EHL Film Thickness Research Articles

Specific Film Thickness—A Closer Examination of the Effects of EHL Film Thickness and Surface Roughness on Bearing Fatigue

Analysis of literature bearing-fatigue life results shows that fatigue life is not a simple function of the widely accepted specific film thickness, λ, which is the ratio of the EHL film thickness h to composite surface roughness [sgrave]. Instead, the influence of film thickness on bearing life increases with increasing surface roughness; at about 0.20 micrometer (8 microinch) composite roughness life increases with the square root of h while at about 0.46 micrometer (18 microinches) life increases with h squared. The negative effect of surface roughness on bearing life appears to be relatively independent of film thickness. This suggests that surface roughness affects fatigue life by some mechanism in addition to the degree of interaction of asperities through an intervening EHL film. Additional test results are needed to confirm this point.

Further developments in the inductive measurement of ehl film thickness

Further developments in the inductive measurement of ehl film thickness

Elastohydrodynamic properties of water in oil emulsions

Elastohydrodynamic (EHL) film thicknesses of emulsions have been measured in a rolling point contact using an optical interference method. Both water in oil and oil in water emulsions have been studied. For water in oil emulsions the experimental data suggest that EHL film thickness is almost independent of water concentration and also particle size distribution, although the bulk viscosity of the emulsions is heavily dependent upon these two variables. It is concluded that the EHL properties of such emulsions are determined almost entirely by the EHL properties of the pure oil. For oil in water emulsions, negligible EHL film formation was observed.

A re-examination of ehl film thickness measurements: GREENWOOD, J.A. Wear, Vol 15, No 4 (Apr 1970) pp 281–289

A re-examination of ehl film thickness measurements: GREENWOOD, J.A. Wear, Vol 15, No 4 (Apr 1970) pp 281–289

A re-examination of EHL film-thickness measurements

Published elasto-hydrodynamic film thickness measurements in pure rolling are compared with theory. The validity of Dowson and Higginson's formula as a general guide is demonstrated, even under conditions which should have favoured the classical Martin analysis. The experimental trends definitely contradict the theory and it seems doubtful whether the assumptions of isothermal theory are adequate.