Experimental Measurements of the Rest-Slope and Steady Torque on Ball Bearings Experiencing Small Angular Rotations

Abstract

Ball bearings experiencing small angular oscillations have been shown to trace out hysteresis loops. The hysteresis torque of ball bearings can be characterized by two parameters: the steady rolling friction torque T_s and the rest slope σ. Accurate prediction of these parameters is crucially important to designers, as the control of slowly rotating systems that use ball bearings is often dependent on hysteresis torque. This paper contains the development of an empirical expression for σ and a series of experimental investigations which establish and confirm relationships for the rest slope and steady torque behavior. Furthermore, the dependence of σ and T_s on the ball diameter is discussed. Excellent correlation is found between theoretical predictions and experiments conducted on an elementary three-ball system specially designed to determine rest-slope and steady torque values.