Friction Apparatus for Very Low-Speed Sliding Studies

Abstract

The phenomenon of stick-slip, which manifests itself in the squeaking of rubbing surfaces and is of considerable practical importance, can be advantageously studied at very low sliding speeds. An apparatus has been developed in which a flat surface is driven at speeds on the order of 10−7 to 10−4 cm/sec, the driving force being a weight. The speed is controlled by the viscous drag of a paddle in a bath of pitch. There is no appreciable elastic restraint in this drive, so that stick-slip vibration of the moving surface does not occur. A stationary rider is pressed against the moving surface by a dead weight. The friction is measured by the elastic deflection of a ring, the stiffness of which controls the tendency of the rider toward stick-slip vibration. Results are briefly described.