A design for lumped mass of a shot model in random peening simulation and prediction of dimple size evolution

Finite element (FE) simulations are commonly used to investigate shot peening effects by implementing the impact process of multiple shots upon a target which with small geometry size. The target is selected with small size from the practical large component to economize the computational resources in simulation. Under this condition, the lumped mass of each shot in FE simulation should be designed according to its impact position on the target to balance the influence of boundary constraints. Aiming to obtain the same indenting depth of a shot impacting at any position, the evolutions of indenting depth and related energies are studied. An approach is proposed based on the strains and stresses of an impact on semi-infinite body to design the lumped mass of shot on various shape targets. With the proposed approach, a random peening process involving 300 impacts is simulated to detect the size evolution of dimples, which is useful for determining peening coverage precisely. The random peening simulation presents a decrease of average dimple size with impact density. And regular multiple-impact simulations present the same trend, indicating the capability of multiple-impact analyses on the prediction of dimple size evolution. The simulation results are verified by shot peening experiments.