Abstract
The thicknesses of the films of lubricant formed between two steel discs in rolling and sliding contact have been estimated from measurements of the electrical capacity between the two discs. As the slide/roll ratio increased above a certain level the experimental values of the film thickness became progressively greater than the values predicted by conventional isothermal elastohydrodynamic theory. Ultimately the discs were operated satisfactorily with equal and opposite peripheral velocities, although the conventional theory would then predict the complete absence of a hydrodynamic film.
These discrepancies are observed when the peripheral velocities of the discs are in opposite directions and they are explained in principle by the effect of the variation of the temperature of the oil across the film in the inlet zone. The conventional theory of film thickness in elastohydrodynamic lubrication has been modified to take this effect into account.
It was not possible to obtain an exact theory for the general case but two extreme conditions could be defined and exact solutions found for them. Most of the experimental film thicknesses fell within the range of these extremes, and the variation with conditions of the position of the experimental points was approximately as expected on general grounds.
One of the consequences of these general considerations was that film thicknesses should increase with load at constant disc speed and surface temperature, and this was confirmed by direct measurement.
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