Abstract: In order to explore the design method of lightweight aluminum-alloy vehicle body, the finite element analysis method and the overall evaluation method of aluminum-alloy body structure are emphatically discussed with an aluminum underbody as an example in this paper. Firstly, the shell element is used to simulate the welds of aluminum-alloy, a finite element model for vehicle body is built, and a simulation on its basic performance is conducted with a result showing that compared with the results of bending / torsional stiffness tests and modal test, the relative error of bending stiffness, torsional stiffness, 1st-order bending mode and 1st-order torsional mode are -2.45%, -3.59%, -3.43% and -2.73% respectively, verifying the correctness of the FE model for aluminum-alloy vehicle body. Then a concept of generalized structure stiffness is introduced for evaluating the force transfer performance of vehicle body, and by identifying the force transfer path of vehicle body the weak regions of vehicle body structure are located and a structural modification is performed. After optimization, the bending stiffness, torsional stiffness, 1st-order bending mode and 1st-order torsional mode of vehicle body increase by 5.59%, 1.99%, 2.42% and 0.65% respectively, while the body mass has a slight rise (0.19kg), demonstrating the effectiveness of the overall structure assessment method of vehicle body based on generalized structure stiffness.

Key words: aluminum vehicle body, finite element analysis, generalized structure stiffness, structure assessment method, lightweighting