MODELING OF THIN-FILM LUBRICATION

A theological model is proposed which ran be applied to boundary lubri cation. The model satisfies the formal continuum mechanics considerati ons of material objectivity, i.e., it is indifferent to changes in coo rdinate system and reference frame. The model is applicable to thin fi lms in, which the molecular length scab is the same order as the film thickness, due to the use of ensemble, rather than spatial, averaging. The microstructure is described through the use of a director, a unit vector aligned with the molecular orientation. The model contains thr ee material parameters, i.e., the conventional viscosity, a director v iscosity which describes varying flow resistance depending on the dire ctor orientation, and an elastic modulus relating to moments required to change the director orientation. Typically, the directors are ancho red to tire boundary surfaces in a favored direction. Calculations are performed for mass velocity, director orientation, and stress in a co ntact. The lubricant exhibits nearly solid-like behavior near the surf aces, and nearly all sliding takes place across a thin shear layer. Pr edictions of friction and load are made.