Lightweight Design For Body In White Of An Electric Vehicle

The tendencies in automobile development are lightweight,electrification and intelligent network in current automobile industry.Through lightweight design for vehicles,not only the car performances,such as handling and dynamics can be improved,but also can reduce the energy consumption and pollution toward the environment.In another aspect,in consideration of the electrification of vehicles,the lighter mass the car possess means the more driving range the car can reach.And the body in white(BIW)is an important component of the whole vehicle,so it is evidently important to conduct lightweight design toward the BIW of electric vehicles.At present,there are three methodologies to conduct lightweight design about the BIW: structure optimal design,application of lightweight materials and advanced forming process.A BIW of a small electric car is regarded as research object in this paper,and used the methodology of sensitivity analysis to optimize the size of plate thickness.The method that application of lightweight material,Aluminium alloy,is also used to improve the structural performance of BIW and the effect results of lightweight design.Based on the BIW geometry model of original electrical vehicle,the FEA model of the BIW is established using the Hypermesh software.And finite element method is utilized to analyze stiffness and free mode performance of the BIW.Compared the analysis results and its displacement tendency,the accuracy of FEM is verified.Considering that the battery of the vehicle has a large percentage of mass,the FEM of power battery is also established,and then analyzed the influence the battery has on the stiffness and mode performance of the BIW.And the analysis results was also regarded as the basis of later optimization design.The majority of the BIW parts are primarily chosen to conduct the analysis work of mass,stiffness and mode sensitivity to the part thickness.And the sensitivity analysis results are regarded as the basis for selecting design variables,which improved the optimization efficiency of lightweight design of BIW.The optimization design variables are selected according to the sensitivity analysis results,and then are divided into four groups based on different mass and performance sensitivity,for which different lightweight design plan are created: material replacement,thickness decrease and thickness increase.And the lightweight design of BIW are conducted later.The stiffness and mode performance results before and after lightweight design are compared to verify the validity of this design.Then the thickness sizes are rounded off and the optimized sizes are obtained.The mass of BIW after lightweight design is 648.6 kg,decreasing by 27.8 kg that means 4.1% compared with the original BIW.Finally,this lightweight design effect is evaluated using the BIW lightweight coefficient that is widely used in automobile industry at present.