Abstract
Experimental results have confirmed that parallel rough surfaces can be separated by a full fluid film. However, such a lift-off effect is not expected by the traditional Reynolds theory. This paper proposes a deterministic mixed lubrication model to understand the mechanism of the lift-off effect. The proposed model considered the interaction between asperities and the micro-elastohydrodynamic lubrication (micro-EHL) at asperities within parallel rough surfaces for the first time. The proposed model is verified by predicting the measured Stribeck curve taken from literature and experiments conducted in this work. The simulation results highlight that the micro-EHL effect at the asperity scale is critical in building load-carrying capacity between parallel rough surfaces. Finally, the drawbacks of the proposed model are addressed and the directions of future research are pointed out.
Highlights
The Reynolds equation has been widely used to predict the pressure distribution built up between two mating surfaces experiencing relative motion since 1886 [1]
Based on the mixed elastohydrodynamic lubrication (EHL) model reported by Zhu and Hu [40,41], a deterministic mixed lubrication model for parallel surfaces is proposed, with its basic equations and main features addressed
Numerical procedures previously developed for mixed EHL were improved to be compatible with parallel rough surfaces
Summary
The Reynolds equation has been widely used to predict the pressure distribution built up between two mating surfaces experiencing relative motion since 1886 [1]. According to the Reynolds equation, two parallel surfaces cannot generate pressure except in a squeeze motion. Experimental studies have continuously shown that considerable pressure can be generated between parallel rough surfaces. Fogg [2] tested thrust bearings with parallel surfaces. Results showed considerable evidence, such as low friction losses and absence of wear scars on the surfaces, which indicated that the thrust bearing worked in the full film regime. Lebeck [3] reviewed a series of experimental results of parallel sliding surfaces, including seals and bearings. As the speed was increased, the bearing surface was lifted, and the asperity contact and friction were reduced. Ayadi and Brunetière et al [4]
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