A simplified approach to the adhesive theory of friction

In the present paper, a simplified approach to the adhesive theory of friction, which encompasses both the concept of work of adhesion and the growth of the real area of contact, is presented. The starting point is to consider the average shear strength of the asperity junctions as dependent on the effective work of adhesion, which is influenced by the thermodynamic work of adhesion and irreversible local phenomena. Simple analytical equations for the average shear strength and friction coefficient are thus obtained, and their validity is checked with reference to experimental data relevant to copper and aluminum alloys dry sliding against high strength steel counterfaces. It is further shown that this approach is able to rationalize the presence and intensity of the oscillations on the friction trace (the so-called stick-slip phenomenon), and the influence of the initial roughness of the mated materials on friction evolution.