Geometry-Driven Distortion Mechanisms in Thin-Walled Rotating Shells Fabricated by Laser Beam Powder Bed Fusion

Laser beam powder bed fusion (PBF-LB) enables the fabrication of complex rotational metallic components for aerospace applications, such as engine exhaust nozzles and combustion liners, but the localized thermal cycles inherent to the process often lead to residual stress accumulation and geometry-dependent distortion, particularly in low-stiffness and open structures. This study investigates the thermo-mechanical response of three representative 316L stainless steel rotational geometries—dumbbell-shaped, cylindrical, and drum-shaped—in both closed and open configurations using a transient, fully coupled thermo-mechanical finite element model validated by high-resolution three-dimensional deformation measurements. The results reveal pronounced geometry- and size-dependent distortion mechanisms: for closed structures, the drum-shaped geometry exhibits the largest radial contraction and stress concentration due to its larger characteristic size and lower stiffness, with a maximum deformation of approximately 0.14 mm, whereas the dumbbell-shaped and cylindrical geometries show smaller and more uniform deformations of about 0.09 mm and 0.12 mm; open configurations experience substantially amplified distortion, with both the magnitude and vertical location of bulging governed by geometric stiffness and substrate constraint, and the open drum-shaped structure reaching a maximum displacement of approximately 1.6 mm. These findings clarify how geometric size and stiffness control stress relaxation and shape stability in PBF-LB-fabricated rotational components and provide transferable guidance for geometry-informed design and distortion mitigation in high-precision additive manufacturing.