Focus variation measurement and prediction of surface texture parameters using machine learning in laser powder bed fusion
Journal of Manufacturing Science and Engineering
The powder bed fusion based additive manufacturing process uses a laser to melt and fuse powder m... more The powder bed fusion based additive manufacturing process uses a laser to melt and fuse powder metal material together and creates parts with intricate surface topography that are often influenced by laser path, layer-to-layer scanning strategies, and energy density. Surface topography investigations of as-built, nickel alloy (625) surfaces were performed by obtaining areal height maps using focus variation microscopy for samples produced at various energy density settings and two different scan strategies. Surface areal height maps and measured surface texture parameters revealed highly irregular nature of surface topography created by laser powder bed fusion (LPBF). Effects of process parameters and energy density on the areal surface texture have been identified. Machine learning methods were applied to measured data to establish input and output relationships between process parameters and measured surface texture parameters with predictive capabilities. The advantages of utili...
Background : Modification of titanium dental implants are of great interest to enhance osseointeg... more Background : Modification of titanium dental implants are of great interest to enhance osseointegration and may provide successful long-term results. Boron nitride (BN), with its physical properties and beneficial effects on bone formation and composition, can be a promising material as a coating substance Aim/Hypothesis : The aim of this study was to evaluate osseointegration of BN coated implants both histomorphometrically and biomechanically on a rabbit model. BN has been coated two different coating thicknesses by using RF magnetron sputtering system. Material and Methods : Totally fifty-four implants were inserted into the tibias' of 12 New Zealand rabbits. Implants were placed bilaterally into the tibias under general anesthesia. All animals were sacrificed using intravenous sodium pentobarbital after 4 weeks. For the implants used for histomorphometric evaluation, bone-implant contact (BIC) percentages and new bone area total area (BATA) were calculated. The removal torque (RT) test was performed and the highest removal torque required for creating a fracture between the implant and bone was measured. Results : As a result of histomorphometric evaluations, the highest BIC percentages were observed in the control group, whereas the micro scale (micro-coated) BN group had a lower but comparable BIC level with the control group. In the nano-scale (nano-coated) BN group, the BIC percentages were low. The bone tissue in the medullary cavity was the highest in the micro-scale BN group, whereas the lowest values were observed in the control group. The RT values measured in all groups were found low, but the highest RT values torque was observed in the control group. Conclusion and Clinical Implications : As a result, no inflammatory problem developed around any implant. Osseointegration occurred around all control and BN-coated implants.
Models of solar-thermal powered adsorption cooling systems with and without heat recovery develop... more Models of solar-thermal powered adsorption cooling systems with and without heat recovery developed in TRNSYS and results from steady-periodic and seasonal simulations are presented. A normalized model is presented and used to process the seasonal TRNSYS results to investigate the coincidence between the solar-supplied cooling power and cooling load as the relative sizes of the cooling system and storage are varied. The normalized model yields a seasonal solar fraction and seasonal loss fraction (the excess solar-supplied cooling lost to the environment due to insufficient storage). Simulations were run for a zeolite-water adsorbent-refrigerant pair. Hourly weather data for Antalya, Turkey, were used for the transient simulations. Basic trends in performance were investigated as the following parameters were varied: system type (with or without heat recovery); incident radiation; maximum and minimum bed temperatures; condensation temperature; difference between condensation and minimum bed temperatures (bed excess temperature); bed's dead mass; collector type (flat plate vs. evacuated tube); cooling tower type (wet vs. dry); cooling system size; and, storage size. Results for the conditions explored include the following. Steady-periodic simulations show that the system's COP decreases with decreases in radiation and increases with minimum bed and condensation temperatures. Increasing the excess bed temperature increases the system's COP. Systems with an evacuated tube collector and wet cooling tower give higher system COP's than systems with a flat plate collector and dry cooling tower. The increase in system's COP due to decreasing the bed's dead mass and adding heat recovery is quantified. The solar fraction increases and the loss fraction decreases with increases in storage capacity, and both fractions decrease with increases in maximum bed temperature. The required evacuated tube collector area is smaller than the flat plate collector area while the required mass of adsorbent is independent of collector and adsorption cycle types.
... Otomotiv sanayindeki yaşanan bu süreç, beyaz eşya, elektrik-elektronik ve savunma sektöründe ... more ... Otomotiv sanayindeki yaşanan bu süreç, beyaz eşya, elektrik-elektronik ve savunma sektöründe de yaşanmıştır. ... Türkiye‟de 1990 yılında ODTÜ‟de KOSGEB desteği ile kurulan YenilikçilikMerkezi (Innovation Center) bir yeni ürün geliştirmek için fikri olanlar, ancak parası ve ...
Models of solar-thermal powered adsorption cooling systems with and without heat recovery develop... more Models of solar-thermal powered adsorption cooling systems with and without heat recovery developed in TRNSYS and results from steady-periodic and seasonal simulations are presented. A normalized model is presented and used to process the seasonal TRNSYS results to investigate the coincidence between the solar-supplied cooling power and cooling load as the relative sizes of the cooling system and storage are varied. The normalized model yields a seasonal solar fraction and seasonal loss fraction (the excess solar-supplied cooling lost to the environment due to insufficient storage). Simulations were run for a zeolite-water adsorbent-refrigerant pair. Hourly weather data for Antalya, Turkey, were used for the transient simulations. Basic trends in performance were investigated as the following parameters were varied: system type (with or without heat recovery); incident radiation; maximum and minimum bed temperatures; condensation temperature; difference between condensation and mini...
The theoretical performance of a solar-powered adsorption cooling system is investigated using TR... more The theoretical performance of a solar-powered adsorption cooling system is investigated using TRNSYS and Matlab. Adsorption models for several adsorbent-refrigerant pairs are integrated into previously developed adsorption cycle models. Seasonal transient simulations were run using these models and the actual weather data of Antalya, Turkey. Four cycle types, five working pairs and five parameters were investigated parametrically to determine the most appropriate adsorbent-refrigerant working pair and operating conditions for the Mediterranean region of Turkey, especially Antalya. Results are presented in terms of values and ratios of cooling capacity weighted COP. For the conditions explored, the thermal wave cycle, wet cooling towers and high evaporation temperatures produced the highest COP values. Additionally, each working pair has a distinct operating temperature range; therefore their selection should depend on the temperature of the available heat source (solar energy in th...
Moving part recognition and automatic pick and place using an industrial robot
Proceedings of the 1997 IEEE/RSJ International Conference on Intelligent Robot and Systems. Innovative Robotics for Real-World Applications. IROS '97, 1997
KES'2000. Fourth International Conference on Knowledge-Based Intelligent Engineering Systems and Allied Technologies. Proceedings (Cat. No.00TH8516), 2000
This paper presents a cost-eficient end-effector based infiared proximity sensor integration syst... more This paper presents a cost-eficient end-effector based infiared proximity sensor integration system and the implementation of fuzzy-logic control algorithm. End-effector sensor outputs are incorporated in a fuzzylogic control algorithm to make the robotic manipulator grasp objects on a moving conveyor belt. The robot movements are going to be the result of the comparative measurements made by the sensors after the motion of the moving target is predicted and the gripper is brought into a zone close to the object to be grasped by the application of a vision system.
Effect of hardening models on different ductile fracture criteria in sheet metal forming
International Journal of Material Forming, 2014
ABSTRACT Prediction of the fracture is one of the challenging issues which gains attention in she... more ABSTRACT Prediction of the fracture is one of the challenging issues which gains attention in sheet metal forming as numerical analyses are being extensively used to simulate the process. To have better results in predicting the sheet metal fracture, appropriate ductile fracture criterion (DFC), yield criterion and hardening rule should be chosen. In this study, the effects of different hardening models namely isotropic, kinematic and combined hardening rules on the various uncoupled ductile fracture criteria are investigated using experimental and numerical methods. Five different ductile fracture criteria are implemented to a finite element code by the user subroutines. The criterion constants of DFCs are obtained by the related experimental tests. The in-plane principle strains obtained by the finite element analyses for different DFCs are compared with the experimental results. Also, the experimental results are used to evaluate the principle strain values calculated by the finite element analysis for different combinations of DFCs and hardening rules. It is shown that some DFCs give better predictions if the appropriate hardening model is employed.
A new normalized model is developed to quantify and explore trends in coincidence of supply and d... more A new normalized model is developed to quantify and explore trends in coincidence of supply and demand in generic intermittent energy systems as key design and operating parameters are varied. This novel model is applied to seasonal-transient simulations for a solar-thermal powered adsorption system with and without heat recovery to investigate the coincidence between the solar-supplied cooling power and cooling load in terms of seasonal solar and loss fractions. Additionally, the system's basic performance trends are investigated as a number of parameters are varied. Results for the conditions explored include the following. The solar fraction increases and the loss fraction decreases with increases in storage capacity, and both fractions decrease with increases in maximum bed temperature. The required evacuated tube collector area is smaller than the flat plate collector area while the required mass of adsorbent is independent of collector and adsorption cycle types. Simulation results also show the effects of operating conditions and several design parameters on the system's COP.
Focus variation measurement and prediction of surface texture parameters using machine learning in laser powder bed fusion
Journal of Manufacturing Science and Engineering
The powder bed fusion based additive manufacturing process uses a laser to melt and fuse powder m... more The powder bed fusion based additive manufacturing process uses a laser to melt and fuse powder metal material together and creates parts with intricate surface topography that are often influenced by laser path, layer-to-layer scanning strategies, and energy density. Surface topography investigations of as-built, nickel alloy (625) surfaces were performed by obtaining areal height maps using focus variation microscopy for samples produced at various energy density settings and two different scan strategies. Surface areal height maps and measured surface texture parameters revealed highly irregular nature of surface topography created by laser powder bed fusion (LPBF). Effects of process parameters and energy density on the areal surface texture have been identified. Machine learning methods were applied to measured data to establish input and output relationships between process parameters and measured surface texture parameters with predictive capabilities. The advantages of utili...
Background : Modification of titanium dental implants are of great interest to enhance osseointeg... more Background : Modification of titanium dental implants are of great interest to enhance osseointegration and may provide successful long-term results. Boron nitride (BN), with its physical properties and beneficial effects on bone formation and composition, can be a promising material as a coating substance Aim/Hypothesis : The aim of this study was to evaluate osseointegration of BN coated implants both histomorphometrically and biomechanically on a rabbit model. BN has been coated two different coating thicknesses by using RF magnetron sputtering system. Material and Methods : Totally fifty-four implants were inserted into the tibias' of 12 New Zealand rabbits. Implants were placed bilaterally into the tibias under general anesthesia. All animals were sacrificed using intravenous sodium pentobarbital after 4 weeks. For the implants used for histomorphometric evaluation, bone-implant contact (BIC) percentages and new bone area total area (BATA) were calculated. The removal torque (RT) test was performed and the highest removal torque required for creating a fracture between the implant and bone was measured. Results : As a result of histomorphometric evaluations, the highest BIC percentages were observed in the control group, whereas the micro scale (micro-coated) BN group had a lower but comparable BIC level with the control group. In the nano-scale (nano-coated) BN group, the BIC percentages were low. The bone tissue in the medullary cavity was the highest in the micro-scale BN group, whereas the lowest values were observed in the control group. The RT values measured in all groups were found low, but the highest RT values torque was observed in the control group. Conclusion and Clinical Implications : As a result, no inflammatory problem developed around any implant. Osseointegration occurred around all control and BN-coated implants.
Models of solar-thermal powered adsorption cooling systems with and without heat recovery develop... more Models of solar-thermal powered adsorption cooling systems with and without heat recovery developed in TRNSYS and results from steady-periodic and seasonal simulations are presented. A normalized model is presented and used to process the seasonal TRNSYS results to investigate the coincidence between the solar-supplied cooling power and cooling load as the relative sizes of the cooling system and storage are varied. The normalized model yields a seasonal solar fraction and seasonal loss fraction (the excess solar-supplied cooling lost to the environment due to insufficient storage). Simulations were run for a zeolite-water adsorbent-refrigerant pair. Hourly weather data for Antalya, Turkey, were used for the transient simulations. Basic trends in performance were investigated as the following parameters were varied: system type (with or without heat recovery); incident radiation; maximum and minimum bed temperatures; condensation temperature; difference between condensation and minimum bed temperatures (bed excess temperature); bed's dead mass; collector type (flat plate vs. evacuated tube); cooling tower type (wet vs. dry); cooling system size; and, storage size. Results for the conditions explored include the following. Steady-periodic simulations show that the system's COP decreases with decreases in radiation and increases with minimum bed and condensation temperatures. Increasing the excess bed temperature increases the system's COP. Systems with an evacuated tube collector and wet cooling tower give higher system COP's than systems with a flat plate collector and dry cooling tower. The increase in system's COP due to decreasing the bed's dead mass and adding heat recovery is quantified. The solar fraction increases and the loss fraction decreases with increases in storage capacity, and both fractions decrease with increases in maximum bed temperature. The required evacuated tube collector area is smaller than the flat plate collector area while the required mass of adsorbent is independent of collector and adsorption cycle types.
... Otomotiv sanayindeki yaşanan bu süreç, beyaz eşya, elektrik-elektronik ve savunma sektöründe ... more ... Otomotiv sanayindeki yaşanan bu süreç, beyaz eşya, elektrik-elektronik ve savunma sektöründe de yaşanmıştır. ... Türkiye‟de 1990 yılında ODTÜ‟de KOSGEB desteği ile kurulan YenilikçilikMerkezi (Innovation Center) bir yeni ürün geliştirmek için fikri olanlar, ancak parası ve ...
Models of solar-thermal powered adsorption cooling systems with and without heat recovery develop... more Models of solar-thermal powered adsorption cooling systems with and without heat recovery developed in TRNSYS and results from steady-periodic and seasonal simulations are presented. A normalized model is presented and used to process the seasonal TRNSYS results to investigate the coincidence between the solar-supplied cooling power and cooling load as the relative sizes of the cooling system and storage are varied. The normalized model yields a seasonal solar fraction and seasonal loss fraction (the excess solar-supplied cooling lost to the environment due to insufficient storage). Simulations were run for a zeolite-water adsorbent-refrigerant pair. Hourly weather data for Antalya, Turkey, were used for the transient simulations. Basic trends in performance were investigated as the following parameters were varied: system type (with or without heat recovery); incident radiation; maximum and minimum bed temperatures; condensation temperature; difference between condensation and mini...
The theoretical performance of a solar-powered adsorption cooling system is investigated using TR... more The theoretical performance of a solar-powered adsorption cooling system is investigated using TRNSYS and Matlab. Adsorption models for several adsorbent-refrigerant pairs are integrated into previously developed adsorption cycle models. Seasonal transient simulations were run using these models and the actual weather data of Antalya, Turkey. Four cycle types, five working pairs and five parameters were investigated parametrically to determine the most appropriate adsorbent-refrigerant working pair and operating conditions for the Mediterranean region of Turkey, especially Antalya. Results are presented in terms of values and ratios of cooling capacity weighted COP. For the conditions explored, the thermal wave cycle, wet cooling towers and high evaporation temperatures produced the highest COP values. Additionally, each working pair has a distinct operating temperature range; therefore their selection should depend on the temperature of the available heat source (solar energy in th...
Moving part recognition and automatic pick and place using an industrial robot
Proceedings of the 1997 IEEE/RSJ International Conference on Intelligent Robot and Systems. Innovative Robotics for Real-World Applications. IROS '97, 1997
KES'2000. Fourth International Conference on Knowledge-Based Intelligent Engineering Systems and Allied Technologies. Proceedings (Cat. No.00TH8516), 2000
This paper presents a cost-eficient end-effector based infiared proximity sensor integration syst... more This paper presents a cost-eficient end-effector based infiared proximity sensor integration system and the implementation of fuzzy-logic control algorithm. End-effector sensor outputs are incorporated in a fuzzylogic control algorithm to make the robotic manipulator grasp objects on a moving conveyor belt. The robot movements are going to be the result of the comparative measurements made by the sensors after the motion of the moving target is predicted and the gripper is brought into a zone close to the object to be grasped by the application of a vision system.
Effect of hardening models on different ductile fracture criteria in sheet metal forming
International Journal of Material Forming, 2014
ABSTRACT Prediction of the fracture is one of the challenging issues which gains attention in she... more ABSTRACT Prediction of the fracture is one of the challenging issues which gains attention in sheet metal forming as numerical analyses are being extensively used to simulate the process. To have better results in predicting the sheet metal fracture, appropriate ductile fracture criterion (DFC), yield criterion and hardening rule should be chosen. In this study, the effects of different hardening models namely isotropic, kinematic and combined hardening rules on the various uncoupled ductile fracture criteria are investigated using experimental and numerical methods. Five different ductile fracture criteria are implemented to a finite element code by the user subroutines. The criterion constants of DFCs are obtained by the related experimental tests. The in-plane principle strains obtained by the finite element analyses for different DFCs are compared with the experimental results. Also, the experimental results are used to evaluate the principle strain values calculated by the finite element analysis for different combinations of DFCs and hardening rules. It is shown that some DFCs give better predictions if the appropriate hardening model is employed.
A new normalized model is developed to quantify and explore trends in coincidence of supply and d... more A new normalized model is developed to quantify and explore trends in coincidence of supply and demand in generic intermittent energy systems as key design and operating parameters are varied. This novel model is applied to seasonal-transient simulations for a solar-thermal powered adsorption system with and without heat recovery to investigate the coincidence between the solar-supplied cooling power and cooling load in terms of seasonal solar and loss fractions. Additionally, the system's basic performance trends are investigated as a number of parameters are varied. Results for the conditions explored include the following. The solar fraction increases and the loss fraction decreases with increases in storage capacity, and both fractions decrease with increases in maximum bed temperature. The required evacuated tube collector area is smaller than the flat plate collector area while the required mass of adsorbent is independent of collector and adsorption cycle types. Simulation results also show the effects of operating conditions and several design parameters on the system's COP.
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