Active Friction Control Using Ultrasonic Vibration

In this paper, the mechanism of reduction of friction by ultrasonic vibration has been studied. Experiments have been conducted by vibrating the specimen surfaces at ultrasonic frequencies. We found that vibration of the surfaces with amplitudes as low as a few nanometers evokes a super-lubricating effect when the frequency of vibration is high enough, here greater than 500 kHz. With a Pin-on-Flat (POF) test apparatus, a reduction of sliding (kinetic) friction was observed on surfaces vibrating laterally (inplane), vertically (out-of-plane) of ellipsoidally (both in-plane and out-of-plane components). Sliding a sharp tip of an Atomic Force Microscope (AFM) against a vibrating surface revealed near-zero friction. Whereas friction is reduced, we find that a dramatic increase in wear can occur when contact resonances are excited. Thus, contact resonance can be used for ultrasonic machining.