The Stribeck curve plays an important role in identifying boundary, mixed, elastohydrodynamic, and hydrodynamic lubrication regimes. Recent advances in elastohydrodynamic lubrication together with rough surface interaction have made it possible to develop a methodology for predicting the trend of the Stribeck curve. In this paper; we report the results of a series of experiments performed on a journal bearing together with a theoretical prediction of the Stribeck-type behavior. Various loads and oil temperatures are considered. The comparison between the experimental results with a mixed elastohydrodynamic lubrication model for line contacts is indicative of good agreement.

The Stribeck Curve: Experimental Results and Theoretical Prediction

A review of friction predictions in gear teeth

Tribology, lubricants and lubrication engineering — a review

The reflection of ultrasound can be used to determine oil film thickness in elastohydrodynamic
lubricated (EHL) contacts if the opposing surfaces are fully separated by the liquid
layer. The proportion of the wave amplitude reflected depends on the stiffness of the liquid
layer, which is a function of its bulk modulus and thickness. However, in many practical
applications, boundary or mixed film lubrication is a common occurrence as the
nominal thickness of the separating film is of a similar order to the height of the surface
asperities. The reflection is then dependent on both the liquid contact and solid contact
parts and the total interfacial stiffness is the controlling parameter. In this paper an
investigation was carried to study the reflection of ultrasonic waves from the lubricated
contact between a sliding steel ball and a flat steel disc when substantial solid contact
occurs. To interpret the ultrasonic reflection results, a mixed regime model for a circular
point contact was established. The liquid film stiffness was calculated by using a predicted
film thickness and a bulk modulus estimated from published rheological models of
lubricants under high pressure. Solid contact stiffness was predicted using a statistical
rough surface contact model. Under all operating conditions, the prediction of fluid stiffness
was found to be much greater than the solid contact stiffness. The total stiffness predicted
by the model showed good agreement with experimental measurements for
kinematic cases. The model was used to separate the stiffness contributions from the asperity
contact part and lubricant layer part from the experimental data. For contact pressures
ranging from 0.42 to 0.84 GPa and sliding speed from zero to 2 m=s, the film
thickness was found to vary from 0.01 to 0.8 lm, and the proportion of the load supported
by asperity contact varied from 50% to 0%.

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Ultrasonic Measurement for Film Thickness and Solid Contact in Elastohydrodynamic Lubrication

This paper presents a mixed lubrication model for cold rolling of metals. It considers both hydrodynamic lubrication and asperity contact between the roll and the metal. The calculated results show the essential characteristics of friction and the pressure distribution in the roll bite, which indicate that a constant coefficient of friction is a poor assumption. A weighting factor for the contribution of asperity contact is obtained, and the Hitchcock formula is found adequate for representing roll deformation in calculating the inlet lubricant film thickness. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASNE Lubrication Conference held in Miami Beach, Florida, October 21–23, 1975

A Mixed Lubrication Model for Cold Rolling of Metals

This paper presents a model for mixed lubrication. The surface asperities are represented by short plasto-elastic cylinders with spherical tops. The heights of these cylinders are assumed to have a Gaussian distribution. By combining the solution of the Reynolds equation and the solution from boundary lubrication theory or the microelastohydrodynamic lubrication theory, the load and friction of the lubricated contact can be calculated. Three calculated examples which showed the essential characters and interesting results of mixed lubrication were given. The correlation with others' experimental results was reasonably good.

Yuh-Hwang Tsao

Papers

A Model for Mixed Lubrication