Residual stress distributions in 7075 aluminum alloy thick plates with different thicknesses and different quenching speeds were measured. A shape function of stress distribution was proposed based on the internal str...Residual stress distributions in 7075 aluminum alloy thick plates with different thicknesses and different quenching speeds were measured. A shape function of stress distribution was proposed based on the internal stress distribution characteristics of aluminum alloy. Using nonlinear regression technology,the function between stress value of key points on internal stress curve and surface stress of the plate was obtained. Based on the measured surface stress,stress value of key points and stress distribution shape,the internal stress distribution can be reconstructed. The experiments show that the model is of good engineering practicality.展开更多
Shot peening is commonly employed for surface deformation strengthening of cylindrical surface part.Therefore,it is critical to understand the effects of shot peening on residual stress and surface topography.Compared...Shot peening is commonly employed for surface deformation strengthening of cylindrical surface part.Therefore,it is critical to understand the effects of shot peening on residual stress and surface topography.Compared to flat surface,cylindrical surface shot peening has two significant features:(i)the curvature of the cylindrical surface and the scattering of the shot stream cause dis-tributed impact velocities;(i)the rotation of the part results in a periodic variation of the impact velocity component.Therefore,it is a challenge to quickly and accurately predict the shot peening residual stress and surface topography of cylindrical surface.This paper developed a high-precision model which considers the more realistic shot peening process.Firstly,a kinematic analysis model was developed to simulate the relative movement of numerous shots and cylindrical surface.Then,the spatial distribution and time-varying impact information was calculated.Subsequently,the impact information was used for finite element modeling to predict residual stress and surface topography.The proposed kinematic analysis method was validated by comparison with the dis-crete element method.Meanwhile,9310 high strength steel rollers shot peening test verified the effectiveness of the model in predicting the residual stress and surface topography.In addition,the effects of air pressure and attack angle on the residual stress and surface topography were investigated.This work could provide a functional package for efficient prediction of the surface integrity and guide industrial application in cylindrical surface shot peening.展开更多
Surface integrity is important to improve the fatigue property of components.Proper selection of the cutting parameters is extremely important in ensuring high surface integrity.In this paper,ball end milling of TC17 ...Surface integrity is important to improve the fatigue property of components.Proper selection of the cutting parameters is extremely important in ensuring high surface integrity.In this paper,ball end milling of TC17 alloy has been carried out utilizing response surface methodology.The effects of cutting speed,feed per tooth,cutting depth,and cutting width on the surface integrity characteristics,including surface roughness(R_(a)),surface topography,residual stress,and microstructure were examined.Moreover,predictive metamodels for surface roughness,residual stress,and microhardness as a function of milling parameters were proposed.According to the experimental results obtained,the surface roughness increases with the increase of milling parameters,the(R_(a))values vary from 0.4μm to 1.2μm along the feed direction,which are much lower compared to that along the pick feed direction.The surface compressive residual stress increases with the increase of feed per tooth,cutting depth,and cutting width,while that decreases at high cutting speed.The depth of the compressive residual stress layer is mostly in the range of 25-40μm.The milled surface microhardness represents 6.4% compared with the initial state;the work-hardened layer depth is approximately 20μm.Moreover,plastic deformation and strain streamlines are observed within 3μm depth beneath the surface.The empirical model of surface integrity characteristics is developed using the results of ten experiments and validated by two extra experiments.The prediction errors of the three surface integrity characteristics are within 27%;the empirical model of microhardness has the lowest prediction errors.展开更多
Residual stress during the machining process has always been a research hotspot,especially for aero-engine blades.The three-dimensional modeling and reconstructive laws of residual stress among various processes in th...Residual stress during the machining process has always been a research hotspot,especially for aero-engine blades.The three-dimensional modeling and reconstructive laws of residual stress among various processes in the machining process of the fan blade is studied in this paper.The fan blades of Ti-6Al-4V are targeted for milling,polishing,heat treatment,vibratory finishing,and shot peening.The surface and subsurface residual stress after each process is measured by the X-ray diffraction method.The distribution of the surface and subsurface residual stress is analyzed.The Rational Taylor surface function and cosine decay function are used to fit the characteristic function of the residual stress distribution,and the empirical formula with high fitting accuracy is obtained.The value and distribution of surface and subsurface residual stress vary greatly due to different processing techniques.The reconstructive change of the surface and subsurface residual stress of the blade in each process intuitively shows the change of the residual stress between the processes,which has a high reference significance for the research on the residual stress of the blade processing and the optimization of the entire blade process.展开更多
基金Projects(2005CB623708, 2010CB731703) supported by the National Basic Research Program of China
文摘Residual stress distributions in 7075 aluminum alloy thick plates with different thicknesses and different quenching speeds were measured. A shape function of stress distribution was proposed based on the internal stress distribution characteristics of aluminum alloy. Using nonlinear regression technology,the function between stress value of key points on internal stress curve and surface stress of the plate was obtained. Based on the measured surface stress,stress value of key points and stress distribution shape,the internal stress distribution can be reconstructed. The experiments show that the model is of good engineering practicality.
基金the National Natural Science Foundation of China (No.U22B2086)the National Science and Technology Major Project through (No.2019-VII-0017-0158).
文摘Shot peening is commonly employed for surface deformation strengthening of cylindrical surface part.Therefore,it is critical to understand the effects of shot peening on residual stress and surface topography.Compared to flat surface,cylindrical surface shot peening has two significant features:(i)the curvature of the cylindrical surface and the scattering of the shot stream cause dis-tributed impact velocities;(i)the rotation of the part results in a periodic variation of the impact velocity component.Therefore,it is a challenge to quickly and accurately predict the shot peening residual stress and surface topography of cylindrical surface.This paper developed a high-precision model which considers the more realistic shot peening process.Firstly,a kinematic analysis model was developed to simulate the relative movement of numerous shots and cylindrical surface.Then,the spatial distribution and time-varying impact information was calculated.Subsequently,the impact information was used for finite element modeling to predict residual stress and surface topography.The proposed kinematic analysis method was validated by comparison with the dis-crete element method.Meanwhile,9310 high strength steel rollers shot peening test verified the effectiveness of the model in predicting the residual stress and surface topography.In addition,the effects of air pressure and attack angle on the residual stress and surface topography were investigated.This work could provide a functional package for efficient prediction of the surface integrity and guide industrial application in cylindrical surface shot peening.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.92160301,91860206,51875472,51905440)the National Science and Technology Major Project of China(Grant Nos.2017-VII-0001-0094,2017-VII-0005-0098).
文摘Surface integrity is important to improve the fatigue property of components.Proper selection of the cutting parameters is extremely important in ensuring high surface integrity.In this paper,ball end milling of TC17 alloy has been carried out utilizing response surface methodology.The effects of cutting speed,feed per tooth,cutting depth,and cutting width on the surface integrity characteristics,including surface roughness(R_(a)),surface topography,residual stress,and microstructure were examined.Moreover,predictive metamodels for surface roughness,residual stress,and microhardness as a function of milling parameters were proposed.According to the experimental results obtained,the surface roughness increases with the increase of milling parameters,the(R_(a))values vary from 0.4μm to 1.2μm along the feed direction,which are much lower compared to that along the pick feed direction.The surface compressive residual stress increases with the increase of feed per tooth,cutting depth,and cutting width,while that decreases at high cutting speed.The depth of the compressive residual stress layer is mostly in the range of 25-40μm.The milled surface microhardness represents 6.4% compared with the initial state;the work-hardened layer depth is approximately 20μm.Moreover,plastic deformation and strain streamlines are observed within 3μm depth beneath the surface.The empirical model of surface integrity characteristics is developed using the results of ten experiments and validated by two extra experiments.The prediction errors of the three surface integrity characteristics are within 27%;the empirical model of microhardness has the lowest prediction errors.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.51875472,91860206,and 51905440)the National Science and Technology Major Project(Grant No.2017-VII-0001-0094)+1 种基金the National Key Research and Development Plan in Shaanxi Province of China(Grant No.2019ZDLGY02-03)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2020JQ-186).
文摘Residual stress during the machining process has always been a research hotspot,especially for aero-engine blades.The three-dimensional modeling and reconstructive laws of residual stress among various processes in the machining process of the fan blade is studied in this paper.The fan blades of Ti-6Al-4V are targeted for milling,polishing,heat treatment,vibratory finishing,and shot peening.The surface and subsurface residual stress after each process is measured by the X-ray diffraction method.The distribution of the surface and subsurface residual stress is analyzed.The Rational Taylor surface function and cosine decay function are used to fit the characteristic function of the residual stress distribution,and the empirical formula with high fitting accuracy is obtained.The value and distribution of surface and subsurface residual stress vary greatly due to different processing techniques.The reconstructive change of the surface and subsurface residual stress of the blade in each process intuitively shows the change of the residual stress between the processes,which has a high reference significance for the research on the residual stress of the blade processing and the optimization of the entire blade process.
