Finite Element Analysis And Lightweight Design Of A Tourist Bus Body Frame

With the rapid development of the automotive industry,the problem of vehicle energy saving and emission reduction is attracting more and more attention.Vehicle lightweight is one of the effective ways to achieve energy saving and emission reduction in the automotive industry.It has become the main direction of automotive technology development in current days and the future.This article takes an integral long-distance sightseeing coach body of a famous automobile enterprise in China as the research object.On the basis of investigating the relevant research results at home and abroad,by means of simulation analysis and real vehicle test,the strength,stiffness and modal analysis of the whole frame are carried out,and the lightweight design of the whole vehicle skeleton is also carried out.The main contents are as follows:Build up the coach body skeleton geometry model through large-scale 3D modeling software CATIA,and import it into finite element software Hypermesh for model simplification,mid-plane extraction,meshing,connection processing,and attribute assignment,thereby establishing a complete body skeleton finite element model.Four types of typical conditions such as full load bending,emergency braking,limit torsion,and emergency turning in the routine operation of a coach are set with corresponding constraints and loads,strength and stiffness analysis shows that the maximum stress value of the entire vehicle frame is 290.7 MPa,and the maximum displacement value is 23.86 mm,which do not exceed the limit that the material can withstand,meets the strength and stiffness requirements,and there is a certain margin.Strain electrical measurement method is used to measure the entire vehicle skeleton under full load still working conditions,compared the test results with the results of finite element calculations,the results show that the error between the two is less than 10%,with high consistency,verifying the accuracy of the finite element model.The modal analysis of the vehicle skeleton is performed using the Block Lanczos calculation method and get the first eight-order free modal frequencies,which is higher than the road excitation frequency 3Hz and lower than the engine idling frequency 37.5Hz,avoiding the resonance phenomenon.The paper also tried the restrained modal analysis of the vehicle under full load conditions.Taking the thickness of the profile as the design variable and the minimum mass of the entire vehicle as the optimization goal,the maximum equivalent stress is lower than the allowable stress of the material as the constraint condition,and an optimization mathematical model is established,based on the sensitivity analysis,the structure of the bar with less stress on the whole coach frame was optimized,resulting in a reduction of the body frame of 87Kg,which accounted for 5.04%of the total car frame quality.At the same time,the strength,stiffness,and modal analysis of the optimized body are performed.The results show that the lightweight vehicle skeleton meets the static and dynamic characteristics requirements.The lightweight program is feasible and provides some guidance for the light weight design of the same type of passenger cars in the future.