Research On Elimination Of Turning-induced Residual Stress For Pure Copper By Heat Treatment

In the machining process of large weakly rigid components,the residual stress introduced by cutting is an important factor leading to machining deformation.The heat treatment can effectively reduce the residual stress in the cutting surface,but it cannot completely eliminate the residual stress in the limited heat treatment time.Therefore,the determination of residual stress after heat treatment has important guiding significance for the prediction and control of subsequent machining deformation.In this paper,the influence of the evolution of surface grain size and dislocation density of pure copper on the release of turning-induced residual stress during heat treatment was considered.The accuracy of the model was verified by experiments,and the distribution of residual stress and workpiece deformation after heat treatment were obtained.The detailed research contents are as follows:(1)In this paper,T2 pure copper was taken as the research object to carry out pure copper cutting experiment and heat treatment experiment.The residual stress distribution of turning subsurface before and after heat treatment was measured by the blind hole method based on electronic speckle interference,and the experimental measurement of grain size and hardness of subsurface under different heat treatment parameters was carried out.The effects of different heat treatment temperatures and holding time on the grain size and dislocation density distribution of subsurface of pure copper after cutting and heat treatment were obtained..(2)In order to describe the process of residual stress on the surface of turning pure copper during heat treatment,a residual stress release model based on creep model was established.The effects of initial hardening state caused by turning,evolution of grain size and dislocation density on residual stress during heat treatment were considered.Different hardening states were prefabricated by rolling and stress relaxation experiments were carried out to calibrate the parameters in the residual stress release model of pure copper.(3)Based on the finite element software ABAQUS and VUMAT subroutine,a turning simulation model considering microstructure evolution was established to obtain the subsurface grain size,dislocation density and residual stress after turning.The turning simulation model was verified by residual stress measurement experiments.Simulation model to establish 3 d global pure copper workpiece heat treatment,turning residual stress mapping by stress mapping method to the 3 d residual stress field in the global,consider turning the surface grain size and dislocation density,based on pure copper residual stress release model,predict turning pure copper after heat treatment on the surface of the workpiece and the residual stress and deformation of workpiece,The simulation model of heat treatment was verified by experimental residual stress measurement and deformation measurement.