Digital Image Correlation to analyse stick–slip behaviour of tyre tread block

Stick–slip behaviour is a common but not entirely understood tribological phenomenon. The sliding motion of a rubber sample was studied on a glass plate. The local sliding velocity field of the contact area was calculated by means of Digital Image Correlation and compared to the measured friction force. It was observed that the sliding of individual sipes nucleates from the side edge, whereas the sliding of a tread block propagates from the leading edge. Phase shifts between tread block detachments were observed. Furthermore, a velocity field for a precursor is presented which indicates only the local sliding of the contact without the triggering of a global detachment. The relevance of the result for rougher surfaces is discussed.