Micro-elastohydrodynamic lubricant film formation in rotary lip seal contacts

In this paper solution is given to the lubricant fluid film developed under rotary lip seals. The study is carried out considering the less favourable hypothesis of a sealing junction formed by two parallel sliding surfaces. A mathematical model is developed which treats the hydrodynamic pressure required for the generation of a lubricant film as a combination of two separate components. Firstly, the Micro–EHD action originated by the asperities’ summits in virtual contact is analysed; secondly, the hydrodynamic pressure generated by the wavy morphology at the sealing interface is studied. The Micro–EHD fluid film developed between colliding asperities is evaluated using up-to-date forms of fluid film calculation of elliptical contacts under isoviscous elastic lubrication conditions. The real area of contact and real pressure originated between the two rough surfaces in match is solved by applying a generalised form of the Greenwood-Tripp stochastic model for contact of two rough surfaces. Results of parametric computations using present algorithms indicate the bounds of validity of the developed theory and its performances when compared with asperity based models for rotary seal lubrication.

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