Anisotropic fatigue life prediction of laser powder bed fusion Ti6Al4V alloy based on continuous damage model

This study presents an anisotropic fatigue life prediction model for Ti6Al4V alloy fabricated by laser powder bed fusion along different build orientations, explicitly considering ratchetting–fatigue interaction within the framework of ductility exhaustion theory and continuum damage mechanics. The total damage is decomposed into fatigue damage and ratchetting-induced ductility damage. Within the framework of Lemaitre's continuum damage mechanics, combined with the cyclic stress–strain relationship and the evolution of ratchetting strain, the damage evolution equations and fatigue life prediction model are derived for specimens with different orientations by constructing an orientation tensor and a strength tensor, respectively. Finally, a relationship among the loading conditions, build orientation, and fatigue life is established. Comparison with experimental results demonstrates that the proposed model exhibits good prediction accuracy, providing a reliable theoretical support for the fatigue life assessment of additively manufactured titanium alloy components.