Conditions for the Rupture of a Lubricating Film—Part II: New Boundary Conditions for Reynolds Equation

Abstract

The pressure and flow conditions upstream of the rupture point of a lubricating film are analyzed with the theoretical model derived in Part I. The boundary conditions on the pressure and pressure gradient for use with Reynolds’ equation are developed as functions of a dimensionless parameter involving viscosity, speed, and surface tension. The load-carrying capacity which results from the use of these new boundary conditions does not differ appreciably from that of other boundary conditions in current use, except when the bearing load is extremely light, or when surface tension is large compared with the product of speed and viscosity. A simple experiment was conducted using a cylindrical lens bearing on a rotating oil-lubricated glass plate. Measurements of the bearing load and the location of the film attachment to the lens were in good agreement with the theory.