Gear transmissions have high power-to-weight ratios, can be made very compact and match the speeds and torques of one machine to another with high efficiency. However, gears are one of the weakest links in a transmission and can develop a number of failures (wear, contact fatigue, bending fatigue, etc.) which downgrade the overall transmission performance. The objective of this work is twofold; on the one hand, simulate abrasive wear on tooth flanks and contact fatigue leading to pitting, on the other hand, analyse the interactions between these damages and the dynamic and static behaviour of geared transmissions. To this end, a three dimensional gear dynamic model is used and coupled with several wear and fatigue models. The wear on tooth flanks is simulated based on a modified Archard’s law which includes the influence of the lubrication regime. Wear is accounted for via time- and position-varying distributions of normal deviations with respect to ideal flank geometry which are superimposed on profile and lead modifications. The occurrence of pitting is divided into two periods: a) a crack initiation period simulated by using several multi-axial fatigue criteria and, b) a crack propagation phase which is tackled using the theory of linear elastic rupture mechanics. The dynamic tooth loads delivered by the gear dynamic model are used as input data for the simulations of crack initiation and then crack propagation. A number of results are presented and the interactions between wear, contact fatigue and dynamic behaviour are investigated and commented upon.
