Torsional fretting fatigue strength of a shrink-fitted shaft with a grooved hub

Fretting causes considerable reduction in the fatigue strength of a shrink-fit assembly and failures through fretting are as numerous as failures from normal fatigue. The purpose of this investigation was to determine the effect of contact pressure and slip amplitude on the fatigue limit, and a favourable value for overhang of hub and fillet radius with constant diameter ratio, at which fretting failure can be avoided and the maximum normal fatigue strength will be obtained. The torsional fatigue strength of shrink-fitted shaft couplings was estimated by tests performed by varying the overhang of the hub, the fillet radius of the shaft and the contact pressure of the shrink-fitted assembly. Press-fitting of the hub overhanging the shoulder was used to increase the contact pressure. The tests were performed using a grooved hub. These experiments showed that fretting was reduced with an increase in contact pressure, because the slip amplitude decreased. The shaft was fractured just inside the end of the fit by fretting fatigue with low contact pressure, but if the contact pressure was very high, the shaft fractured at the fillet by normal fatigue. The fretting fatigue limit at a constant diameter ratio increases with an increase in the fillet radius, and reaches its maximum value at a certain radius using the grooved hub.