Abstract: Concurrently considering the dynamic and static stiffness and frontal crash safety, a forward conceptual design method of car body is presented in this paper. Firstly according to class A surface and vehicle general layout, a simplified geometric model for car body is established, 19 main cross-sections of the body is determined, and the stiffness chain model of car body is built based on beam element theory and transfer matrix method. Then rectangular front longitudinal beam is designed by using collision empirical formula, the frontal crash dynamic loading of car body is simulated by equivalent static load, and the requirements of car body deformation are put forward based on equivalent static loading condition. Next, a simulation on the main cross-section parameters of each beam element of car body is conducted by using genetic algorithm, with minimizing car body mass as objective and the static stiffness, the first order mode and collision deformation of car body as constraints. Finally, a finite element simulation is performed on an approximate benchmark car, with its static stiffness and vibration modes of car body calculated and compared with that by using stiffness chain method, verifying the feasibility of the method adopted.

Key words: frontal crash, forward design, stiffness chain, equivalent static load