Multi-objective topology and sizing optimization of bus body frame

A genetic algorithm based method for multi-objective topology and sizing optimization of bus body frame with manufacturing constraints is presented, where a flexible strategy called independent ground structures is introduced to define different ground structures for topology optimization and sizing optimization. The finite element models of an integral bus body frame were created and validated by physical experiments, including modal test and static strength test. The formulation of multi-objective optimization is established, where the objectives are to minimize the mass, maximize the torsional stiffness and maximize the first frequency of the bus body, and the constraints include strength, symmetry and consistency. The proposed method was implemented, and the roof frame of the integral bus was chosen as the design space. A set of non-dominated solutions was obtained, among which 41 new structures are strictly better than the benchmark model in all objectives. Two structures respectively with lightest weight and highest torsional stiffness of those 41 structures are shown in the paper. The weight of the former is decreased by 97.9 kg (3.43 %), while the torsional stiffness of the latter is increased by 4.89 kN•m/deg (13.14 %).