3D Finite Element Models of Shot Peening Processes

Abstract

The principle of shot peening is to hit the surface of a metallic part with spherical shots to introduce a compressive residual stress field by plastification. The compressive stress introduced by shot peening lowers the number of cracks initiation on the material's surface. This process is thus used to increase fatigue life of many mechanical parts. The efficiency of shot peening depends on parameters such as the coverage rate or the size and speed of the shots. The values chosen for these parameters should be accurate to obtain the required fatigue life; investigations on the influence of the shot peening parameters, should be efficient and easy. A few analytical models have been proposed to better evaluate the residual stress field of a shot peened part, but most of the knowledge on shot peening processes today is empirical. In this study we chose to use a finite element model. Indeed, finite element codes are now powerful enough to simulate shot-peening processes extensively and to analyze the influence of the relevant parameters. This paper presents finite element simulations of shot peening processes and the residual stress fields obtained. We validated the model with a confrontation between numerical and experimental results. Two types of materials often used in aircraft and automobile industry were chosen for the study. The mechanical properties of these two materials were experimentally measured. In the same way, the coverage rate, the diameter and the speed of shots used to treat the surface of the materials were evaluated. Selected data were extracted from the literature and experimental measurements carried out in our laboratory. Three-dimensional models reproducing the experimental conditions were then investigated to simulate the shot peening of these materials. Results such as the displacement and the residual stress field are presented and compared to experimental results when possible. The models proposed show how the finite element simulation is able to predict the residual stress field of a shot peened part. The possibility to vary parameters values easily confirms the interest of shot peening numerical simulations.