Study On The Influence Of Pre-stress On The Surface Microstructure Of The Parts In Dry Grinding Process

As the last machining process,the grinding process plays a decisive role in the surface quality of the parts.Surface residual stress,surface burns,ground cracks and other surface micro-structure damages are important factors to measure the surface quality of parts,which affect the fatigue strength,tensile strength,surface hardness and wear resistance.It impacts on the service life of parts directly and may even cause serious component failure.Pre-stressed grinding process can change the residual stress of workpiece surface,and the residual stress will affect the crack formation.Therefore,it is of some engineering significance to study the influence of pre-stress on the surface microstructure damage.In this paper,the influence of pre-stress on the surface microstructure damage in dry grinding process is studied.In this paper,the mechanism of micro-structure damage on the surface of pre-stressed dry grinding is studied,and the effect of residual stress on the crack size and the effect of pre-stress on the crack nucleation are studied by the theory of dislocation reaction.The experiment chose 40Cr steel as the grinding material and selected different grinding depths and pre-stresses to research the pre-stressed dry grinding surface micro-structure damage characteristics.Drilling method was used to measure the size of surface residual stress and analysis the pre-stressed influence of the surface residual stress.This paper has scanned the grinding hardened surface morphology with the scanning electron microscope.Combining with the experimental results of the SEM images and EDS spectrum analysis,it has analyzed the surface burns injury and the grinding cracks injury from the perspective of the role of grinding force,phase organization and pre-stressed influence.The dry grinding theory model was established,and the finite element simulation of temperature field of dry grinding was carried out by using ANSYS software.The distribution of temperature field in grinding process is obtained.The thermal-mechanical coupling of the surface grinding for 40Cr steel was simulated by writing APDL program code.The influence of prestress on the surface residual stress and surface micro crack of workpiece is studied.The research shows that the stress has a better effect on the residual stress of the workpiece surface,and the residual tensile stress in the surface layer increases with the increase of the grinding depth.The effect of grinding depth on the melt coating,the oxide film and the crack is maximum,and the pre-stress can restrain the grinding temperature,which can reduce the heat damage.The pre tension stress plays a role in the surface grinding micro crack damage by changing the residual stress state.