The Machined Surface Residual Stress Of High Strength Steel And Its Influence On Fatigue Life

The fatigue life of workpiece is one of the most important performance indexes while the residual stress plays a significant role as the bridge of the surface performance and machining process.This paper is an in-depth study of workpiece surface residual stress dispersion and the distribution along the depth curve and its influence on fatigue life for high-strength steel under different machining processes.The study uses quenched Cr12MoV as the material of samples.Several experiments were conducted including single-factor experiments under different cutting conditions,contrast experiments of cutter geometry parameter and grinding experiments under different velocities.The test of surface residual stress with three points and the curve test along the depth distribution by using i XRD were also conducted.Based on the dispersion calculation for residual stress with three points of statistics,the influences of different machining processes on the dispersion of residual stress were analyzed;by drawing depth direction residual stress distribution curve,the contrastive analysis trend curve under different parameters was made.Secondly,with a view to studying the effects of residual stress on the fatigue life of the sample,the sample's alternating stress of non-zero average stress was extracted by using ANSYS to simulate the sample's stress state under the rotating bending fatigue experiment;the dispersion of residual stress and the influence of pressure stress curve on fatigue life were analyzed by building the fatigue theory model.The fatigue sample under the parameter corresponding to residual stress,was used to do the rotating bending fatigue experiment,setting up a three–dimensional diagram of dispersion of residual stress,pressure stress curve and fatigue life to analyze the influence of residual stress on fatigue life comprehensively.After the experiment,fracture analysis and the exploration for the rule of influence were done.Finally,by combining theoretical model and experimental results,surface roughness,surface residual stress dispersion,the distribution curves of residual stress,fatigue characteristics,machining efficiency,machining stability and machining flexibility were contrasted fully under two different conditions of turning and grinding processes.Through the observation of the overall index,it could provide theoretical support for the options between turning and grinding processes under the actual conditions.By adopting the approach of integrating experiments,mechanical simulations with theoretical models,the longitudinal distribution of residual stress and fluctuations of transverse dispersion comprehensively under different conditions of turning and grinding was studied,and the influences on fatigue life was analyzed,which helps provide the technical support for process parameters optimization and selection of process based on best surface properties for future actual operating conditions.