Angle-Dependent Inherent Strain in LPBF Overhang Structures: Modeling and Residual Stress Validation

Low-angle overhang structures in laser powder bed fusion (LPBF) experience strongly geometry-dependent thermal conditions because the underlying material progressively changes from consolidated solid to low-conductivity powder, which raises a fundamental question regarding the conventional use of a uniform inherent strain for efficient residual stress and distortion prediction. In this study, the dynamic inherent strain (DIS) method is employed to investigate the inherent strain behavior of LPBF overhang structures with different tilt-angles. The results reveal that after excluding the boundary-affected stages of the build, the representative inherent strain exhibits a systematic dependence on tilt-angle in both magnitude and tensor characteristics. Based on this angle dependence, compact angle-dependent expressions are established using trigonometric basis functions for engineering implementation. Comparisons with residual stress measurements at the experimentally investigated 30° and 90° geometries further indicate that angle-specific inherent strain assignment has a greater influence on the mechanical response toward the lower bound of the investigated angular range.