Mesh sensitivity assessment of shot peening finite element simulation aimed at surface grain refinement

hot peening process is widely used as a surface treatment for metallic components to generate surface compressive residual stresses, work harden the surface layer of material and consequently improve the component's fatigue behavior. Numerical simulation is much helpful to limit the costly and time consuming experiments. Thus several approaches have been suggested for numerical simulation of shot peening in the recent years. However no comprehensive assessment has been yet done to perform parametric study of the process and its favorable effects. This study has focused on numerical simulation of severe shot peening, generally aimed at creating a fine grained layer of material on surface of the treated part. Mesh size effects have been particularly studied and analyzed, not only on residual stress computation, which has been always dealt with, but also by considering the accumulated equivalent plastic strain (PEEQ). PEEQ is recognized as a key parameter in the development of grain refinement process. In the end, a practical method is suggested to estimate the value of PEEQ independent from element size to be employed for assessing the generation of refined grains.