A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produc...A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. The grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. The difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. The RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.展开更多
A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature...A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature on the residual stress of the coatings is investigated. Simulated results show that the realistic situation strongly affects the residual stress. To be specific,i) The main residual stress concentrates on the coatings prepared on YG8 substrate,and the residual stress and its gradient of the coatings are bigger than that of the substrate; ii) TiAlN and TiCN coatings have better resistance compression than that of TiN coatings in the same condition; iii) The improved multilayer structure of the gradient hard coatings produces weaker residual stress but higher anti-pressure of the substrate.展开更多
Carburized gears are widely used in geared machines such as wind turbines.Contact fatigue problems occur in engineering practice,reducing reliabilities of machines.Contact fatigue failures are related to many factors,...Carburized gears are widely used in geared machines such as wind turbines.Contact fatigue problems occur in engineering practice,reducing reliabilities of machines.Contact fatigue failures are related to many factors,such as gradients of mechanical properties of the hardening layer.In this work,an elastic-plastic contact model of a carburized gear is developed based on the finite element method to evaluate contact fatigue failure risk,considering variations in hardness and strength.The Dang Van multiaxial equivalent stress is calculated via Python coding within the Abaqus framework.The gradient of yield strength along the depth from case to core is considered.The concept of local material fatigue failure risk is defined to evaluate the probability of pitting failure.The effects of design factors,such as the case hardening depth(CHD),surface hardness,and contact pressure on fatigue failure risk,are studied.As the CHD increases or the surface hardness decreases,the risk of deep spalling failure reduces.The increase in surface hardness leads to a decreased risk of pitting failure,while the variation in CHD hardly affects the pitting failure risk.展开更多
基金supports from the National Natural Science Foundation of China (Grant No. 51301092)Pangu Foundation are acknowledged
文摘A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. The grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. The difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. The RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.
基金Supported by the National High Technology Research and Development Programme of China(No.2012AA09A203)Project of Sichuan Education Department(No.14ZA0321)
文摘A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature on the residual stress of the coatings is investigated. Simulated results show that the realistic situation strongly affects the residual stress. To be specific,i) The main residual stress concentrates on the coatings prepared on YG8 substrate,and the residual stress and its gradient of the coatings are bigger than that of the substrate; ii) TiAlN and TiCN coatings have better resistance compression than that of TiN coatings in the same condition; iii) The improved multilayer structure of the gradient hard coatings produces weaker residual stress but higher anti-pressure of the substrate.
基金the National Basic Research Program of China(973 Program)(Grant No.2018YFB2001300)the National Natural Science Foundation of China(Grant No.51975063).
文摘Carburized gears are widely used in geared machines such as wind turbines.Contact fatigue problems occur in engineering practice,reducing reliabilities of machines.Contact fatigue failures are related to many factors,such as gradients of mechanical properties of the hardening layer.In this work,an elastic-plastic contact model of a carburized gear is developed based on the finite element method to evaluate contact fatigue failure risk,considering variations in hardness and strength.The Dang Van multiaxial equivalent stress is calculated via Python coding within the Abaqus framework.The gradient of yield strength along the depth from case to core is considered.The concept of local material fatigue failure risk is defined to evaluate the probability of pitting failure.The effects of design factors,such as the case hardening depth(CHD),surface hardness,and contact pressure on fatigue failure risk,are studied.As the CHD increases or the surface hardness decreases,the risk of deep spalling failure reduces.The increase in surface hardness leads to a decreased risk of pitting failure,while the variation in CHD hardly affects the pitting failure risk.
