The Study On Structural Lightweight Design Method Of Bus Frame

Lightweight design is an important way to improve car's performance. With satisfying the prerequisites of body strength and safety, decreasing the weight of a vehicle will largely improve its dynamics, handling, braking performances and fuel economy. Related research shows, a 10% decrease of the car weight will improve the efficiency of the fuel by 6-8%,which is beneficial to less fuel consumption and air pollution. Lightweight design is necessary for fulfilling the“Energy Conservation and Emission Reduction”objective in our country, and it is also necessary for enhancing the competitiveness of the automobile manufacturing companies.Finite element method is an effective numerical computational method. The structure displacement field computed through this method can be considered as the original criteria or the foundation of the improving the structure design. It can compute the results of various designs correctly and quickly. Thus, the finite element analysis has become a key stage of vehicle design and research. It has also been wildly used in the automotive industry and become a common method for automotive design.The paper aimed at the lightweight design of long distance bus body structure, and the finite element method was employed to model the body structure. Based on the rigidity and modal analysis on the framework of bus body, the topology optimization and sensitivity analysis were performed on the body structure and framework, respectively. The results showed that the weight of body framework was decreased by 568 kg after the topology optimization design; however, the stiffness of bus framework was decreased compared to the original design. Then, 24 groups body parts(it contains 48 parameters) were selected as optimization variables to execute sensitivity analysis on bending and torsion rigidity. The optimized design largely increased the stiffness, raised the frequency of first-order modal from 6.59 Hz to 7.00 Hz, and also strengthened the isolation effect against to road excitation as well as achieving reducing weight by 22.5%. The research method in this paper can be considered as an effective way of lightweight design for long distance bus, and it will provide an effective assistance to the development process of bus body structure.