Reduction of the sliding friction of metals by the application of longitudinal or transverse ultrasonic vibration

The influence on sliding friction of ultrasonic vibration both parallel and perpendicular to the sliding direction has been studied for samples of aluminium alloy, copper, brass and stainless steel sliding against tool steel. Experiments were performed at a mean sliding speed of 50 mm s−1, and at mean contact pressures up to 0.7 MPa, with vibration amplitudes up to 10 μm at 20 kHz. Significant reduction in sliding friction was observed (up to >80%) and good agreement was found between the measured values and the predictions of two simple models for the effects of longitudinal and transverse vibrations. Longitudinal vibration produces greater reduction in friction than transverse vibration at the same amplitude and frequency. At high vibration amplitudes, the reduction in friction was less than that predicted by the models, because significant metallic transfer occurred from the softer metals to the tool steel counter surface.