The Lightweight Research Of New Energy Bus Body Frame Based On Finite Element Analysis

Aiming at the disadvantages of short range and short battery life of a new energy passenger car produced by an enterprise.Through the research on the production process of passenger cars and social practice experience,it is found that the body frame can account for40-50% of the weight of passenger cars.Lightweight body frame design can reduce energy consumption and improve the overall performance of the vehicle.According to the finite element analysis theory,the computer aided approximate numerical segmentation method is adopted.Taking the low order bending frequency,torsional frequency and torsional stiffness as the constraint conditions,a modern optimization scheme based on comprehensive performance analysis is proposed,which is the main research content of this paper.Firstly,based on the design theory of the body frame and related drawings,a 3d model conforming to the real situation is established based on the CATIA platform,and necessary geometric cleaning is carried out for subsequent calculation accuracy and efficiency.Based on the Hyper Works platform,an effective approximate numerical analysis model of the structure was established based on the ideas of "structural decentralization" and "integration of zeros into integrals",and the backward and forward preprocessing of the load distribution was investigated.The structural stiffness and strength under four typical working conditions were analyzed and solved by using Opti Struct to obtain the corresponding flexural and torsional stiffness,and the overall static performance of the skeleton was evaluated.In addition,the dynamic characteristics of the whole system formed by the skeleton are studied.The first ten free modes are extracted by means of modal analysis,the modal parameters of the system are identified,and the natural vibration characteristics are evaluated.The result of finite element analysis shows that the frame structure is good and the resonance excitation is avoided.According to the results of stiffness and strength analysis,reasonable optimization variables and objective functions are designed,with the minimum mass as the objective,and the stiffness,strength,density and wall thickness of the structure as the design variables,and the final lightweight scheme is determined.Considering such factors as Young's modulus,yield limit,density and production conditions,6061 aluminum is used as the choice of lightweight material.Based on the theory of relative sensitivity analysis,with the thickness as the design variable,the mass as the minimum as the objective function,the members whose relative sensitivity of stiffness is less than that of mass are selected for size optimization design.Finally,after analysis and calculation,the body frame of the whole vehicle can achieve weight reduction of 256 kg,with a weight reduction ratio of 7.39%.After weight reduction,the maximum stress does not exceed 305 MPa,which is less than the material yield limit.After calculation and verification,the structure performance of the vehicle is safe and the lightweight effect is good.