Research On Lightweight Design Method Of Car Body Structure Based On Parameters Variation

Lightweight design of body structure is a complex issue and it will take a long time toweight optimization design cause of its multiple variables and performance. Because of thepanels of body structure are stamped, there is a little difference between the actual thicknessand the nominal value of design. What’s more, the manufacturing structure may not meet thedesign requirements and it will affect the normal use of the future by the impact ofuncertainties in the actual processing technology and the environment. In view of this, inorder to make the design of body structure more reliable, the effect of uncertainties should beconsidered in the optimal design of body structure.Size optimization is used to lightweight design of a hybrid body structure after analyzingthe various development stages of lightweight body structure technology system. The PSAU（Performance Analysis、Sensitivity Analysis、Approximation Models、Uncertainty-BasedOptimization）methods is proposed and the modular design system of PSAU method is set up.The system is used to design the lightweight car body structure based on parameters variation.The range of design fields must be reduced in the optimization design considering thedisturbance of panel thickness, elastic modulus and properties of spot weld. The approximatemodel method is introduced to uncertainty optimal design. The strategy of sequential globalapproximate model is proposed according to the shortage accuracy problem of the priorexistent approximate model. The strategy is proposed to improve the accuracy global andlocal model. And then the radial basis function neural network sequential approximate modelis constructed to meet the accuracy requirements. In order to improve the efficiency ofoptimization, the single-loop optimal strategy based on Monte Carlo is proposed according tothe low efficiency of conventional double-loop optimal strategy, and the moving constraintstep is derivated.According to the modular design system of PSAU method, the stiffness and modal finiteelement model of body structure are established. The method of improving the precision ofsimulation of car body structure has been researched with the results of body structure modalexperiment. It makes the finite element model which is used for optimization getting more close to the actual situation. Then the sensitivity analysis is set up to selected the optimalpanels. The sample database for building the approximate model is established by usingOptimal Latin hypercube design method. The stiffness and modal approximate model is builtby using Radial Basis Functions neural network with the sample database. The uncertaintyoptimal design is executed by Adaptive simulated annealing algorithm. Considering theparameters variation of the design variables, spot diameter and elastic modulus, the optimaldesign scheme is achieved without lowering the performance of static stiffness and modal,while the quality of body structure is reduced by17.94kg. And it ensures the robustness andreliability. The desired design goal is come true. The PSAU method is significant for thefuture optimal design of car body structure lightweight design based on parametersuncertainty.