Section property method and section shape method for the optimum design of vehicle body structures

Recently, automotive manufactures are concentrating their interests upon lightweight vehicles. Improvement of the body structure has become a big issue for effective fuel cost down and reducing the environmental pollution by exhaust gas. On the other hand, accompanying the increase of the required performance such as the improvement of safety and the reduction of vibration and noise, the weight of vehicles tends to increase. In order to solve the problem, attention has been paid to the design technique for the optimization of structures, in which a computer derives the optimal solution based on conditions defined by designers. Especially, the results of the research and the applications to the vehicle body structure have been reported in great numbers of papers. In this study, two methods for the optimization of vehicle body structure are proposed for practical application. One is the 'section property method' which uses section properties as design variables. This method shows the tendency of an optimum section approximately. The other method is the 'section shape method' which utilizes geometric parameters of section as design variables. Practical solutions are obtained by this method. These two methods are compared through several sample problems. The finite element method is used for the structural and sensitivity analyses.