Study On Residual Stress Field And Fatigue Life Of Titanium Alloy Shot Peening

As a metal material with high strength and high corrosion resistance,titanium alloy is widely used in the manufacture of aircraft engine blades.Its harsh operating conditions require higher strength and durability.Shot peening technology is a technology that performs impact processing on the surface of the material by spraying high-speed projectiles,which can enhance the surface hardness and fatigue resistance of the material,which plays an important role in improving the performance of aero-engine blades.In this paper,a random multi-projectile shot peening strengthening model was established by FEM-DEM coupling method,and the influence of process parameters on shot peening effect and fatigue life was studied by numerical simulation and experimental methods using TC4 titanium alloy as the research object.The main contents are as follows:1.The EM-DEM coupled multi-projectile shot peening strengthening model with single projectile,random probability distribution multiprojectile and more close to the actual shot peening process was established.The shot peening experiment of TC4 titanium alloy specimen was carried out,and the residual stress and surface roughness of the specimen under different shot peening strength and coverage were measured by X-ray diffraction method and roughness meter,which verified the reliability of FEM-DEM coupled multi-projectile shot peening strengthening model.2.Based on the FEM-DEM coupled shot peening model,the influence of different process parameters and blade surface curvature characteristics on the residual stress field and surface roughness of TC4 titanium alloy after shot peening was studied.The results show that the process parameters(projectile diameter,shot peening speed and shot peening coverage)can obtain better residual stress distribution by increasing within a certain range,but after reaching a certain value,the residual stress field is close to saturation and the surface roughness is large.A large surface curvature will make the shot peening effect poor,and the residual stress field depth will be shallow,while the shot peening strengthening effect is better when the curvature is smoother.3.Considering the correlation and interaction between different process parameters,a response surface prediction model between shot peening process parameters and shot peening strengthening effect is established,and the effectiveness of the established model is proved through the significance of the model,accuracy and signal-to-noise ratio,which can be used to quickly predict the shot peening effect.4.Considering the residual stress after shot peening,the fatigue life prediction model of TC4 titanium alloy was established by ABAQUS and Fe-Safe coupling and simulated calculation,and the test of the influence of different surface residual stress on fatigue life was carried out,and the influence of residual stress on fatigue life of shot peening was analyzed.In view of the stress relaxation phenomenon after shot peening intensification,the effects of different cycle times and load intensity on the change of shot peening stress field were experimentally studied.