Relation between friction and adhesion

Abstract

Simultaneous measurements have been, made of the friction and adhesion of steel sliding on indium in air. The results show that both the normal and tangential stresses play a part in the deformation of the metallic junctions formed at the interface. When the surfaces are first placed in contact, a minute tangential force is required to initiate relative motion between the slider and the indium surface, since the junctions are already plastic under the applied load. As relative motion proceeds, the region of contact grows with a corresponding increase in the tangential force and the adhesive force. An upper steady state is reached where the tangential force increases more rapidly than the rate of growth of the region of contact and sliding on a macroscopic scale occurs. The detailed behaviour of the junctions during the early stages of the sliding process may be expressed quantitatively in terms of von Mises's criterion for plastic deformation under combined normal and tangential stresses, and there is good agreement between the theoretical relation and the experimental observations. The results emphasize the reality of the cold welding process which occurs at the points of intimate contact when metal surfaces are placed together. The metallic junctions so formed are responsible both for the friction and the adhesion observed. Lubricant films diminish the amount of metallic contact and so lead to a reduction in the friction and adhesion.

A Comparison of Contact Stiffness Measurements Obtained by the Digital Image Correlation and Ultrasound Techniques

“…This may be due to a slight increase in contact area with tangential load owning to junction growth as first observed by McFarlane and Tabor [28]. This increase in contact area is small in comparison to that which would be expected in normal loading.…”

Tribological study of Fe–Cu–Cr–graphite alloy and cast iron railway brake shoes by pin-on-disc technique

“…Regarding the reduced friction at higher sliding velocities in the case of grey cast iron, this behavior can be explained in terms of reduction of the ploughing term of friction [16][17][18][19][20][21][22][23][24] for increased velocities.…”

Effect of adsorbed chlorine and oxygen on the shear strength of iron and copper junctions

“…One is the linear dependence of interfacial shear strength on adsorbate concentration expressed by equation (10). The other is the effect of junction growth on the adsorbate concentration expressed by equation (13).…”

“…One is the possible mechanism by which the presence of an adsorbate atom reduces the metallic bond strength. The other is the reason for the linear relation expressed by equation (10).…”