SAE International Influence of In-Plane and Out-of-Plane Ultrasonic Oscillations on Sliding Friction 2011-01-2361

Vibrations of varying frequency and amplitude are used in many technological areas to control friction. In this study we report the most comprehensive results of high precision measurements of the sliding friction as a function of ultrasonic oscillations. The friction force between a steel plate and a steel sample oscillating in sliding direction, perpendicular to the sliding direction, and perpendicular to the sliding plane at a frequency of 30-50 kHz has been studied. We have found that for dry friction in the absence of vibrations, it is characteristic that the frictional force slightly decreases as the velocity increases. The friction coefficient is a monotonically decreasing function of the sliding velocity. However, it will be shown, that if we excite the system using ultrasonic oscillations with an amplitude of about 0.1 \u03bcm, the frictional force becomes a monotonically increasing function of the sliding velocity. This effect can be used to suppress frictionally induced instabilities and thus might be used as a mechanism to suppress braking noises. Additionally it is shown that the friction coefficient is significantly decreased in value. The largest reduction of the friction coefficient is reached for small velocities at high amplitudes.