A novel skeleton structure using topology optimization design for automobile rear subframe

Automobile subframe is key chassis component that connect the suspension to the car body, requiring high stiffness, strength, and vibration resistance under lightweight constraints. This study proposes a novel skeleton-type rear subframe design framework inspired by natural skeletal structures, incorporating multi-stage optimization strategy to balance structural performance and weight reduction. First, to obtain boundary conditions for optimization, a rigid–flexible coupled multi-body dynamic model of the rear suspension is established to obtain the loads acting at the key connection points under different load conditions. An efficient multi-load condition topology optimization model is then employed to minimize the subframe’s mass, bridging the gap between the initial design and target weight. Optimization control parameters are systematically analyzed and selected to ensure convergence toward an ideal topology. Subsequently, a multi-objective topology optimization (MOTO) approach is implemented to simultaneously minimize compliance and maximize the first-order natural frequency, with weighting coefficients for different load conditions determined objectively using gray relational analysis (GRA). The optimized steel subframe has a mass of 22.5 kg and the first-order modal frequency of 232.7 Hz, meeting both the lightweighting and requirement and multi-performance requirements. The proposed method provides an effective framework for designing lightweight, high-performance, and cost-efficient automotive subframes.