Area of Real Contact: Elastic and Plastic Deformations

Abstract

The friction force equals the shear stress integrated over the area ∆A of real contact. Because of surface roughness, the area of real contact is usually much smaller than the apparent area of contact. In this section we discuss the physical processes which determine the area of real contact and present some experimental methods which have been used to estimate∆A. In most practical applications, the diameter of the contact areas (junctions) are on the order of {\textasciitilde}10 $μ$m. However, the present drive towards microsystems, e.g., micromotors, has generated a great interest in the nature of nanoscale junctions. The physical processes which determine the formation and behavior of nanoscale junctions are quite different from those of microscale junctions. We consider first microscale junctions and then nanoscale junctions.