Study On The Fatigue Life Of The Driving Axie Assembly Gear Of Electric Vehicle

The drive axle assembly of electric vehicle is one of the main parts of the transmission system of the vehicle.Its performance and service life largely determine the operation stability and service life of the vehicle.At present,the main failure mode of the drive axle assembly is the fatigue failure of the main reducer gear under the long-term random load.Therefore,it is necessary to carry out a more accurate fatigue life estimation of the main reducer gear of the drive axle.The results can be used to evaluate the remaining life of the existing main reducer of the drive axle,and also can effectively guide the design and development of the main reducer,which are important both theoretically and practically.In this paper,the main reducer of an electric vehicle is taken as the research object.Firstly,the related theory of fatigue life calculation and the counting method of fatigue load are introduced.Through the analysis of various fatigue life estimation methods,the nominal stress method and fatigue cumulative damage theory are determined to calculate the fatigue life of the main reducer gear.According to the characteristics of contact stress generated by gear meshing,it is determined to use GCM counting method to count the random load received during the gear meshing process of the main reducer.Then,according to the vehicle driving equation,using the Chinese passenger vehicle driving conditions(CLTC-P)as the speed input,calculate the torque transmitted by the main reducer gear,and the contact stress time history of the gear mesh is obtained by using the formula of the contact fatigue strength of the gear tooth surface,and the GCM counting method is used to deal with it,and the fatigue load spectrum of the gear that can be used for theoretical calculation is obtained.According to the contact fatigue S-N curve of gear materials,considering a variety of factors that affect the fatigue strength of mechanical parts,it is modified to the contact fatigue S-N curve of gear parts.The fatigue life of the main reducer gear is calculated by using the nominal stress method and the fatigue cumulative damage theory.The result shows that the driving mileage life of the main reducer gear is 482000 km when the contact fatigue break occurs.Finally,a test vehicle is used to do the actual road following test,collect the actual driving speed of the vehicle,and calculate the input torque of the main reducer gear by the vehicle driving equation.The three-dimensional software CATIA is used to model the main reducer gear to obtain the main reducer gear meshing assembly,which is then imported into ANSYS/Workbench to perform static simulation of the gear to obtain the contact stress generated by the gear pair meshing.The contact fatigue life of the gears is analyzed and calculated using ANSYS n Code Design Life,and obtained that the driving mileage life of the main reducer gears under CLTC-P driving condition is 494000 km,and the driving mileage life under the measured driving condition is 458000 km.The calculation results under the two conditions are compared,with the difference of 5.2% and 7.8%,respectively.Therefore,it is feasibility to calculate the fatigue life of the main reducer gear based on CLTC-P driving condition.