Friction and wear of a spherical indenter under influence of out-of-plane ultrasonic oscillations

This paper presents an experimental and theoretical investigation of friction and wear of a spherical indenter. With the pin-on-disc-tribometer the out-of-plane oscillations are applied to the sliding indenter. Oscillations lead to a decrease of the coefficient of friction, and this effect is also related to the sliding velocity and oscillation amplitude. During the sliding movement, the contact area of indenter increases due to the wear of material. This radius of the worn spherical cap is measured after each sliding period. It is found that the radius of the wear flat increases with sliding distance according to a power law with the power 1/4 and is independent of the sliding velocity. It further is practically insensitive to the presence of oscillations. A theoretical analysis and a numerical simulation based on the method of dimensionality reduction are carried out, both describing the experimental data very well.