An Instability for Parallel Sliding of Solid Surfaces Separated by a Viscous Liquid Film

Abstract

Thermoelastic phenomena in lubricated face type seals are analyzed for possible instabilities which may lead to large surface deformations and seal failure. Thresholds of such instabilities are found where a small, steadily moving, surface disturbance will neither grow nor decay. For a good thermal conductor sliding on a good insulator, several such thresholds exist. Only one, however, falls within a reasonable operating range, the critical sliding speed being Ucrit=hκ¯KMμαM where h¯ is the nominal film-thickness, κ the wave number of the disturbance, KM the thermal conductivity of the conductor and αM its coefficient of thermal expansion, and μ the viscosity of the oil. Expressions are given for the approximate limits of h¯ within which such a threshold lies. Finally, it is shown that, as expected, a disturbance will grow when U > Ucrit and decay when U < Ucrit.