Micro-EHL Analysis of Ground and Superfinished Steel Discs Used to Simulate Gear Tooth Contacts

Abstract

This paper describes the results of a full micro-elastohydrodynamic lubrication (micro-EHL) analysis of steel discs. The first aim of the work was to compare the theoretical contact pressures and film thickness values for two significantly different types of surface finish. The first surface type was that of conventionally ground steel discs of a roughness value (Ra) of about 0.4 μm in which the direction of finish was transverse to that of lubricant entrainment. The second surface was that of a superfinished steel disc which had an Ra value of less than 0.1 μm. This comparison showed that, although the smoother surfaces gave a lower magnitude of pressure rippling in the contact than was the case with the rough surfaces, the minimum film thickness values were almost the same. A second aim of the work was to compare the contact pressure distribution under lubricated conditions with that obtained from dry contact simulation at the same load. It was found that the dry contact pressure provided a good approximation to that with a lubricant present under heavily loaded conditions and that the shape of the surfaces, in particular the depth-of-“valley” features of roughness, could be accurately predicted from a simple dry contact simulation.

Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996

KEY WORDS:

• Elastohydrodynamic Lubrication
• Gears

Notes

Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996