Distortion in LPBF Cantilevers Governed by Stiffness-Controlled Stress Redistribution

Residual stresses generated during laser powder bed fusion (LPBF) can cause substantial distortion in slender structures, compromising dimensional accuracy and structural reliability. This study tests the hypothesis that, under identical nominal processing conditions, geometry-dependent stiffness and constraint govern how the evolving thermally induced stress field is redistributed and manifested as warpage after support removal. Bridge-type TA15 titanium alloy cantilever specimens with different spans, thicknesses, and support densities were fabricated by LPBF, and their post-cut warpage was quantified by three-dimensional scanning. A coupled thermo-mechanical finite element model was validated against the measured deformation profiles and subsequently used to examine simulated stress evolution during deposition and redistribution after support removal. Cantilevers with different spans approached similarly high simulated surface tensile-stress plateaus in the constrained as-built state but exhibited markedly different measured warpage after cutting, showing that the as-built stress magnitude alone does not reliably rank post-release deformation. Increasing span reduced global flexural resistance and enlarged the effective bending arm, whereas increasing thickness enhanced flexural rigidity and suppressed curvature even when relatively high localized stress was retained. With the total support volume held constant, changing support density altered the system-level constraint through the combined effects of support-leg stiffness, support spacing, local thermal and mechanical response, and deformation compatibility. Together, these results provide an experimentally supported process-structure interpretation of LPBF cantilever distortion across controlled variations in span, thickness, and support distribution.