XCT-based equivalent defect for assessing the effect of contour-induced defects on fatigue strength of PBF-LB components

The fatigue performance of laser powder bed fusion components is critically governed by process-induced defects, whose distribution and morphology are strongly influenced by contouring strategies. In particular, the near-surface region affected by contouring exhibits a distinct defect population in terms of defect size and density. Several studies have shown that surface removal can expose these defects at the surface. This study investigates the role of contour-induced defects in the fatigue behaviour of additively manufactured components. A contour-informed probabilistic methodology is proposed, integrating X-ray computed tomography for defect characterisation, a virtual machining procedure to simulate material removal, and a fracture mechanics framework to evaluate defect criticality through stress intensity factors. Extreme value statistics are employed to derive equivalent surface defect distributions representative of fatigue-controlling defects. The proposed workflow shows good agreement with experimental observations for Ti6Al4V and AlSi10Mg specimens, accurately capturing both fatigue life and failure locations. The approach simplifies probabilistic modelling for components and is subsequently applied successfully to a complex engine bracket.