Microscopic Damage Analysis of Structural Strength and Fatigue Life of Rotor of Automotive Drive Motor Under Cyclic Operating Conditions

Abstract

In order to study the structural strength change of automotive drive motor rotor under different cyclic conditions, and the fatigue life change after considering the internal damage of rotor material from the microscopic point of view, the strength and life calculation of automotive drive motor rotor is carried out based on the theory related to thermal-mechanical coupling and microscopic damage mechanics. Firstly, uniaxial tensile tests were conducted on the specimens at different temperatures to obtain the mechanical parameters of the silicon steel material at the corresponding temperature; secondly, the damage parameters at the corresponding temperature were fitted by the finite element inverse calibration method, and the temperature distribution law of the motor rotor was obtained by CFD calculation; then, based on the material parameters and temperature data, the damage condition and fatigue life of the rotor under four different cyclic operating conditions were studied by the finite element method. The results show that under the rated cycle condition, the stress does not reach the yield limit of the silicon steel material, and the volume fraction of holes inside the rotor material is still the initial hole volume fraction; under the peak cycle condition and rated-peak cycle condition, although the magnitude of the stress and stress distribution of the rotor are almost the same, the equivalent plastic strain of the latter is larger than that of the former, and the corresponding hole volume fraction is also larger; under the limit cycle condition In the ultimate cycling condition, the stress, equivalent plastic strain and pore volume fraction of the rotor have increased more obviously than the first three; and under the same cycling condition, the fatigue life of the rotor is smaller than that without considering the internal damage of the material.