Manufacturable topology optimization for thin-walled cross-sectional design

Thin-walled cross-sections are widely used in lightweight engineering structures because of their excellent stiffness-to-weight and torsional resistance characteristics. However, topology optimization of thin-walled cross-sections remains challenging because conventional density-based methods often suffer from blurred boundaries, excessive design variables, and difficulties in generating directly manufacturable configurations. To address these limitations, this paper proposes a manufacturable topology optimization method for thin-walled cross-sections using moving morphable bars. The structural topology is represented explicitly by parameterized bars, while a hyperbolic tangent aggregation scheme is introduced to construct a crisp density field with clear structural boundaries. The bending and torsional moments of inertia are evaluated within a unified finite-element framework, where the torsional rigidity is calculated through the Prandtl stress function formulation. Analytical sensitivities with respect to geometrical design variables are derived to enable the direct gradient-based optimization using the method of moving asymptotes. In addition, an adaptive move-limit strategy is developed to improve convergence stability and manufacturability. Numerical examples involving pure torsion, pure bending, and combined loading conditions demonstrate that the proposed method can efficiently generate lightweight and fabrication-ready thin-walled cross-sectional configurations while satisfying prescribed mechanical performance constraints.