摘要：The developing trend of the light-weight car is the using of new light-weight materials and the optimization of the car body structure. The beam construction is the major bearing part of the car body. The thin–walled beam of the light-material plays a significant role in lightening the car' own weight, saving the materials, reducing fuel consumption and air pollution. Firstly, the relationship between the thin-walled beam that is fixed in both points and the attribute of the material can be infered from the stiffness coefficient which used as the quantitative index to estimate materials. Then take the body-in-white produced by domestic car factory as an object of study, and use Cu or Al or Mg as the materials of the thin-walled beam to calculate the bending rigidity and torsional stiffness of thewhole car body by using the FEM simulation conducted in HyperMesh.The results show that under the condition of bending and torsion, the SME value is lower when the lighten materials such as Al or Cu are used as the bodywork of the thin-walled beam than steel is. Lighten material can greatly reduce the weight of the vehicle. But it also decreased the bending and torsional stiffness of the bodywork. Therefore, in order to avoid decreasing mechanical properties which caused by adopting lighten materials, we must consider the structural design of the thin-walled beam when adopt material for lightweight.
