Shot velocity measurement using particle image velocimetry and a numerical analysis of the residual stress in fine particle shot peening

Fine particle shot peening has the advantages of producing compressive residual stress, microscale work hardening near the surface, and minimal surface roughness. Therefore, fine particle shot peening has been applied to numerous parts to improve fatigue strength. In this study, the shot velocity of fine zircon and stainless steel shots at four values of air pressures were precisely measured using particle image velocimetry. The shots were accelerated to a standoff distance of approximately 80 mm from the nozzle outlet. The shot velocity of the zircon shots is faster than that of the stainless steel shots. The measured shot velocity for both shots is almost proportional to the 0.5th power of the air pressure. To investigate the effect of the measured shot velocity on the residual stress distribution in an aluminum alloy (A5052) plate, a finite element model was developed for fine particle shot peening. The analyzed residual stress distributions using the accurately measured shot velocity agreed well with those measured in four test pieces using the zircon and stainless steel shots at two air pressures. The shot velocity measurement method and numerical analysis model for residual stress were both validated.