Structural assessment of optimised stainless steel wavy square hollow sections for additive manufacturing

Square hollow section (SHS) is now widely used in the civil engineering industry due to its superior mechanical behaviour. However, SHS with large width-to-thickness ratios is highly susceptible to local buckling. Therefore, to enhance their resistance, this paper presents a comprehensive study on the shape optimisation and assessment of compressed selective laser melting (SLM) 15–5PH stainless steel wavy square hollow section (WSHS), which is now feasible via additive manufacturing (AM) technique. SLM is one of the important metal AM technologies due to its advantages of free-form fabrication, short process cycles and high forming precision over traditional manufacturing and thus adopted in the current paper. The adopted optimisation framework employs the particle swarm optimisation (PSO) algorithm, integrating computer-aided geometric design based on Matlab and Rhino 3D, as well as nonlinear numerical simulations through Python and Abaqus. The structural responses of the optimised WSHS specimens with varying basic optimisation parameters and geometric parameters (i.e. member length and width-to-thickness ratio), are analysed and compared to that of reference SHS specimens. A typical optimised WSHS-100 × 100 × 1–80-5 specimen shows that its ultimate stress is 3.21 times greater than that of the reference SHS specimen. Overall, greater benefits are observed in shorter specimens and relatively slender sections, as evidenced by the optimisation results. This optimisation work demonstrates the industrial potential of AM to enable resource-efficient, lightweight structural designs with geometric freedom for applications in aerospace and architecture.