Atomistic Locking and Friction

Abstract

When solid bodies contact and slide against each other, frictional phenomenon occurs. The origin of the related friction force is studied by assuming the existence of two clean crystal surfaces, which follows the current experimental trends. This chapter theoretically clarifies the atomistic origin of the friction force intrinsically generated by the molecular interactions between the constituent atoms of solids, but not the force extrinsically generated by surface asperities, the existence of foreign atoms, and so on. It has been found that there are two origins as atomistic locking and dynamic locking. Atomistic locking occurs when the configuration of the atoms on a contact surface continuously changes with the siding distance and when the interatomic potentials have an arbitrary strength. In contrast, dynamic locking occurs when the configuration discontinuously changes due to the dynamic process and if the interatomic potential is stronger than a specific given value. A criterion is derived for the occurrence of dynamic locking. One other important finding prior to experiments is that certain unique cases exist where friction force exactly vanishes if completely clean solid surfaces are prepare.