Research On Stiffness And Modal Performance Of SUV Car Body Structure Based On NASTRAN Analysis

With the continuous development of society, people increasingly essential for motor vehicles, consumer demands for cars are gradually diversifying. That is, people are not only satisfied with the automotive functions, which might require cars to be improved on construction and performance, while the body is one of the largest systems affect the vehicle performance. SUV in modern cities almost all use the bearing body, and this kind of body endues the load from general assemblies of automotive, such as the powertrain system, suspension system and exhaust system, which puts higher requirements forward the static and dynamic mechanical properties such as stiffness and modal. CAE technology as the representative of finite element analysis technology, plays a quite important role in the modern design of body. FEA is almost throughout the whole process of automotive design, it can not only greatly decrease the development cycle of new models, but also reduce costs.The research in this paper came from a development project of a SUV performance.Based on the static analysis, modal analysis, sensitivity analysis of body structure and the CAE simulation technology. BIW was analyzed, and the simulation results were compared with the experimental values to ensure the accuracy of simulation. The aim of this study is to make body to meet the requirements of bending rigidity, torsion rigidity,intrinsic mode and dynamic stiffness of the mounting points, and also improve static and dynamic nature; establish the relationship between part thickness and stiffness and the sensibility of modes; reduce weight by optimizing the size of single objective without reducing the stiffness and modal. The main contents are as follows:Introduced the modeling process of FE model as well as the material parameters, then simplified the details of the body, and finally the whole body was meshed by using shell and tetrahedron element in order to establish the detailed model for FEM analysis.Analyzed and evaluated the body modal, rigidity (bending rigidity and torsion rigidity)and the dynamic stiffness of the mounting points, and compared the results of the simulation with the experiment data. Then, improve partial structure and joints design to control modal and dynamic stiffness of the origin if some modes and dynamic stiffness of the mounting points fail to meet the requirements. Reasonably strengthened weak links of body to improve its stiffness and modal.Carried on sensitivity analysis to bending and torsion stiffness and 1st torsional modes to find out plates with higher sensitivity, then optimized the single target size by using software OptiStruct, and the mass of body reduced 4.3kg after optimization. which could both lighten the weight of body-in-white and guarantee its stiffness and modal.