Stiffness Analysis And Research Of Joint Structure For Car Body In White

Joints are an important part of the white body frame structure,which have the effect of smooth transition.If the flexibility of joints are ignored and joints are treated as rigid body,it will increase additionally the rigidity of BIW.At the same time,joint stiffness is also of important factors influencing the stiffness of BIW.Thus,it is necessary to explore joints of BIW,which can provide reference for the design of BIW.This paper mainly research on unitary construction body.The dynamic and static performance of BIW was analyzed on the basis of the finite element model of BIW.Joint stiffness was calculated under the premise of considering fully flexible joints.Then the method of evaluating joint stiffness was explored and joint stiffness of BIW was evaluated.The relationship between dynamic and static performance of BIW and joints was discussed,and the influence of different joints on dynamic and static performance of BIW was obtained.This paper firstly established finite element model of BIW based on principles of finite element modeling.Bending stiffness,torsion stiffness,first-order bending frequency and first-order torsion frequency were calculated.The result of the evaluation was that the BIW has good bending stiffness,insufficient torsion stiffness and reasonable modal distribution.First-order torsion frequency was low relatively,which was prone to resonance due to coupling with excitation frequency of engine.The important parts which affect dynamic and static performance of BIW were concluded through the sensitivity analysis.Then seven joints finite element model of BIW were extracted,and it’s mechanical property was explored.There is coupling phenomenon in angular displacement matrix of joints through finite element analysis.The decoupling method and its flexibility were further explored in order to eliminate coupling phenomenon of joints model.Thus,the front and back stiffness,torsion stiffness and internal and external bending stiffness of joints were obtained.Secondly,the method of evaluating joint stiffness was explored,and joints and rigid joints of finite element model were established.Seven joint stiffness of each branch was evaluated through calculating stiffness ratio coefficient of joints branches for different joints.Then the front and back stiffness,torsion stiffness and internal and external bending stiffness of seven joints model for each branch were evaluated.Meanwhile,the stiffness of all joints branches under the same stiffness condition was compared.Joints branches with high and low stiffness ratio coefficient under the front and back stiffness,torsion stiffness and internal and external bending stiffness were summarized.Finally,the relationship between joints and dynamic and static performance of BIW was explored.The influence of different joints on dynamic and static performance was obtained through regional sensitivity analysis and strain energy calculation.Joints which have great influence on dynamic and static performance of BIW were summarized.At the same time,the important joints can provide reference for improving the performance of BIW.