Fuller and Tabor model dependence of adhesion on surface roughness for elastic solids: where: K is the coefficient of reduction in adhesion by asperity deformation forces; E is the Young's modulus [Pa]; σ is the standard deviation of the asperity height distribution (RMS) [m]; r is the average radius of curvature of individual asperities [m]; Δg is the change in surface energy on contact between the two surfaces [J/m2]. It is assumed that for K < 10 strong adhesion occurs, while for K > 10 asperity deformation forces cause the net adhesion force for elastic materials to be small.

Schematic diagram of asperity junction growth under frictional force

where: F is the friction force [N]; W is the normal force (load) [N]; Ar is the real area of contact with tangential force present [m2]; Aro is the real area of contact in the absence of tangential force [m2].

Adhesion between gear teeth resulting in scuffing

The Delamination theory of Wear