Failure analysis of the conical press-fit connections in a locomotive drive system

The nose-suspension drive designs with overhanging pinion are commonly applied in freight electrical locomotives because of simple, space-saving and cost-effective. The failures of conical press-fit connections in a nose-suspension drive system are analyzed in this paper. It was showed by the analysis that the crack on the inner conical surface of motor shaft is initiated by the combination of fretting and corrosion. Sharp oil groove edge and emergency of crack at the mouth of radial oil hole in pinion will accelerate the formation of fretting wear groove, and consequently the initiation of cracks. Coexist of tensile normal stress under the contact surface within the fretting zone will benefit the propagation of the fretting fatigue cracks.