| Auto body takes a large proportion of quality in the entire vehicle, so it is remarkable to achieve lightweight effect by designing light auto body. Especially for pure electric vehicle body (PEV), light vehicle body can make up for the low endurance mileage and power shortage.At present, there are two approaches to design light auto body. The first is to optimize body structures. The second is to adopt high-strength or low-density materials. Based on the two measures mentioned above, this paper researched light auto body structures. Considering the small quantities of electric vehicles, which causes the high cost of auto body development, this paper set up frame-type EV body structure with the method of combining material substitution with structure optimization, this paper put forward the concept of steel-plastic integrated structure. This research content as follows:The research significance of light auto body was discussed first in the introduction, in which the importance of light auto body of EV was specialized. The relevant circumstances in traditional vehicles and PEV was described. And the current research as well as technical approach of light auto body were discussed in this part.The main methods and theory used in this subject were discussed in detail in the second chapter. Such as structural optimization and modal analysis. In the current optimization design of body structure, topology optimization of the conceptual design phase, morphology optimization of the basic design phase and size optimization of the detailed design phase were used to guide the structural design. By modal analysis, especially numerical modal analysis, structural dynamic problem can be take into account in the conceptual stage to ensure the dynamic performance of the whole structure.In order to get reference design index of frame structure and Steel-plastic integrated structure, the finite element analysis of a micro-car body structure was made. the finite element model of micro-car body structure was established, and the static bending stiffness, torsion stiffness and free modal analysis were made. The analysis of basic performance verifies that the basic performance of this micro car meets the design requirements. Meanwhile, stiffness index and dynamic characteristic design indexes of the new frame-type structure and steel-plastic integrated structure Lightweight design were obtained.In view of the characteristics of EV, such as small-lot, high development and manufacture cost, low endurance mileage as well as power shortage. The frame-type EV body structure was put forward in this paper. Based on the analysis of the performance of the micro-car body structure, frame-type EV auto body was designed though the methods of finite element analysis, topology optimization and dimension optimization, which could meet EV requirements. At the same time, in order to design lightweight electric vehicle body by changing material, this paper presented steel-plastic integrated body structure. Based on traditional sheet metal structure of auto body, a certain thickness of reinforced plastic was coated on the sheet metal through specific plastic injection molding process, so as to reduce the thickness of sheet metal and improve the performance of structures by using low density materials. Before designing steel-plastic integrated structure, the feasibility of the structure performance was verified by sample parts, then the steel-plastic integrated body structure was designed. The designed steel-plastic integrated body structure was superior to the traditional sheet metal body structure, which was validated though the usage of sensitivity analysis and dimension optimization. This research presents a new idea to use plastic in the auto body's lightweight design. |
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