Stiffness FEM Analysis And Optimization On Car Body

Car body is one of the key assemblies in a car. The body performance is very important part of the general performance of the car. The performance of car body is determined by the static and dynamic characteristics of its structure. The analysis of the stiffness and modal characteristics of car body is the guidance for optimization of car structure.Using FEM, and with a domestic SRV as an example, this paper does the following research work on static and dynamic characteristics and structure optimization:Using quadrilateral or triangular shell elements, a FEM model of the body shell is established. Combining the researching results and relevant experience from both domestic and abroad, the model simplification, scale controlling, grid quality controlling and treatment of weld points are discussed detailedly.The modal characteristic of the car body is analyzed, and compares the results with the experimental results to verify the accuracy of the finite element model.This paper calculates the torsion and bending stiffness of the car body and studies the deformation of main openings in the torsion and bending loading conditions; With B-joint as an example, this paper calculates its stiffness and studies the influences of the joints on body stiffness.Takes the thickness of body as the variable, the structure sensitivity is analysed and the relative sensitivity that kinds of performances act on mass is calculated to find out the dominant part which provide main contribution to the vehicle performance;The optimization design variables are determined through the sensitivity analysis, and a structure optimization is conducted with a constraints of body stiffness,the first torsion modal frequency and the first bending modal frequency . So the torsion stiffness rises while the weight of car body is realized and the two key model frequency rising to different degrees.This dissertation belongs to engineering application subject. It needs to be studied farther in the frame design and analysis. Those actions have a realistic meaning to improve design and analysis level.