Topology optimization of the bracket used between the profile and seat frame in buses

This thesis focuses on the structural optimization, weight reduction, and cost efficiency of seat brackets used in buses, particularly those positioned between the seat frame and chassis profile. In passenger transportation vehicles such as city and intercity buses, ensuring passenger safety while minimizing production cost and structural weight is a critical design objective. The aim of this research is to develop optimized bracket geometries that can withstand applied loads while minimizing excess material use. A total of six different bracket configurations were generated through topology optimization, each designed with unique geometrical features and load transfer paths. For each design, six different steel materials — DP800, DP600, AISI 304, AISI 316, ST52, and ST37 — were assigned to create a comparative dataset. Static structural simulations were performed using the finite element analysis software Abaqus/CAE. The loading conditions were defined in accordance with the ECE R80 regulation, which governs safety standards for seating systems in public transport vehicles. Each bracket-material combination was analyzed to determine the maximum von Mises stress, total displacement, and safety factor values. The structural integrity results were further supported by an economic evaluation that included the July 2025 market prices of each material and additional surface coating costs for non-stainless materials via cathodic electrophoretic deposition (KTL). The study results demonstrated that brackets produced using DP800 steel exhibited the best overall performance, providing a high strength-to-weight ratio and cost advantage. While AISI 304 and 316 stainless steels offered excellent corrosion resistance and structural reliability, they were found to be economically unfavorable. Conversely, ST52 and ST37 provided lower costs but failed to meet the required safety margins in most configurations. DP600 offered intermediate results but fell short of DP800's performance. Therefore, the optimal combination of mechanical durability and cost-effectiveness was found in the topology-optimized DP800 brackets. These findings offer valuable insights into material selection and lightweight design strategies for future commercial vehicle applications where safety, cost, and efficiency must be simultaneously optimized.