A Theoretical View of Lubricated Friction

In looking at the basic mechanisms of lubricated sliding friction, the major emphasis falls on the adhesive process because a p/ilonj. it is the one most likely to be influenced by the presence of the lubricant at the rubbing interface. The mechanisms to be considered here in particular are those that make their effect felt in thin film or boundary lubrication. The action of macroscopic liquid films, generated hydrodynamically or otherwise, are not included in this treatment because the surfaces are completely separated from each other the meaning of friction in such cases is discussed in Chapter 2. 

Going back to the system represented by Eqn 9-2, the total real area of contact is 

Few experiments yielding data that can be applied to the quantitative demonstration of the mechanism of lubricated friction are on record in the literature. In the work of Rabinowicz and Tabor [11], radioactive transfer is used to evaluate metal-to-metal contact and adhesion in the sliding of copper against copper. The transfer data shown in Table 9-12 as nanograms of copper per cm of sliding distance are assigned a relative volume rating y, from which the relative area of the asperity junctions is computed as follows  

Using the results for dry rubbing as the base reference, the data are applied to the relation 

TABLE 9-13. PROPERTIES OF BOUNDARY-LUBRICATED JUNCTIONS FOR COPPER 

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