Soft Metallic Films Research Articles

The coefficients of friction and wear

The combination of the Savage surface energy and the Bowden and Tabor junction formation mechanisms of production of frictional energy is suggested. The physical description of the experiments is sufficiently simplified and represented by a stable state which envelopes the whole field of friction. This leads to a qualitative and satisfactory agreement with the observed results for the values of coefficients of friction between solid surfaces, between solid surfaces with thin liquid or solid soft metal films, for wear, and for the correlation between friction and wear. The coefficient of wear is defined analogously to the coefficient of friction.

Frictronal Properties of Metallic Films

DR. HUGHES' S recent remarks1 would appear to be based on the three wrong premises that, first, films of soft metals wiped on to steel surfaces on which a loaded steel ball was made to rotate2 never decreased the electromotive force ; secondly, the interpretation of earlier observations3 on the frictional behaviour of such films on a copper surface made on the Bowden-Leben apparatus had been criticized; and thirdly, frictional decreases due to these films should be taken as an indication that changes in the ploughing contribution to the frictional force were immaterial when such decreases were observed “during the first slide” with the Bowden-Leben apparatus.

Letter to Editors

IN the light of Dr. Schnurmann's above remarks, it appears that he is still unconvinced by our original interpretation of frictional data1 on the Bowden-Leben apparatus, when a small steel spherical surface was slid over copper covered with thin films of soft metals (lead, cadmium and tin), and also by later additional experimental data2. It was originally suggested that the reduction in the coefficient of friction, µ, from 0.5 to 0.7 for steel on the bulk metals lead and copper, say, to 0.03–0.08 for films of lead, 10-5-10-6 cm. in depth, was due to the combination of a thin soft film on a hard substrate maintaining a small area of contact across which “the adhesion and deformation resistance” was very low. Dr. Schnurmann considers the effect is solely due to a reduction in the “ploughing action”.

Frictional Properties of Metallic Films

A RECENT communication by Schnurmann1 has criticized the interpretation of earlier observations2 on the frictional behaviour of thin films of soft metals on a copper surface made on the Bowden-Leben apparatus.