Abstract: In order to solve the low-cycle fatigue failure of main shaft of power-shift steering transmission, the dynamic torque of main shaft was measured during pavement testing, and the fatigue sample was analyzed. An elastoplastic finite element model of main shaft is established to predict the low-cycle fatigue life of main shaft. The low-cycle fatigue test of main shaft was made to verify the low-cycle fatigue life prediction method. The results show that the impulsive torque of tracked vehicle in starting stage is the main cause of low-cycle fatigue of main shaft. For the asymmetric structure, the impulsive torque on the right side of main shaft is about 1.54 times of that on the left side. The maximum stress of main shaft is 1 510 MPa, and the maximum strain is 0.008 692 3, both occur at the root of boundary between output spline and transition arc on the right side, which is consistent with the fatigue fracture location of fatigue sample. The number of main shaft withstanding the starting impact torque is 17 082, the number of main shafts withstanding the starting impact torque obtained by bench tests is 5 000, and the number of main shafts withstanding the starting impact torque obtained by low-cycle fatigue life prediction is 5 843. The simulated results are basically consistent with test results, which verifies the feasibility of the low-cycle fatigue life prediction method. Key

Key words: power-shiftsteeringtransmission, mainshaft, low-cyclefatigue, dynamictorquemeasurement