Aluminum Alloy Car Body Structure Lightweight Research Based On Large Parts Of CEMU

With the problem of resource shortage becoming increasingly prominent,the design of lightweight has drawn more and more attention by designers,in which how to achieve the trade-off between the performance improving and material using is a persistent topic.After verifying the structural strength,stiffness and modal of CEMU vehicle body,this article chooses vehicle body roof as the research object.To acquire the lightest body quality,it employs single objective and multi-objective optimization to explore multiple kinds of optimization conditions,and conducts a lightweight design considering body roof with an improved approximation model based on radial basis function.The main contents of this article include:(1)Simplify the complex vehicle body reasonably and establish the finite element model of the middle vehicle body.As the basis of the finite element model,as per relevant requirements of EN 12663:2000 and some other rules,twelve kinds of main combination cases on the middle vehicle body structure of the standard EMU were calculated and reached an expected result through the analysis on body strength,stiffness and mode.(2)Choose appropriate research object.As the large parts of the body structure,chassis,side wall and roof have a greater impact on the total weight.Therefore,these parts can be chosen for the target to achieve optimization design of lightweight.In this paper,the roof is selected as the research object,which is grouped and numbered with different regions and functions.Moreover,the thickness of these material is regarded as a design variable.(3)Design optimization strategy.By the aid of Isight software,establish an optimization strategy by using mathematical approximation model to instead finite element simulation.Firstly,create sample space in the experimental design stage by the Optimal Latin hypercube design method,then obtain the sensitivity of the design variables to the response performance by graph analysis such as interaction graph.After analyzing the accuracy of the approximate model,the Kriging method is finalized to create the approximation model.Based on the approximate model,combine Multi-Island Genetic Algorithm and gradient optimization algorithm NLPQL optimization strategy to complete single objective optimization of body quality.The effect is obvious and owns high optimization efficiency.In the multi-objective optimization,optimization is carried out aimed at body quality and stiffness two variables.By checking two results through finite element simulation and compare the changes on the comprehensive performance of vehicle body,it can be observed that multi-objective optimization result is suitable for the operation of the body roof relatively considering the comprehensive performance.(4)When dealing with scattered data by the approximation model,the discrete interpolation matrix constructed by the radial basis function is usually a morbid dense matrix,which would result in the instability of the calculation result.To solve the problem,the localized radial basis function is proposed,by the relaxation factor to improve the morbidity of the radial basis function method.Besides,the effectiveness of the improved approximation model is verified by the single objective optimization of the vehicle body.The research of this article provides certain reference value for structure analysis of high speed vehicle and the optimization design of large structure,and makes certain foundation for further studies of railway vehicle’s optimization design.