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International Journal of Fluid Mechanics Research
ESCI SJR: 0.206 SNIP: 0.446 CiteScore™: 0.5

ISSN Print: 2152-5102
ISSN Online: 2152-5110

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International Journal of Fluid Mechanics Research

DOI: 10.1615/InterJFluidMechRes.v30.i5.70
16 pages

Model of Elastohydrodynamic Lubrication with Molecularly Thin Lubricating Films. Part I: Development of Analysis

Yongbin Zhang
Zhejiang Jinlei Electronic and Mechanical Co. Ltd.
Keping Tang
Hangzhou Gear Box Company, Zhejiang Province, P. R. of China
Guoshen Lu
Zhejiang Beijing Orient Vacuum Electronic Co., Ltd, Zhejiang Province, P. R. of China


This paper develops an analysis for study of hydrodynamic lubrication in smooth line contacts at isothermal and steady state conditions where molecularly thin lubricating films occur, taking into account the elastic deformation of the contact surfaces. Considering the lubricant's rheology within molecularly thin film of a lubricant measured by recent experiments [1], the Reynolds equation in the present study is based on the non-Newtonian viscoplastic lubricant rheological model by Zhang and Lu [2], incorporating the lubricant's viscosity, the shear modulus of elasticity, shear strength, contact-lubricant interfacial shear strength, and Eyring stress of the lubricant. The mentioned model is valid not only for thick lubricant films, but also can be extended to molecularly thin lubricant films, for which the parameters characterizing the lubricant's property are respectively expressed as functions of the pressure and the thickness of the lubricant film. It can be used for wide operational scopes where shear thinning, slip and elastic behavior effects of the lubricant may occur significant. These effects may be important in hydrodynamic lubrication where the lubricant film is molecularly thin. A hydrodynamic pressure is derived from the Reynolds equation. The effect of the flow factor proposed by Zhang and Tang [13], which occurs due to inhomogeneity and discontinuity of the lubricant across its film thickness for molecularly thin film lubrication, is incorporated in the present study. The effect of the surface pressure (i. e., Van der Waals and solvation pressures) is also considered. These last influence carried load of the contact and the lubricant film thickness, respectively, by acting on the contact surfaces and changing the elastic deformation of the contact surfaces. The total pressure in the contact is obtained by summation of hydrodynamic and the surface pressures.