Abstract
The frictional motion of a linear array of parallel identical cylinders on a horizontal plane is studied both experimentally and analytically. An "irregular" stick-slip motion is observed in experiments. However, statistics on the forces before and after each slip show stable average behavior. We find that global dynamic and static coeKcients of friction of the system increase with the number of particles. The organization of the rotations of particles appears as regions with characteristic lengths intermediate between the particle size and the size of the system. The mechanisms leading to these spatial patterns are studied analytically and are shown to be related to the interplay of the Coulombic friction law and the geometrical frustration of rotations. A simple argument based on the variation of the global friction force with the applied force on the array is proposed to account for the slip amplitude distributions observed in experiments.