Studies in Boundary Lubrication—II: Influence of Adsorbed Moisture Films on Coefficient of Static Friction Between Lubricated Surfaces
- 1 May 1948
- journal article
- research article
- Published by ASME International in Transactions of the American Society of Mechanical Engineers
- Vol. 70 (4) , 401-406
- https://doi.org/10.1115/1.4017752
Abstract
Extraordinarily high values of the coefficient of static friction between steel surfaces lubricated with straight chain normal hydrocarbons (heptane to decane) are shown to be due to a film of adsorbed moisture at the solid-liquid interface. Friction measurements on a highly refined paraffin-base oil applied to surfaces in equilibrium with a dry and a moist atmosphere, confirm this idea, the coefficient of friction being 0.35 for the dry and 0.6 for the moist lubricated surfaces. Friction measurements are recorded for four fundamentally different lubricant types on steel, brass, and glass in equilibrium with dry air and air of 75 per cent humidity, respectively. The friction is in all cases raised from 40 to 70 per cent in the high humidity, the effects being particularly pronounced on glass. The results of the tests provide an explanation for many of the discrepancies among oiliness results in the literature obtained by the static-friction method, and indicate that the humidity of the atmosphere plays a significant part in the mechanism of boundary lubrication.Keywords
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