Lightweight Research On Body-in-white Structure

With the development of the times and the improvement of people's living standards,the number of automobile ownership is constantly increasing.The national policy puts more and more strict requirements on the performance of automobile emissions and safety.The car is moving towards the direction of greenness,environmental protection and electrification,safety,comfortability and intelligence,which is constantly developing,and the lightweight body can effectively solve the problems of energy consumption,environmental protection and safety encountered by the automotive industry.The lightweight of the body-in-white structure is also highly concerned by academic researchers and major automobile companies.Firstly,this paper took body-in-white of the passenger vehicle as the research object,the body-in-white model under various working conditions was established and the low-order modal frequency of the body-in-white,static bending and torsional stiffness,the acceleration peak of the left and right passenger compartments were analyzed,and according to the comparison of the corresponding target values,the reliability of the model was verified.Secondly,the finite element software was used to establish the simulation model under the sensitivity analysis condition,and the direct sensitivity and relative sensitivity of the body-in-white components were obtained.According to the sensitivity analysis results,the thickness of 23 non-collision safety components were selected as the design variables.According to the energy absorption curve,the five components thickness variables with large energy absorption space and one material variable were selected as the design variables of the frontal collision safety components.Then,the lightweight of the body-in-white structure based on the multi-objective optimization was performed in parallel in two ways.for the lightweight design of the non-collision safety related parts of the body-in-white,the sufficient sample points of the non-collision safety-related parts design variables were designed by the optimal Latin hypercube design of experiment,and the accuracy of various approximate model methods was compared,the EBF approximation model was determined.The minimum mass of the body-in-white,the maximum first-order bending modal frequency and the first-order torsional modal frequency of the body-in-white were the design goals.The static bending stiffness and torsional stiffness of the body-in-white were the constraints of the design.Based on the NSGA-II,the multi-objective optimization of the body-in-white was carried out.The body-in-white performance and lightweight effect before and after optimization were compared and analyzed separately.The optimized mass is reduced by 8.6kg,compared with the original,the weight of body-in-white is reduced by 2.13%.Subsequently,for the lightweight design of the body-in-white frontal collision safety-related parts,according to the optimal Latin hypercube design of experiment method,enough sample points for the design parameters of the frontal collision safety-related parts were designed,and the accuracy of various approximate model methods was compared,the response surface model was determined.The minimum body-in-white mass and the minimum acceleration peak value of the left and right passenger compartments were the design goals,the static torsional stiffness of the body-in-white,the first-order bending modal frequency of the body-in-white and the first-order torsion modal frequency were the constraint of the design,and the multi-objective optimization based on the NSGA-II was used to compare and analyze the body-in-white performance and the weight-reduction effect before and after optimization.The optimized mass is reduced by 4.7kg,compared with the original,the weight of body-in-white was reduced by 1.16%.Finally,the final optimized design variables were taken into the original model to obtain the comprehensive analysis results,the performance before and after lightweight design was analyzed in comparison,the bending modal and torsional modal,bending stiffness and torsional stiffness of the body-in-white remained basically unchanged,the left and right passenger compartment acceleration peak value of the body-in-white had a certain degree of reduction,the frontal collision performance of body-in-white had a higher improvement,the weight of body-in-white was reduced by 13.3kg,the reduction was 3.29%,the light weight coefficient was reduced by 0.99,and the lightweight result of the body-in-white structure showed that the lightweight effect was good.The lightweight design of the vehicle body had a certain referenced and practical guiding significance.