Surface impact analysis in shot peening process

The quality of the ultrasonic shot peening treatment, which consists of projecting spherical beads onto a workpiece using a sonotrode vibrating at 20 kHz, is strongly dependent on the impact features. This motion of the beads obviously depends on their quantity, the excitation source, and the materials comprising the chamber. The average depth of impact marks on a copper tube, shot peened in different configurations, was measured by confocal microscopy. The impact depths differed along the circumference of the tube and depended upon whether the chamber was lined with steel or a polymeric material. Finite element simulations of normal impact give a linear relationship between plastic depth and incident velocity. In addition, simulations of the whole shot peening process were performed using a discrete element method to access the velocity of the shot-piece impacts. Our results show that the average impact velocities obtained numerically are strongly correlated with average impact depths, thereby validating the numerical simulation for this shot peening configuration.