Structure Optimization Design Of CRH3 Underframe Based On Lightweight Design

The high speed railway car has been the symbol of ’Chinese Speed’ and’Going out’ card.In response to the national call to save energy,it is the main idea to make material most efficient now.The first process is to lighten the weight of CRH3,then make up the loss of stiffness.The whole content is as the following:(1)At the beginning,the geometric model provided by the manufacture must be simplified according to the importance,then the finite element model is built by using HyperMesh;(2)According to EN 12663:2000 standards of regulation,the finite element model is calculated under more than 10 kinds of working conditions and verified the accuracy based on the equivalent stress and displacement under every working condition;(3)The element size is about 70 mm.In order to confirm the correctness of the model further,it is calculated by using sub-model analysis module in software ANSYS.It is just on the concentration areas and refine the girds for the sub-model.Then the original model of the calculation result is applied to the boundary of sub-models by interpolation method.Compared with the original analysis results,the stress distribution of the sub-model is consistent and similar to it,showing the accuracy and reliability of the original model;(4)According to the above result,firstly,it is to set the thickness of the chassis parameters as design variables,stiffness as constraint conditions,the weight as the objective function for lightweight design;secondly,to set chassis steel plate location parameters as design variables,the weight as constraint condition,the maximum equivalent stress and stiffness as the objective functions for shape optimization design.It needs to get sample points and the contribution of all parameters through the analysis result during two optimization processes.Next,approximate model is established and analyzed that whether analysis error is acceptable.If adopted,choosing adaptive simulated annealing algorithm and the NSGA-Ⅱ to complete optimization processes;(5)Putting the optimized calculation results into the original model to judge whether it satisfies the requirements.Compared the simulation results with the results of optimization algorithm,it is to analyze the error of the optimization algorithm.In this paper,it is to get lightweight result with optimizing the plate thickness.As a pair of contradiction,lightweight optimization reduce the weight from 10.341t to 9.362t,while the vertical bending stiffness reduces by 9%and torsional rigidity reduces by 6%.Then rearranging the plate angle is to make up the stiffness reduction.The vertical bending stiffness increases by 6%and torsional rigidity increases by 4%.At the same time,it can be known that the algorithm is suitable for these problems.This idea to optimize can provide a new way for structure optimization design.