Contact between Rough Surfaces

Abstract

The surface roughness has a large influence on many physical phenomena such as friction, wear, sealing, adhesion, and electrical as well as thermal contacts. Initially, if two bodies with rough surfaces are pressed together, the “real” contact area is much smaller than the “apparent” contact area. The size of the “real” contact area determines, for example, the electrical and thermal resistance between the bodies. The size of the contact area and the maximum stress ultimately determines the size of the wear particles and therefore the rate of wear. The size of the real contact area is also a crucial factor in frictional processes. The cause of frictional forces can be visualized as the fracturing of microscopic bonds between the contacting bodies. The fracture strength, and therefore the frictional force, should be, according to this viewpoint, approximately proportionally to the “real” contact area. In this chapter, we will investigate the dependence of the contact area, length, and overall configuration on the normal force.