Numerical studies on the influence of thickness on the residual stress development during shot peening

Abstract

Shot peening is an important and in industrial production widely-used mechanical surface treatment with the purpose to improve fatigue life of components subjected to cyclic loading by inducing compressive residual stresses in the surface near region of the treated component. Finite Element simulation models are being developed since more than three decades in order to investigate, understand, explain, and predict the correlation between the influencing factors of shot peening and the post process residual stress state. All of the FE models proposed in literature have in common that the component thickness can not be taken into account realistically as an influencing parameter. To overcome this shortcoming a more sophisticated type of boundary condition was developed and investigated. With this boundary condition effects of thickness on the residual stress state were studied and the differences to the boundary conditions known from literature were analyzed. Obtained simulation results were compared with experimental x-ray stress measurements. The strain rate dependent deformation behavior of the investigated and aged material IN718 was taken into account using an elasto-viscoplastic material model with combined isotropic and kinematic hardening. An important finding was that a small thickness has no influence on the compressive residual stresses in the surface region but great influence on the tensile residual stresses present in deeper regions.