Application of a two-dimensional model of continuous sliding friction to stick-slip

The authors have previously developed two-dimensional dynamic friction models for boundary and mixed lubricated line contacts, operating, under continuous sliding conditions. The performance of one of these friction models under intermittent sliding, involving stick-slip and slip-stick transitions is examined in this paper. The friction model includes the sliding velocity, the instantaneous separation of the sliding bodies, normal to the sliding direction, the normal load and fluid properties. The normal motions at the sliding contact were detected indirectly by contact resistance measurements which were, in turn related to the theoretical film thickness. It is known that at or near rest, a tangential contact stiffness and partial slip are observed, making it difficult to unambiguously identify a particular point at which slipping or sticking actually begins. Nevertheless, we investigate the applicability of a continuous sliding friction model to such situations. It becomes clear that normal motions play a critical role in determining the interaction between friction and vibration and that friction fluctuations into the sticking range can be described by the model as long as the duration of stick is not long.