Structure Analysis And Optimization Design Of The Frame Of EV

According to power source, vehicle can be divided into internal-combustion engine (ICE) and electric vehicle (EV), EV also can be divided into three classes, pure electric vehicle, hybrid electric vehicle, fuel cell vehicle. The biggest distinction between ICE and EV is that they have different powertrains, which is setting on the frame, therefore, in the process of designing frame there are different ideas between powertrains. The design of electric vehicle is different from ICE vehicle, so we couldn't depend on experience entirely Along with the development of electric vehicle, our country has made great efforts to import and research electric vehicle. Such as FAW has imported a hybrid electric vehicle which named PRIUS from TOYOTA, DFM has designed a hybrid bus by themselves, and SAIC Group, BYD, WanXiang Group have inputted a large money to design a electric vehicle of their own, they wanted to be a constituent part of the vehicle industry in environmental protection in the future. So many competitors thought electric vehicle would have a good future, so who mastered the advanced design methods, who would win in future.This paper has studied sorts of finite element methods (FEM) and their applications in vehicle design. It also introduced the theory of topological optimization method and the related software that used in vehicle industry in detail. And we summarized the achievement of the former people, studied how to analyze electric vehicle frame by using finite element methods, in addition to we studied how to optimize the frame by using topological optimization software. Frame is one of the important parts in the vehicle. According to the characteristic of the frame side rail, frame can be divided into four forms. It supports the force come from suspension, engine, gear-box and other transmission system parts, so the strength and stiffness of the frame decides the strength and stiffness of the vehicle. In the process of vehicle design, using advanced method to design and analysis vehicles could reduce human work and ensure the quality of design, and these were important for vehicle design.In this century, FEM is an advanced method, its main theory is to discrete continuous bodied structure. That is to mesh infinite continuous structure to finite elements which would have good convergent solutions. By using this method, we could calculate the stress, strain, stiffness and vibration frequencies value which we were focus on, and we also could execute intelligent optimization on the structure. Structure topology optimization is one of the intelligent optimization methods, compared with dimension optimization and shape optimization it has more design degrees of freedom and wider design space. It was regarded as more complicated and most challenging subject in optimization area. In the development of topological optimization method, variable thickness algorithm, homogenization method, variable density algorithm and moving asymptotes algorithm etc. was proposed, they are all valuable for some problem. But variable density algorithm is one of the widest used algorithm, and we had used this method and related software optimizing the frame structure of an electric vehicle. First, we analyzed the structure of the frame with linear static analysis method, according to the result like stress and displacement value, we could find that the side rails were low strength and low stiffness at the middle of the frame. This result matched the result of the test and trial-manufacture of this frame. And then we proposed an optimization object to the frame. By using topological optimization software to optimize the frame we could find a useful density distributing map. Finally, based on this map we redesigned a concept frame structure. After analyzed the new frame structure by using FEM, we compared the strength and stiffness with the original frame, they all improved.