Research On Optimization Design Of The EMU Car Body Performance

The weight reduction of the vehicle body and improving its performance are an main subject in the process of railway vehicle design.Firstly,the optimization of car body can reduce the weight of the body,save raw materials,energy conservation and reduce driving costs;on the other hand,it can reduce interacting force between the wheel and rail,improve the dynamic and static performance of the car body,therefore it can also improve operational comfort,stability and safety.The main contents of this paper are as follows.(1)The finite element model of vehicle body is set up.The middle car body of CRH3 is taken as a researching object,the finite element model of car body is set up basing on the finite element theory.(2)The car body strength and stiffness are calculated.According to the European "EN12663" standard,the car body strength and stiffness of the six cases are calculated and analyzed and these are satisfied with the relevant standards.The modal of car body of both empty and preparation condition are calculated,the modal frequencies and eigenvectors are achieved.(3)The modal sensitivities of car body under preparation condition are calculated.The car body of preparation condition is taken as an objective,the plate thicknesses are taken as design variables,the number of design variables are 110,the carbody modal sensitivity of the first four orders under preparation condition are calculated using the numerical differential method.(4)The optimization design of car body are accomplished.Basing on sensitivity analysis,the first two order modal frequencies and carbody weight are each other taken as objective or constrain,the plate thicknesses of side wall,chassis,roof,chassis side beam are taken as design variables,the optimization designs with six schemes are accomplished using the feasible direction method.The first two modal frequencies are promoted and while the car body weight are reduced,the strength and stiffness of the optimized body are analyzed and the relative standard are meet.(5)The end wall sensitivities are analyzed.Basing on the optimized car body structure,the strength and deformation of the carbody under the compression cases on the end wall are calculated,the plate thicknesses of the end wall are taken as the design variables,the end wall is divided into 26 design variables,the sensitivities of the maximum stress on the design variables are calculated using the numerical differential method.(6)The optimization design of end wall are accomplished.Basing on sensitivity analysis of end wall,the end wall weight are taken as objective,the stresses of the end wall compression cases and the first two modes of the vehicle body are constrained,the optimization designs of end wall are accomplished.the strength and stiffness of the optimized body are analyzed and the relative standard are meet.Through the sensitivity analysis and multi-schemes car body structure optimization design,the first two modal frequencies are greatly improved,while the car body weight are reduced,and the carbody strength has been also improved.The weight reduction ratio is 5.71%,and the expect design objective is achieved.