INVESTIGATIONS OF LOW-FREQUENCY STICK-SLIP MOTION - EXPERIMENTS AND NUMERICAL MODELING

Dry frictional contact between two steel surfaces in a harmonically fo rced spring-mass system is investigated both experimentally and numeri cally. The experimental set-up is somewhat novel in that the spring-ma ss system is excited through the frictional interface, facilitating de tailed study of interactions between the system's dynamic characterist ics and the stick-slip motion observed at the interface. A characteriz ation of the effect of wear upon observed stick-slip is given, resulti ng in the identification of three sliding regimes displaying varying d egrees of wear. Subsequent attention is focused primarily on the first of these regimes, the low wear regime, which features low frequency s tick-slip oscillations that can be measured quite reliably. This work particularly emphasizes the nature of transients entering and exiting stick phases, with several representations given of the evolution of t hese transients as control parameters are changed. Multiperiod and cha otic motions of the mass are also observed, with routes to chaos being qualitatively similar for a wide range of system parameters. The work also presents some numerical results in support of the experimental w ork, utilizing a rate- and state-dependent friction model proposed pre viously by the authors. It is seen that this model yields significantl y better predictions than can a simple Coulomb representation. (C) 199 8 Academic Press Limited.