Effect of Shot Peening Process Optimization on Fatigue Performance of 5083 Aluminum Alloy Welded Joint

A random multi-projectile motion model was established with Abaqus software. The residual stress distribution of 5083 aluminum alloy butt joints after shot peening was simulated, and the effect of bullet diameter (0.3, 0.4, 0.5 mm), shot peening speed (20, 30, 40, 50 m · s⁻¹) and coverage rate (100%, 200%, 300%) on residual stress was analyzed. The relative good shot peening parameters were initially selected. Under relatively good parameters, the shot peening intensity was increased from 0.150 mm to 0.175,0.200 mm while keeping the bullet diameter and coverage rate unchange, the effect of shot peening intensity on the surface quality, residual stress, hardness and fatigue performance of the joints was further studied through tests. The optimal shot peening process was determined. The results show that the relative error of the simulated residual compressive stress and the residual compressive stress affecting layer depth was approximately 4.7%, 10.5%,respectively, indicating the model was accurate in predicting the residual stress. With the increase of bullet diameter, the surface residual compressive stress and the maximum residual compressive stress decreased, and the residual stress affected layer depth and surface roughness increased. With the increase of shot peening speed, the surface residual compressive stress, the maximum residual compressive stress and the residual stress affected layer depth first increased and then tended to stabilize, and the surface roughness increased. With the increase of coverage rate, the surface residual compressive stress and the surface roughness increased, and the maximum residual compressive stress and the residual stress affected layer depth showed no significant change. Considering the indicators of large residual compressive stress and small surface roughness, the initially selected better shot peening process was determined as bullet diameter of 0.3 mm, coverage rate of 200% and shot peening speed of 40 m · s⁻¹. With the increase of shot peening intensity, the surface roughness increased, the residual compressive stress and the surface hardness increased, the maximum residual compressive stress first increased and then decreased, the depth of the residual stress affecting layer and the hardened layer were both around 240 μm, and the fatigue life first increased and then decreased. The optimal shot peening process parameters were as follows: bullet diameter of 0.3 mm, coverage rate of 200% and shot peening intensity of 0.175 mm (shot peening speed of 44 m · s⁻¹). Under this condition, the residual compressive stress of the joint was large, the surface roughness was moderate and the fatigue performance was the best.