基于多目标优化的白车身结构轻量化设计

Lightweight Design of Body-in-white Structure Based on Multi-objective Optimization

白车身轻量化研究有利于提高整车性能和减少研发成本,首先建立了某乘用车白车身的有限元模型,接着根据仿真模型分别计算出与NVH、静刚度及正面碰撞安全性能相关的参数,模型各项指标均满足要求。其次,依据综合灵敏度分析思路筛出与碰撞安全无关的设计变量,并且参照能量吸收曲线图选出正面碰撞安全板件的设计变量。针对白车身非碰撞安全相关板件的轻量化设计,根据试验设计方法设计出样本点,对比各类近似模型的精度,采用了椭圆基近似模型,将白车身质量最小、低阶模态最大作为设计目标,把白车身的静态扭转刚度以及静态弯曲刚度作为设计的约束条件,并采用遗传算法对非碰撞安全板件进行多目标优化。针对白车身正面碰撞安全相关板件的轻量化设计,根据试验设计方法设计出样本点,对比各种近似模型的精度,采用了响应面模型,将白车身质量最小、乘员舱加速度峰值最小作为设计目标,将一阶弯曲和一阶扭转模态频率、静态弯曲扭转刚度作为设计的约束条件,并采用遗传算法对碰撞安全板件进行多目标优化。最后,对轻量化前后的性能参数进行比较分析,实现了白车身质量降低13.4kg,降幅3.32%,轻量化系数减小了1,不仅保证了静态弯曲刚度和扭转刚度、白车身的模态频率各项指标基本不变,并且提高了白车身正面碰撞性能。结果表明基于多目标优化的白车身结构轻量化设计的减重效果较好,对车身的轻量化设计具有一定的参考意义与指导价值。

The lightweight research of body-in-white was beneficial to improve the performance of the vehicle and reduce the cost of research.Firstly,the finite element model of the passenger car's body-in-white was established,then the related parameters of NVH,static stiffness,and frontal collision safety performance were figured out separately based on the simulation model,all model targets were proved to meet the requirements.Secondly,according to the comprehensive sensitivity analysis ideas results,the design variables of irrelevant collision safety parts were comprehensively selected,and the design variables of the front collision safety parts were filtered out consulting the energy absorption curve.With regard to the lightweight design of the non-collision safety related parts of the body-in-white,the sample points were designed according to the experimental design methods,and the accuracy of various approximate models was compared mutually,an elliptical basis function approximation model was finally adopted.The minimum mass of the body-in-white,the maximum low order modals frequency of the body-in-white were set as the design goals,the static bending stiffness and static torsional stiffness of the body-in-white were set as the constraints of the design,and the genetic algorithm was adopted on the multi-objective optimization of the non-collision safety parts.With regard to the lightweight design of the BIW’s front collision safety parts,the sample points were designed on the basis of experimental design methods,and the accuracy of various approximate models was compared mutually,the response surface model was finally adopted.The minimum body-in-white mass and the minimum acceleration peak value of the left and right passenger compartments were set as the design goals,the first-order bending modal frequency and the first-order torsion modal frequency of the body-in-white,the static torsional stiffness and static bending stiffness of the body-in-white were set as the constraints of the design,and the genetic algorithm was adopted for the multi-objective optimization of the front collision safety parts.Finally,the performance parameters of body-in-white before and after lightweight design were compared and analyzed,which achieved that the weight of BIW was decreased by 3.32%,the quantity was 13.4kg,the lightweight factor was decreased by 1,not only all substantially unchanged indicators of the BIW’s modal frequency,static bending stiffness and torsional stiffness were guaranteed,but also the frontal collision performance of BIW was improved.The research results indicated that the lightweight design of body-in-white structure based on multi-objective optimization had a good lightweight effect,this paper had a certain referenced significance and guiding value for the lightweight design of the car body.