Characterisation of friction reduction with tangential ultrasonic vibrations using a SDOF model

Abstract

Active control of friction between sliding surfaces is of fundamental and practical interest in automotive applications. It has been shown that the friction force between sliding surfaces decreases when ultrasonic vibration is superimposed on the sliding motion. This principle can be applied to systems in which solid state lubrication or friction modulation is advantageous. The ultrasonic vibration may be applied longitudinally or normal to the direction of motion. A number of friction models have been considered in order to analyse this phenomenon. The degree of friction reduction has been shown to depend on the ratio of the sliding velocity to the vibration velocity. Since friction is a system response, it is necessary to include system dynamics in the analysis of ultrasonic lubrication. A nonlinear single-degree-offreedom-model is formulated and numerically approximated to quantify the effect on friction reduction of control force, intrinsic coefficient of friction, mass load, tangential contact stiffness at the sliding interface, and system stiffness. Model results are in close agreement with experimental measurements.