Influence of Asperity Deformation Mode on Gas Leakage between Contacting Surfaces

Abstract

The gas flow between two surfaces in contact is affected by the way in which the surface asperities are deformed by the contact load. The plastic deformation of wedge-shaped model asperities, supported on rigid bases, is examined. Full account is taken of the effect of displaced material on the deformation pressure and on the rate of fluid leakage between the contacting surfaces. Characteristics of deformation pressure versus compression are plotted for a range of wedge asperity angles, assuming two-dimensional deformation and non-hardening material, and from these are derived expressions for fluid leakage between the contacting surfaces. It is shown that a critical contact pressure exists for a given seal contact load at which the leakage rate has a maximum value. This contact pressure may be avoided by either increasing or decreasing the seal length.