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 μm, 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.
