Fatigue Life Prediction of Laser Shock Peened LPBF Steel Considering Surface Defects and Residual Stress Relaxation

Laser shock peening (LSP) is an advanced surface strengthening technique that improves the fatigue resistance of laser powder bed fusion (LPBF) metallic components by introducing compressive residual stress and modifying surface microstructure. However, accurate fatigue life prediction remains challenging due to the influence of defects and residual stress relaxation. In this study, a fatigue life prediction model is developed by considering residual stress evolution and defect‐induced stress concentration. The model integrates residual stress prediction derived from LSP parameters with an analytical formulation based on local stress–strain theory to describe stress redistribution. Defect‐induced stress concentration is incorporated and characterized by surface valley depth and curvature. The results indicate that although higher LSP energy increases local stress concentration due to sharper surface valleys, the enhanced and more stable compressive residual stress dominates fatigue performance. The model provides a predictive tool for fatigue design and LSP strengthening strategies of additive manufacturing components.