Thermo-mechanical mechanisms governing stress and deformation in lightweight hollow structures fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is increasingly adopted for manufacturing lightweight aerospace components with complex internal geometries; however, the thermo-mechanical response of hollow structures is highly sensitive to geometric discontinuities, often resulting in severe residual stress accumulation, warpage, and cracking that compromise dimensional accuracy and structural integrity. In this work, the thermo-mechanical behavior of LPBF-fabricated lightweight hollow structures is systematically investigated through combined experiments and simulations. Four representative hollow geometries with identical overall volume are designed by extracting structural features from lightweight aerospace components with hollow characteristics, while the hollow shape and number are deliberately varied. The specimens are then fabricated, followed by partial constraint removal to activate residual stress relaxation, and the resulting deformations are quantified by 3D scanning. A coupled thermo-mechanical finite element model is calibrated against experimental measurements and employed to analyze stress evolution and deformation throughout the LPBF process. The results demonstrate that hollow-shape-induced variations in the number of deposited layers above the hollow dominate residual stress accumulation and final warpage, establishing a layer-number-dominated deformation mechanism. Although increasing the number of hollows elevates the overall residual stress level, deformation is effectively suppressed due to enhanced structural stiffness and constrained stress-release pathways. Furthermore, systematic variation of the top deposited section reveals that reducing the deposition area (XY plane) significantly mitigates stress accumulation, highlighting an area-dominated stress-regulation effect. These findings provide physics-based insight and practical design guidance for optimizing lightweight hollow structures with improved dimensional stability in LPBF.