Lightweight Design Based On Optimization Of Body Joint And Development Of Joint Stiffness Experimental Device

The continuous development of the automobile industry greatly facilitates people’s travel,but also brings a variety of problems such as energy crisis,climate warming,environmental pollution.And at the present stage,car lightweight is an effective way to reduce fuel consumption and reduce carbon emissions.Body joint stiffness is about 50-80%of the stiffness of the whole vehicle body,and its performance has an important effect on the performance of the whole body in white.It has a certain reference value for the car body lightweight design through the structural optimization of the body joint to achieve the body lightweight.And developing the experimental device suitable for measuring the stiffness of the passenger car body joint is of great significance to guide the experimental study on joint.This paper set one certain car in the market as the research subject,and established the detailed finite element stiffness model.And summarizes the problems that should be paid attention to in the process of building the detailed finite element model,such as the simplified processing of the structure,meshing,and the element quality control.And the respective finite element model of body stiffness was established by replacing the individual joints of the vehicle body with rigid elements.By analyzing the finite element model of body stiffness,it is determined the size of the stiffness and whether the stiffness of the vehicle body is reasonable.The respective model with different joint is replaced by rigid element is calculated,and the sensitivity of the body stiffness to different joint is investigated by defining the concept of global stiffness ratio.The results of the analysis are compared,and up A-pillar joint of car body is confirmed as the optimization design research object.Several common methods of structural optimization are introduced.The variable density topological optimization was applied to optimize the structure of up A-pillar joint meshed by hexahedral elements.According to the topology optimization results,six optimization schemes were established,and the stiffness and global stiffness ratio of the vehicle body under different schemes was calculated respectively.Sensitivity of body stiffness to plate thickness for parts of body parts other than joints on up-A-pillar is analyzed,and the plate with high sensitivity and low sensitivity is selected to optimize the thickness of the body under the condition of keeping the same stiffness of body incorporated different structural joint to achieve lightweight body.Considering the results of weight reduction and stiffness analysis,the scheme of reinforcing plate thickness of 1.2mm,lap thickness of 1.2mm is identified as the best of six schemes.The stiffness analysis theory of the body joint is briefly introduced,and the finite element analysis of the A-pillar joint is carried out.Based on the theory of body joint stiffness analysis,a set of experimental devices for measuring the stiffness of passenger car body joints is designed,including the mechanical structure design and the electronic control software development.Finally,the stiffness of the body joints of SGMW is tested,and the reason of the deviation between the experimental results and the simulation results is analyzed.