The friction force during stick-slip with velocity reversal

Abstract Stick-slip is the well-known phenomenom of intermittent motion caused by a changing friction force in combination with mechanical system elasticity. Usually, no velocity reversal occurs during the slip-phases of a stick-slip cycle. However, velocity reversal is observed during stick-slip motion of a laboratory test rig with oil lubricated centre-pivoted sliding shoes and a very flexible tangential spring connection. The general condition for velocity reversal during the slip-phase of a stick-slip cycle is derived and the friction force during stick-slip with velocity reversal is measured and discussed with reference to the Stribeck-curve, which represents the friction force in steady-state conditions. In order to better understand the friction force during velocity reversal, free vibration tests with friction are also performed and discussed in this paper.