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

• Contact phenomena between rubber and glass are studied optically.
• The optically obtained sliding velocity field was linked to the measured friction force.
• The detachment processes of the tyre tread blocks and sipes were identified using DIC.
• The definition of sliding state of contact depends on length scale under observation.

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.

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