Effects of metal removal and residual stress on the contact fatigue life of railway wheels

Damage often occurs on the surface of railway wheel by the wheel–rail contact fatigue. Since the wheel failure may result in the derailment causing detrimental loss of life and property, the damaged surface should be removed prior to wheel failure. The increase or decrease of contact fatigue life by the metal removal of the contact surface was shown by many researchers, however, it has not been clearly explained the reason why the fatigue life changes. In this study, the effect of metal removal depth on the contact fatigue life has been evaluated by applying finite element analyses and conducting corresponding fatigue test. It has been revealed that the residual stress and the plastic flow are major factors determining the fatigue life. The railway wheel has the initial residual stress formed during the manufacturing process, and this residual stress changes due to the thermal stress induced by braking. It has been observed that the residual stress determines the amount of metal removal depth for the optimal fatigue life. Also, effects of the residual stress and metal removal on the contact fatigue life have been estimated, and an equation is proposed to calculate the optimal metal removal depth for maximizing the contact fatigue life.