The input shaft of gearbox usually bears a cyclic variation of torque, which may lead to the risk of experiencing a fatigue fracture. To evaluate the fatigue life accurately and identify the weak parts, the ANSYS is used to simulate the torsional fatigue of the input shaft for the gearbox, and the fatigue life of the weak part is obtained, which is then tested and verified by the torsional fatigue testing in the MTS torsional fatigue test rig. The test results show that the maximum difference is 14% between the calculated life and the testing results, indicating that the simulation value can reflect the actual fatigue life accurately. Notably, the cracks appear in the large oil holes, and its life is mainly concentrated in the crack initiation stage, accounting for 99.2% of the total life. The analysis results show that the fatigue life of the software simulation has the guiding significance for the life evaluation. The fatigue life of the shaft can be quickly calculated by the simulation to reduce the number of fatigue tests and achieve cost-effectiveness.

Gears are rotating mechanical parts with excellent power transmission efficiency and are widely used in machine tools, automobile, industrial machinery, and aviation industries. To enhance the performance of the gear, optimized design of the gear geometry is paramount. In this paper, we optimize the geometric tooth profile of helical gears which are among the gears of the transfer case gearbox by using the finite element program, Romax Designer to model and analyze the load and gear teeth of the gearbox power transmission system. The optimized gears were fabricated and compared to the results of the gear tests.