ADHESION AND ADHESIONAL FRICTION AT THE CONTACT BETWEEN SOLIDS

The paper describes a theoretical study of adhesion and adhesional friction between solids with small-scale surface asperities using an elastic-plastic model of contact deformation. The well-established elastic and plastic adhesion indices are used to consider the different conditions that arise as a result of varying load and material parameters. From the predicted loading and unloading behaviour of solids, transitional values of the adhesion indices at which the influence of surface forces become insignificant are obtained. The results agree well with the existing experimental observations. The study also shows that, when the elastic adhesion index is low, the frictional force is almost proportional to the applied load. This may apply to solids with low elastic moduli. However, if the index is high the coefficient of friction depends on the applied load in the lower ranges and approaches a constant low value at higher loads.