Effects of wear on contact area and dynamic sliding velocity

The effects of the contact area and degree of wear on the sliding friction of polytetrafluoroethylene (PTFE) samples were investigated using an inclined glass plane. The sliding velocity and contact area of the samples were evaluated as functions of the sliding length and angle of inclination. The sliding velocity decreased exponentially as the contact area increased due to the wear of the samples, suggesting that wear is significant in non-lubricated sliding friction with PTFE on glass. The sliding velocity increased toward a maximum during the early stages of sliding, and then decreased in the later stages. The increase in the velocity during the early stages of the experiment can be explained by acceleration due to gravity, and the subsequent decrease is attributed to an increase in the contact area and to the build-up of debris particles due to wear caused by frictional heating of the contact area of the sample.