Abstract
Lubricated contact with nanoscale oil film is modeled for friction. Effect of the van der Waals pressure and the solvation pressure forces on such ultrathin lubricating oil film is considered while finding the friction and other parameters. Hydrodynamic action is represented using transient thermoelastohydrodynamics. Net pressure due to hydrodynamic, solvation, and van der Waals’ action is integrated over the contact area to find contact load. Conjunctional friction due to thermal activation of such ultrathin film is derived using the Eyring model. Effect of molecular dimension on friction is studied.
Highlights
Ultrathin film transition is in between mixed and boundary regimes of lubrication
In mixed regime of lubrication, the contiguous surface geometry appears in film profile, while in boundary regime a total fluid film rupture occurs and the contiguous solids remain in contact
Film thickness of 0.5 nm is measured for OMTC, nhexadecane, and n-tetradecane
Summary
In mixed regime of lubrication, the contiguous surface geometry appears in film profile, while in boundary regime a total fluid film rupture occurs and the contiguous solids remain in contact. In between these two lubrication regimes, there exists a transition, where the film is in order of 0.5 nm–5 nm and is termed as ultrathin film. The solvation pressure is calculated by solving the transformed Ornstein-Zernike equation for hard spheres in a two-phase system with Perram’s method and using the Derjaguin approximation They applied this new concept to elastohydrodynamic problems, in which the film thickness is very small and force due to solvation and van der Waals’ action is significant. Based on the literature survey, it is realized that a model of thin film lubrication will be worth presenting with the inclusion of solvation and van der Waals’ action (Figure 4)
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