An Experimental Study on the Accuracy of Cumulative Damage Models in Gear Tooth Bending Fatigue

Abstract

Tooth bending fatigue failure is a primary design concern for gear designers in power transmission applications. Fracture of a gear tooth in operation results in overload conditions to adjacent teeth, which cascades into potential failure. Total loss of power transmission usually occurs within seconds of the primary failure. While standard constant stress amplitude fatigue evaluations are common to experimentally determine probabilistic stress–life (PSN) relationships, they do not directly measure the fatigue lives under complex, non-constant amplitude loading scenarios applied to gears in most applications. Various cumulative damage models exist to estimate fatigue life under duty cycle loading, but their accuracy is both material and stress state dependent. Most models are validated under only uniaxial stress states and for limited materials. There is a void of experimental data that would enable the evaluation of the accuracy of cumulative damage models for gear tooth bending fatigue in typical cases of carburized gear steels. This research study conducts a standard fatigue evaluation along with two sets of dual stress amplitude single tooth bending fatigue tests to empirically determine the effects of multi-stage loading. Various cumulative damage fatigue models are then employed to estimate the fatigue lives of the dual stress amplitude specimens, and the accuracy of each model is assessed.