Dislocation Structure and Stick–Slip Phenomenon

Friction is a complex process involving multi-scale asperity contact and large plastic deformation associated with the development of a dislocation structure. Friction is closely associated with the stick–slip phenomenon. In spite of the large number of papers, dedicated to stick–slip effects, little effort has been directed toward elucidating the development of the dislocation structure during stick–slip phenomena. Here, we report some new systematic investigations into the dislocation nature of stick–slips during low-velocity friction of a lithium fluoride single crystal rubbed against a spherical diamond indenter. It is shown that the average velocity of the indenter in the stick phase is about 300 times lower than the maximal velocity in the slip. This difference in velocities leads to entirely different dislocation behavior and damage development in the stick and slips phases. The stick phase is mainly determined by time-dependent strain (creep) wherein, as in metals and alloys, three stages of creep are observed. Based on the analysis of the dislocation structure, a model of the dislocation distribution in the regions of stick (creep) and slip is proposed.