Abstract
IN lubrication, a fluid or other body is used to decrease the friction between opposed solid faces. The lubricant may act in one of two ways. It may separate the faces by a layer thick enough to substitute its own internal friction, modified by the mechanical conditions in which it finds itself, for that of the solid faces; or it may be present as a film, too thin to develop its properties when in mass, which reacts with the substance of the solid faces to confer upon them new physical properties. In the latter case the solid faces continue to influence each other, not directly, but through the intermediation of the film of lubricant. There are indications that these two types of lubrication— one in which the solid faces intervene only owing to their form, rate of movement, etc., and not by their chemical constitution; the other in which the chemical constitution is directly involved—are discontinuous states in that one cannot be changed gradually into the other by simply thinning the layer of lubricant. The change from the one to the other is probably abrupt.
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HARDY, W. Some Problems of Lubrication1. Nature 106, 569–572 (1920). https://doi.org/10.1038/106569a0
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DOI: https://doi.org/10.1038/106569a0