Study On Fatigue Performance Of Three-stage Drive Axle Shell Considering Preload

At present,most of the drive axle shells on the car are monolithic,but in order to adapt to the trend of vehicle electrification,the new three-section bridge shell has become one of the hot spots of car enterprise research and development,the three-section bridge shell is composed of the left end of the bridge shell,the middle powertrain shell,the right end of the bridge shell is composed of three parts,the bridge shell is connected by high-strength bolts between the three sections,so the bolt preload has a non-negligible impact on the three-section bridge shell,then the mechanical analysis method of the traditional integral bridge shell is not suitable for the research of the three-section bridge shell at this stage.Moreover,in order to meet the requirements of lightweight electric vehicles,the three-stage bridge shell has been initially developed to the development of aluminum alloy material for the powertrain shell.Therefore,considering the bolt pretension,it is a key problem to be able to estimate the fatigue life of the three-stage bridge shell in the current research stage.The main research contents carried out in this paper are as follows:(1)The layout of the rear axle of electric vehicle drive is analyzed,and the three-stage drive axle axle shell of the newly developed rear-drive coaxial axle is selected as the research object,and the geometric model of each component of the three-stage axle shell is constructed by using three-dimensional software,and then the geometric model of the bridge shell is assembled and imported into the finite element simulation platform,the material properties of the bridge shell are set and meshed,and the finite element model of the bridge shell is output after the mesh quality inspection is qualified.(2)Considering the actual working conditions of automobiles,the mechanical analysis of the drive axle shell under typical working conditions is carried out,and the stress and displacement clouds of the bridge shell under four working conditions are obtained,and the three-stage bridge shell under the maximum impact load condition is mechanically analyzed considering the bolt preload,so as to solve the stress and displacement distribution law of the bridge shell.After comparing the simulation results with the test results,it is known that when the bolt preload is considered,the relative error between the maximum displacement of the bridge shell simulation results and the maximum displacement of the test results is 5.4%,which is 17.7% lower than the relative error when the bolt pretension is not considered,thus verifying the feasibility of the mechanical analysis of the three-stage drive axle shell considering the preload.(3)The mechanical analysis results of the three-stage drive axle shell considering the bolt preload are transmitted to the fatigue analysis software,combined with Miner linear fatigue damage accumulation theory,the loading method of fatigue stress is defined according to the automotive industry standard,and the S-N curve of the material is corrected,and the fatigue life analysis of the bridge shell under the maximum shock load condition is carried out by the nominal stress method,and the fatigue life cloud of the three-stage bridge shell is obtained,so as to estimate the bridge shell life.(4)Vertical bending fatigue test on three-section drive axle housing.The results show that the fatigue life test result of vertical bending is 1 million times,and the fatigue fracture is located at the middle connecting flange,and the relative error of fatigue life is only 1.51% after comparison with the simulation results of the three-stage drive axle shell considering the preload force of 984,900 times,thus verifying the feasibility of the fatigue life analysis of the three-stage drive axle shell considering the preload.Therefore,this paper proposes that the mechanical analysis,fatigue life analysis and bench test analysis of the three-stage drive axle shell are carried out considering the bolt pretension,and then the feasibility of the fatigue performance study of the three-stage bridge shell considering the preload force is verified.This will provide a theoretical reference for the manufacture of multi-section drive axle axle shells in the future.