Measurement of shot velocity using particle image velocimetry and numerical analysis of residual stress at two shot peening conditions

Abstract

Shot peening is applied to many manufactured parts to improve the fatigue strength of metals by introducing compressive residual stress near the surface. The distribution of compressive residual stress is mainly determined by shot diameter, shot velocity, angle of incidence, and peening time which affects coverage. In this study, the shot velocity was measured using particle image velocimetry (PIV) for shots fired at two different air pressures. The finite element method was used to analyze the residual stress distribution in a high strength aluminum alloy (A7075-T6) plate during shot peening. The shot was accelerated up to a standoff distance of approximately 200 mm from the nozzle outlet. The measured maximum shot velocity increased proportionally to the air pressure to the 0.59th power. The analyzed residual stress distributions using measured shot velocity with PIV through the thickness of the specimen agreed well with the measurements under two types of peening conditions with differing air pressure and angle of incidence. The shot velocity measurement technology and the numerical model for analysis of the shot peening residual stres were both validated in this study.

Keywords

• shot peening
• particle image velocimetry
• shot velocity
• residual stress
• finite element method