Friction Due to Elastic-Plastic Contact of Rough Surfaces

A three dimensional model based on CEB elastic-plastic contact leads to the derivation of two force components due to the shoulder-shoulder interaction of the asperities. A normal force component is resulted that upon summation of all possible interactions, in a statistical sense, obtains the normal force between the two surfaces. A second component of asperity force would be along the tangential plane (mean plane). When there is not net applied tangential force the tangential component of force on an asperity due to all its interactions would vanish. Upon impending motion, however, the tangential force can no longer cancel since the existence of a net tangential applied load would disrupt the symmetry of loading in the tangential direction. A three dimensional elastic-plastic model then furnishes a half-plane tangential elastic-plastic force term that would exist when relative movement of one surface on another occurs along an arbitrary axis in the tangential plane. This paper addresses an account of friction due to the elastic-plastic interaction of two surfaces by recognizing that the tangential half-plane elasto-plastic force term is the resisting force when two surfaces in elastic-plastic contact are made to slide.