People's high requirements for car ride comfort and collision safety promote the development of traditional fuel vehicles to become stronger and heavier, resulting in more energy consumption and exhaust emissions [1], which violates the requirements of energy conservation and emission reduction. The lightweight design of automobile body is not only an effective measure to extend the driving range, but also can improve the handling stability and ride comfort of the whole vehicle.
Lightweight means mainly include lightweight structural design and the application of new materials and new technologies. Among them, the application of new materials is the most direct and efficient means. The density of aluminum alloy is 1/3 of that of steel, its energy absorption performance is 2 times that of steel, and it is relatively corrosion resistant [2]. When aluminum alloy is selected to make body structural parts such as the rear longitudinal beam of the body instead of its traditional steel structure, it can not only reduce the body quality, but also ensure the stiffness of the body node, meet the collision avoidance requirements, and improve the collision safety of the whole vehicle.
The rear longitudinal beam of the car body is the main load-bearing and energy-absorbing part of the car in the event of the rear collision. The traditional steel body is generally formed by the stamping of high-strength steel plate, but the serious deformation of the longitudinal beam in the rear collision condition will lead to the damage of the fuel tank and fuel leakage. For electric vehicles, the battery pack will be squeezed and deformed, and the battery pack will be damaged. Wang Li et al. [3] added reinforcing plates to the weak area of the rear longitudinal beam, added weakening ribs to the tail of the longitudinal beam, used stronger mounting brackets and adjusted solder joints to optimize the rear longitudinal beam assembly and improve its impact energy absorption characteristics. Yang Jikuang et al. [4] used the orthogonal experimental design method and the comprehensive balance method to optimize the plate thickness and material parameters of the rear longitudinal beam and rear bumper. Sun Xilong et al. [5] optimized the rear longitudinal beam by extending the length of the rear longitudinal beam, increasing the number of guide slots and solder joints, and improved the rear collision performance. Although the above method has a certain improvement in the rear impact performance, it increases the vehicle mass and is not conducive to the lightweight of the body. Xu Xin et al. [6] and Yang Zhiqiang et al. [7] applied the laser-welded plate structure to the rear longitudinal beam, which has better collision resistance and obvious lightweight effect compared with the spot-welded lap structure scheme. Kim et al. [8] analyzed the energy absorption degree and failure mechanism of longitudinal beams under different loads through parametric modeling. Vacuum high pressure casting aluminum alloy rear longitudinal beam has a large design space and design freedom, and can be used to improve its impact performance and lightweight effect. In addition, the high-pressure casting integrated forming technology replaces the traditional multi-steel welding structure, integrates multiple installation points in one body, and realizes modularity, which is conducive to the improvement of body stiffness.
In this paper, the light weight design of vacuum high-pressure casting aluminum alloy rear longitudinal beam of an electric vehicle is described from four aspects: material selection, structure design, process design and product performance analysis.
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