Fatigue Behavior of Post‐Processed Additively Manufactured 316L Stainless Steel: Experiments and Fatigue Damage Modeling

This study experimentally and numerically investigates fatigue damage in additively manufactured 316L stainless steel produced by selective laser melting using the powder bed fusion–laser beam process. More than 100 specimens were tested under tensile and strain‐controlled fatigue loading to evaluate the effects of surface condition, hot isostatic pressing (HIP), and build orientation. Machining provides the greatest improvement in fatigue performance by removing sub‐surface defects, while HIP provides additional benefits through reduced porosity. Vertically built specimens exhibit approximately 40% longer fatigue life than diagonal and horizontal specimens because elongated grains aligned with the build direction enhance ductility and stabilize crack propagation. A unified continuum damage mechanics‐based constitutive model predicts cyclic softening and fatigue life across low‐ and high‐cycle regimes. Fatigue anisotropy is represented by an orientation‐dependent fatigue ductility coefficient, while remaining parameters are orientation‐independent. The model accurately reproduces cyclic hysteresis loops and fatigue life to failure.