A model to study the effect of micropitting on the dynamic behaviour of a geared system

Abstract

Geared transmission systems operate under increasingly severe conditions that tend to promote micropitting on the gear flanks. Micropitting leads to an increased local coefficient of friction, in particular due to an increase in the average roughness of the damaged surfaces. Micropitting is hard to predict, but also hard to detect, since it mainly affects the contact conditions, which affect friction forces. On global signals such as input/output torque, these friction forces are one to two orders of magnitude lower than the normal forces and tend not to be detectable due to the noise in the experimental setup. This paper aims at studying the effect of micropitting on the vibrational levels of a geared system, by coupling the gear dynamics model developed by Osman and Velex with the roughness-dependent coefficient of friction formulation from Xu et al., and by representing micropitting by a local increase of the composite roughness. The simulations show that micropitting has a clear impact on the system dynamic behaviour, especially in the direction perpendicular to the plane of contact. Finally, it was shown that the bearing forces and the pinion acceleration are suitable candidates for micropitting detection, even with noisy signals.