Fundamental Mechanical Aspects of Thin‐Film Lubrication

Abstract

SummaryThe paper highlights an extensive correlational study of the experimental evidence obtainable from literature on thin‐film lubrication. According to the widely varying nature of the various cases of thin‐film lubrication, this evidence is highly fragmentary and often seemingly incoherent. The main objective of the paper is to combine the evidence available into a coherent core of information on the fundamental mechanical aspects of thin‐film lubrication. From this core, continued research can profitably radiate in several directions, in the improvement of lubricants and the design of lubricated machine parts, for example. The objective set could be attained by introducing some unifying thoughts and theories in which dimensional analysis played an important role.The main conclusions, referring to the main and the supplementary theme, respectively, are: (1) any definitions of “oiliness” are inadequate that specify viscosity (even if its variations with temperature and pressure are included) as the one and only bulk property whose effects are to be eliminated in the measurement of “oiliness” as a surface‐active property, and a considerable improvement can be achieved by replacing the word “viscosity” in such definitions by the term “bulk properties of the lubricant and of the rubbing bodies”; and, (2) the core of information obtained can be turned to future advantage in settling the important question, “What are the limits inherent in hydrodynamic load‐carrying capacity?”