Lightweight Design Of Car Body Structure Based On The Passive Safety

As the pillar industry of the national economy,the automobile industry is closely related to the development of national economy and personal life.vehicles bring not only the convenience to people but also some social problems such as oil shortage,environmental pollution and so on.As one of the future trends of automobile development,automobile lightweight can effectively alleviate these problems.As the supporting body of the car,body-in-white is about one-quarter of the whole vehicle equipment quality.So lightweight design of body-in-white has great significance.In this paper,the white body structure of a new vehicle is optimized combining with the enterprise project.Considering the low order modes,bending stiffness,torsion stiffness and the safety performance of the front and side impact of the car,this paper puts forward the strategy of the white body structure lightweight design in three stages by using the surrogate model optimization technology,namely,multi-objective optimization of non safety parts,multi-objective optimization of side impact safety parts and multi-objective optimization of frontal crash safety parts.This strategy achieves remarkable lightweight effect.This paper mainly completed the following research work:1.The finite element model of BIW structure is established.Then,vehicle frontal crash and side impact simulation model is built using the module modeling method.Analyse the low order modes,bending stiffness,torsion stiffness of BIW and the vehicle frontal and side impact safety performance and compare with the real vehicle test data.The accuracy of the simulation model is proved to meet the requirements of the following optimization.2.According the transmission path of the impact force and the amount of energy absorbed during the frontal and side impact,body-in-white is divided into non-safety area,frontal crash safety area and side impact safety area.3.Analyse the relative sensitivity of the non-safety area parts,43 groups of optimization design variables are selected.Analyse the structural contribution of the frontal and side impact safety parts,20 sets of frontal crash safety parts and the 17 sets of side impact safety parts are selected as the following optimization design variables.4.The white body structure is divided into three stages to optimize by using the surrogate model optimization technology,namely multi-objective optimization of the non safety parts,the side impact safety parts and the frontal crash safety parts.Three stages of optimization design make white body weight loss 11.306 kg,2.349 kg and 3.430 kg respectively.The total weight loss reaches 17.085 kg and weight loss rate is 5.28%.5.After the lightweight design,the bending and torsion stiffness of BIW were increased by 8.82% and 1.66% respectively.The first order torsional and bending natural frequencies were increased by 1.54% and 0.45% respectively.At the same time,the passenger compartment peak acceleration of the vehicle frontal collision was reduced by 3.51%.The maximum intrusion of the front was reduced by 5.25%.Overall,the safety performance of vehicle frontal crash is slightly improved and the safety performance of side impact is the same as before the lightweight design.