Lightweight Design Of Pure Electric Automobiles' Body Based On Stiffness And Modal Analysis

The rapid development of automobile industry will obviously bring some adverse influence to the society.Based on the significant effect in the field of environmental protection and energy saving,automobile lightweight technology will play an important role in the development of automobile industry.For pure electric automobiles,their lightweight design on the body is not only able to produce the benefits of energy conservation and environmental protection,but also can significantly improve their mileage.the properties of modal frequency,stiffness,strength of the white body structure and the comfort,safety and durability of the automotive indexes are closely linked.so it is necessary to analyze the static performance of the body.In this paper,based on the research results of the predecessors,the modal,strength and stiffness of pure electric automobile body are synthetically taken into consideration.In the process of the lightweight optimization design,this paper combines the response surface approximation model technique and particle swarm optimization algorithm,finally achieves the effect of lightweight on the premise of not reducing the comprehensive performance of the automobile.In light of the theme of body lightweighting,this paper mainly carries out the following researches.(1)The finite element model of body is established and its properties of modal,strength,bending stiffness and torsional stiffness in the static state are analyzed,gets the first six order modal frequency values,static bending stiffness and static torsional stiffness,and the static strength of body in three kinds of typical working conditions are analyzed,which makes a good preparation for the following lightweight optimization design.(2)The 14 components of the bottom floor beam section structure of body are chosen as the target parts,and 10 thickness design variables are set up.The experiment design is carried out in the Optimal Latin hypercube design method,and 150 sample points are extracted.With the mass,modal,bending stiffness and torsional stiffness of body for the response,the sample points are calculated to get the values of all the responses.The variables and the corresponding response datas are fitted to the third-order response surface approximation model.(3)Setting the minimum mass of body as the object,the modal,the bending stiffness and torsional stiffness as the constrains,the particle swarm optimization algorithm is applied to the global optimization.Finally,the optimal combination of the thickness of the variable components is obtained.The optimized finite element model is reestablished,and the optimized response values are calculated to verify the fitting effect of the optimized result.The values of all the responses before and after optimization are used to verify the effect of achieving lightweight.The optimization result show that the mass of the bottom floor beam section structure has been reduced by 12%,which leads to reduce the mass of body structure by 1.45%,so the effect of lightweight is achieved.