Finite Element Analysis And Fatigue Life Prediction Of A Commerical Vehicle Body Structure

For the integrated body,the body is the installation foundation of the suspension system,the chassis system and the other accessories,and the load conditions are also complex.The performance of the body structure mainly includes: the inherent characteristics of the body,such as modal,bending stiffness and torsional stiffness;the static strength of the body;the connecting strength of key parts;the fatigue strength of the body.In the research and development stage of new automobile,it is an important factor for engineers to consider the performance of the body structure.The stiffness and NVH performance of the body directly affect the comfort of the automobile,and the static strength and fatigue strength of the body directly affect the life and property safety of occupants.Taking the integrated body structure of a commercial vehicle as research object in this thesis and carrying on finite element analysis of the body and prediction of fatigue life.Firstly,based on the finite element theory and software,the finite element model of BIW is established according to the geometric model of the body.And based on the theory of modal analysis,getting the vibration mode and frequency of BIW according to the modal analysis of BIW.The reasonable structure design of BIW is verified,and resonance is avoided under the low order excitation.Then,referring to the measurement method of stiffness test and the finite element simulation analysis,we can get the bending stiffness and torsional stiffness of BIW,which basically meet the requirements of target.Based on the results,the deformation of the openings of doors and windows in the bending and torsional conditions are calculated respectively,and it is found that the deformation of the openings meet the design targets.The results are basically consistent with the calculation and analysis of the bending stiffness and torsional stiffness.Next,based on the finite element model of BIW,the finite element model of the whole body is established.The peak force and torque of installation points of the body system and chassis system under extreme conditions are obtained through the simulation of Adams software,and the stress distribution of the whole body under extreme condition are calculated through the Abaqus software based on the inertia release method and considering the nonlinear factors.The results show that the body structure meets the strength design target.On the basis,the analysis of roof snow pressure is carried out,and the results show that the roof meets the requirement of resistance to snow pressure.Finally,the fatigue analysis theory and finite element fatigue analysis steps are introduced,and the three key factors of fatigue analysis are identified: S-N curve of the material,unit stress response and load spectrum.The fatigue analysis results of the body and spots are obtained through the fatigue analysis software.It is found that the maximum fatigue damage values of the body and spots are all less than 1,indicating that the body and spots meet the requirements of enterprise and the fatigue life of the reinforced road in the test field.This thesis applies CAE technology to analyze the strength,stiffness and fatigue life performance of the body structure.We can get the performance of the body structure and find the weak structure of the body in the stage of product development,and guide the optimization and analysis,shorten the development cycle and reduce the cost of research and development.The thesis also has some reference value and reference significance for the development of other automobiles.