Study on Repair Fatigue Damage of Axle Shaft Mechanical Parts

Axle shaft is a most commonly axial mechanical part. Because of bearing bending and torsion loading at the same time, fatigue damage is a kind of common form to shaft part. So repair of fatigue is very important. In this paper, a theoretical model of fatigue damage of the materials was established, the value of the damage was calculated, the mechanism of fatigue damage and repairing of the shaft were studied in macro, meso and micro aspects. It was found that the segregated distributing of particles in the second phase of materials has played an important role in initiating, nucleating of fatigue damage, forming and expansion of micro-cracks. First of all, initiation of cracks is in the place of Cr-rich particles or with the Cr carbide particles in the second phase of material. Fatigue damage of the shaft is repaired by the way of heat treatment. Tests have been done in several aspects such as the choices of tempering opportunity, temperatures, methods, cooling and so on. After analysis to the results of the tests, it was found that there are some effects on the repair of fatigue damage of the shaft is different in different materials. The effect of repairing to the fatigue damage is more evident for the shaft made of 40Cr steel than that of 45steel. The accumulated fatigue life of the shaft has been raised by tempering. It was found that the materials can remember the tempering temperature that is used in the past. There is a temperature threshold in choosing tempering temperatures when repairing fatigue damage of the materials.