Abstract: This paper studies the lightweight design method of the twist beam of rear suspension of a domestic passenger car. The whole vehicle's rigid-flexible coupling model with flexible twist beam was built using multi-body dynamics software. Modal test of the twist beam in a free-free configuration and vehicle road test of ride comfort were carried out to verify the validity of the proposed model. On this basis, the modal displacement time history of the twist beam was calculated from a dynamic simulation on the durability enhancement road. Then the stress time history of the twist beam was obtained based on Modal Stress Recovery (MSR). According to the nominal stress method, fatigue life of the twist beam was assessed. Furthermore, mesh morphing technology was employed to build the parametric model of the twist beam, which was used to define the design variables. Then, the Kriging approximation model and particle swarm algorithm were adopted to perform the multi-objective optimization of the twist beam. The mass and fatigue life were defined as the objective functions, while the first modal frequency and torsional stiffness were taken as the constraints. The Pareto optimal set was found and one of the optimal solutions was chosen to check the effectiveness of the optimization method. The results indicate that the weight of the optimized twist beam is reduced 20.35% while its fatigue life satisfies the design requirement.

Key words: vehicle engineering, lightweight design, modal stress recovery, fatigue life, mesh morphing, particle swarm optimization