Numerical experiments consist in sliding a rectangular object along a fixed one, so that one edge of each object stay in contact with one edge of the other (Fig. 1). The relative displacement between the two sliding surfaces is calculated for different stages (Fig. 2). We also compute the obsolute motion through time of several points along the interfaces as well as the stresses in order to characterize the interactions between asperities during displacement (Fig. 3).

Figure 1: (a) Model configuration and (b) surface morphology. Model 1 has a regular surface morphology (sinusoidal) and model 2 has an irregular surface morphology. Points A and B are the points used to analyze the slip regime for model 1 and 2 respectively.

Figure 2: Computed slip distribution and stress perturbation for dx = 0.12 and dx = 0.32. There is a relationship between anomalies in slip (lows) and stress concentration. (a) A regular surface morphology (see animation model 1) has many contact points so the slip anomalies and stress concentrations less important. (b) Slip anomalies and stress concentrations are enhanced when the surface morphology is irregular (see animation model 2) with few contact points.

Figure 3: Slip regime for (a) the sinusoidal morphology (models 1) and (b) the irregular morphology (model 2). One single point is analyzed through time for each model (see figure 1 for location of points A and B of model 1 and 2 respectively). There is a stress increase where the points are blocked along a positive asperity. The slip is then reduced with a decreasing Dx (stick regime). There is a stress drop as soon as the point passes the top of the asperity. The point slips as seen by the increasing Dx (slip regime). The second order stick-slips are a mesh effect when two points are in contact.