The research is mainly about the fatigue life of the spur gear of the drive axle assembly of electric vehicles. Due to the limitations of personal ability, time, knowledge level and experimental conditions, there are some deficiencies in the calculation of the contact fatigue life of the spur gear of the main reducer under the driving conditions of Chinese passenger cars (CLTC-P) and the actual road conditions, which need further research and improvement:
(1) The compilation of load spectrum is the basis of fatigue life calculation, and the calculation accuracy of fatigue life largely depends on the accuracy of load spectrum. The common method to obtain the load spectrum of the spur gear of the main reducer is mainly obtained through dynamic simulation analysis and experiment. In this paper, the corresponding contact stress spectrum is obtained by using the CLTC-P road conditions and the actual road conditions through the vehicle driving equation and the calculation formula of the contact fatigue strength of the spur gear tooth surface. Because the actual collected road condition data is special and the contact stress spectrum is calculated by theoretical formula, the load spectrum used in this paper is different from the actual load time history of the spur gear of the main reducer. If conditions permit, the torque sensor can be installed on the input shaft of the spur gear of the main reducer to collect the load data, so as to obtain a relatively more accurate load spectrum.
(2) Obtaining the S-N curve of the spur gear of the main reducer is the key step to calculate its fatigue life by using the nominal stress method. The S-N curve of spur gear parts is obtained by modifying the S-N curve of the standard test bar of spur gear materials. The correction factor is affected by many factors, and its value is often selected approximately, which makes the S-N curve of the spur gear parts corrected have certain differences from the S-N curve under the actual working environment. Under the condition of experimental conditions, the test of spur gear parts can be carried out on a special test bench according to the specified process, and the contact S-N curve of spur gear parts can be obtained.