BIFURCATIONS FROM STEADY SLIDING TO STICK-SLIP IN BOUNDARY LUBRICATION

We explore the nature of the transitions between stick slip and steady sliding in models for boundary lubrication introduced in J. M. Carlso n and A. A. Batista, Phys. Rev. E 53, 4153 (1996). The models are base d on the rate and state approach which has been very successful in cha racterizing the behavior of dry interfaces [A. Ruina, J. Geophys. Res. 88, 10 359 (1983)]. Our models capture the key distinguishing feature s associated with surfaces separated by a few molecular layers of lubr icant. Here we find that the transition from steady sliding to stick s lip is typically discontinuous and sometimes hysteretic. When hysteres is is observed it is associated with a subcritical Hopf bifurcation. I n either case, we observe a sudden and discontinuous onset in the ampl itude of oscillations at the bifurcation point.