Numerical Simulation And Experimental Study Of Shot Peening

Shot peening technology is used to improve the fatigue strength of materials and pats,and it is one of the most effective surface engineering technologys to extend the fatigue life.For the specific gear material 20MnTiB,it is of great significance to determine the optimal shot peening parameters and to study the influence of different parameters of shot peening on fatigue life.The method of combining numerical simulation and experiment was used to study the strengthen process and the effect of shot peening in this paper.Main works as follows:In this paper,shot peening simulation model under a single shot has been established using the finite element software.The strain hardening and strain rate hardening in the process of impact was considered in the material model and the effects of different shot diameter,shot speed and shot angle on the distribution of residual stress and surface deformation was studied.The simulation results show:With the increase of the speed,max residual stress increases first and then decreases;The diameter of the shot only affects the depth of the residual stress layer;With the increase in angle,the depth of the residual stress layer and the max residual compressive stress are both increased.Random functions and loop statements of APDL language were used to develop the shot beam model that are randomly distributed.And the effects of different shot penning coverage on the distribution of residual stress and roughness were studied.The results show:Incomplete shot peening coverage can generate the residual tensile stress at the surface;Incomplete shot peening coverage affects the uniformity of the distribution of the residual stress;When the shot peening coverage reaches 200%,the distribution of residual stress and the surface roughness value tend to be saturated.The distribution of residual stress field and the value of the roughness Ra of different shot peening parameters were detected through X ray diffraction and roughness tester.The correctness of the shot peening numerical simulation was verified.Finally,the tensile fatigue tests under different shot peening parameters were carried out.The results show:With the increase of shot peening pressure,the tensile fatigue life increases first and then decreases;The specimens that have been peened can reduce the roughness after the mechanical polishing and this can significantly improve the fatigue life;The tensile fatigue life of the specimens that have been peened is more sensitive to the low stress cycling level than to the high stress cycling level;When the shot peening coverage is less than 100%,the fatigue life can be significantly decreased.