOFC) from precursor salts. Interactions between the cathode and the electrolyte layers are also investigated while the cathode layer formed upon heating in contact with the surface of cerium -gadolinium oxide (CGO) electrolyte substrates. Almost all combinations of precursor salt mixtures were tested to see if all solid state reactions are completed and what phases eventually formed. Most of the transformation was complete after 1050 degrees C heat treatment to yield different mixed oxides. The cathode layer was usually in porous form but was found to spread well over the substrate. Uneven diffusion of La, Sr, Co or Fe into the substrate influenced the stoichiometry of the resulting cathode layer in varying degrees. Fe was found to diffuse into the substrate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The purpose of this study is to determine the solid state reactions leading to the formation of La0.6Sr0.4Co0.8Fe0.2O3 and La0.6Sr0.4Co0.2Fe0.8O3 which are widely used as cathode material in solid oxide fuel cells (SOFC) from precursor salts. Interactions between the cathode and the electrolyte layers are also investigated while the cathode layer formed upon heating in contact with the surface of cerium -gadolinium oxide (CGO) electrolyte substrates. Almost all combinations of precursor salt mixtures were tested to see if all solid state reactions are completed and what phases eventually formed. Most of the transformation was complete after 1050 degrees C heat treatment to yield different mixed oxides. The cathode layer was usually in porous form but was found to spread well over the substrate. Uneven diffusion of La, Sr, Co or Fe into the substrate influenced the stoichiometry of the resulting cathode layer in varying degrees. Fe was found to diffuse into the substrate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. |
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. |
Pham, An Truong; Barisik, Murat; Kim, BoHung Interfacial thermal resistance between the graphene-coated copper and liquid water Journal Article INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 97 , pp. 422-431, 2016, ISSN: 0017-9310. @article{ISI:000374616900038, title = {Interfacial thermal resistance between the graphene-coated copper and liquid water}, author = {An Truong Pham and Murat Barisik and BoHung Kim}, doi = {10.1016/j.ijheatmasstransfer.2016.02.040}, issn = {0017-9310}, year = {2016}, date = {2016-06-01}, journal = {INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, volume = {97}, pages = {422-431}, abstract = {The thermal coupling at water-solid interfaces is a key factor in controlling thermal resistance and the performance of nanoscale devices. This is especially important across the recently engineered nano-composite structures composed of a graphene-coated-metal surface. In this paper, a series of molecular dynamics simulations were conducted to investigate Kapitza length at the interface of liquid water and nano-composite surfaces of graphene-coated-Cu(111). We found that Kapitza length gradually increased and converged to the value measured on pure graphite surface with the increase of the number of graphene layers inserted on the Cu surface. Different than the earlier hypothesis on the ``transparency of graphene,'' the Kapitza length at the interface of mono-layer graphene coated Cu and water was found to be 2.5 times larger than the value of bare Cu surface. This drastic change of thermal resistance with the additional of a single graphene is validated by the surface energy calculations indicating that the mono-layer graphene allows only similar to 18% van der Waals energy of underneath Cu to transmit. We introduced an ``overall interaction strength'' value for the nano-composites based the quantitative contribution of pair interaction potentials of each material with water into the total surface energy in each case. Similar to earlier studies, results revealed that Kapitza length shows exponentially variation as a function of the estimated interaction strength of the nano-composite surfaces. The effect of Cu/graphene coupling on thermal behavior between the nano-composite with water was characterized. The Kapitza length was found to decrease significantly with increased Cu/graphene strength in the case of weak coupling, while this behavior becomes negligible with strong coupling of Cu and graphene. (C) 2016 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The thermal coupling at water-solid interfaces is a key factor in controlling thermal resistance and the performance of nanoscale devices. This is especially important across the recently engineered nano-composite structures composed of a graphene-coated-metal surface. In this paper, a series of molecular dynamics simulations were conducted to investigate Kapitza length at the interface of liquid water and nano-composite surfaces of graphene-coated-Cu(111). We found that Kapitza length gradually increased and converged to the value measured on pure graphite surface with the increase of the number of graphene layers inserted on the Cu surface. Different than the earlier hypothesis on the ``transparency of graphene,'' the Kapitza length at the interface of mono-layer graphene coated Cu and water was found to be 2.5 times larger than the value of bare Cu surface. This drastic change of thermal resistance with the additional of a single graphene is validated by the surface energy calculations indicating that the mono-layer graphene allows only similar to 18% van der Waals energy of underneath Cu to transmit. We introduced an ``overall interaction strength'' value for the nano-composites based the quantitative contribution of pair interaction potentials of each material with water into the total surface energy in each case. Similar to earlier studies, results revealed that Kapitza length shows exponentially variation as a function of the estimated interaction strength of the nano-composite surfaces. The effect of Cu/graphene coupling on thermal behavior between the nano-composite with water was characterized. The Kapitza length was found to decrease significantly with increased Cu/graphene strength in the case of weak coupling, while this behavior becomes negligible with strong coupling of Cu and graphene. (C) 2016 Elsevier Ltd. All rights reserved. |
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. |
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. |
Vo, Truong Quoc; Barisik, Murat; Kim, BoHung Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection Journal Article JOURNAL OF CHEMICAL PHYSICS, 144 (19), 2016, ISSN: 0021-9606. @article{ISI:000377712600039, title = {Atomic density effects on temperature characteristics and thermal transport at grain boundaries through a proper bin size selection}, author = {Truong Quoc Vo and Murat Barisik and BoHung Kim}, doi = {10.1063/1.4949763}, issn = {0021-9606}, year = {2016}, date = {2016-05-01}, journal = {JOURNAL OF CHEMICAL PHYSICS}, volume = {144}, number = {19}, abstract = {This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an accurate understanding of thermal characteristics at the GB can be formulated by selecting a proper bin size. Published by AIP Publishing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an accurate understanding of thermal characteristics at the GB can be formulated by selecting a proper bin size. Published by AIP Publishing. |
Basturk, S B; Tanoglu, M; Cankaya, M A; Egilmez, O O Dynamic behavior predictions of fiber-metal laminate/aluminum foam sandwiches under various explosive weights Journal Article JOURNAL OF SANDWICH STRUCTURES & MATERIALS, 18 (3), pp. 321-342, 2016, ISSN: 1099-6362. @article{ISI:000375128600003b, title = {Dynamic behavior predictions of fiber-metal laminate/aluminum foam sandwiches under various explosive weights}, author = {S B Basturk and M Tanoglu and M A Cankaya and O O Egilmez}, doi = {10.1177/1099636215603036}, issn = {1099-6362}, year = {2016}, date = {2016-05-01}, journal = {JOURNAL OF SANDWICH STRUCTURES & MATERIALS}, volume = {18}, number = {3}, pages = {321-342}, abstract = {Application of blast tests causes some problems to characterize the performance of panels due to the drastic conditions of explosive medium. Real test has high safety concerns and is not easily accessible because of its extra budget. Some approaches are needed for the preliminary predictions of dynamic characteristics of panels under blast loading conditions. In this study, the response of sandwiches under blast effect was evaluated by combining quasi-static experiments and computational blast test data. The primary aim is to relate the quasi-static panel analysis to dynamic blast load. Based on this idea, lightweight sandwich composites were subjected to quasi-static compression loading with a special test apparatus and the samples were assumed as single degree-of-freedom mass-spring systems to include dynamic effect. This approach provides a simpler way to simulate the blast loading over the surface of the panels and reveals the possible failure mechanisms without applying any explosives. Therefore the design of the panels can be revised by considering quasi-static test results. In this work, the peak deflections and survivabilities of sandwiches for various explosive weights were predicted based on the formulations reported in the literature. Major failure types were also identified and evaluated with respect to their thicknesses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Application of blast tests causes some problems to characterize the performance of panels due to the drastic conditions of explosive medium. Real test has high safety concerns and is not easily accessible because of its extra budget. Some approaches are needed for the preliminary predictions of dynamic characteristics of panels under blast loading conditions. In this study, the response of sandwiches under blast effect was evaluated by combining quasi-static experiments and computational blast test data. The primary aim is to relate the quasi-static panel analysis to dynamic blast load. Based on this idea, lightweight sandwich composites were subjected to quasi-static compression loading with a special test apparatus and the samples were assumed as single degree-of-freedom mass-spring systems to include dynamic effect. This approach provides a simpler way to simulate the blast loading over the surface of the panels and reveals the possible failure mechanisms without applying any explosives. Therefore the design of the panels can be revised by considering quasi-static test results. In this work, the peak deflections and survivabilities of sandwiches for various explosive weights were predicted based on the formulations reported in the literature. Major failure types were also identified and evaluated with respect to their thicknesses. |
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 |