Topology Optimisation of an Automotive Suspension Bracket Using SIMP and BESO Methods: Comparative Study with Manufacturing Constraints for Additive Manufacturing

Topology optimisation has emerged as the foremost computational tool for lightweight structural design, enabling the redistribution of material within a given design space to achieve maximum structural efficiency — minimum weight for a specified stiffness, strength, or frequency target. This paper presents a comprehensive comparative study of two leading topology optimisation methods — the Solid Isotropic Material with Penalization (SIMP) method and the Bi-directional Evolutionary Structural Optimisation (BESO) method — applied to an automotive suspension bracket (upper control arm mounting, original mass 2.84 kg, EN24T alloy steel) subjected to three-axis combined loading representative of road-induced forces. The optimisation is performed in ANSYS Topological Optimisation module and a custom MATLAB BESO implementation at five volume reduction targets from 20 to 50 percent, with the objective of minimising structural compliance (maximising stiffness). Manufacturing constraints for additive manufacturing — minimum member thickness (4 mm), minimum overhang angle (45°), and full connectivity of all load paths — are enforced throughout the optimisation. Results show that at the selected 40% volume reduction target, SIMP achieves compliance of 1246 N·mm (mass 1.70 kg, safety factor 2.18) while BESO achieves 1196 N·mm (compliance 4.0% lower, safety factor 2.28) with the same mass. Both methods increase the fundamental natural frequency by 18–25% relative to the original design despite removing 40% of material, demonstrating the stiffness efficiency improvement achieved by optimal material redistribution. The BESO-optimised geometry is reinterpreted as a manufacturable design by fillet smoothing and minimum thickness enforcement, achieving 40.1% mass reduction (1.70 kg vs 2.84 kg), saving approximately ₹2,840 per bracket in material cost with EN24T steel at ₹250/kg, or ₹4,260 per bracket if fabricated by selective laser melting in 316L stainless steel.