No abstract

It is indicated that the sealing capacity depends on the contact characteristics-the relative contact area and the gap density in the joint. To determine the contact characteristics, a discrete roughness model is used in the form of a set of spherical segments, the distribution of which in height is related to the bearing curve described by the regularized beta function. The contact of a single asperity is considered with taking into account the influence of the remaining contacting asperities. The equations for determining the relative contact area and gap density in the joint depending on the dimensionless force parameters for elastic and elastic-plastic contacts are provided.

Abstract-Initially, a contact between a rigid rough surface and a homogeneous elastic half-space without taking into account the mutual influence of microasperities is considered. To determine the dependence of the density of gaps in the joint on dimensionless the force elastic geometrical parameter, the discrete roughness model presented by microasperities in the form of equal spherical segments with the height distribution corresponding to the bearing profile curve of the real surface is used. To determine the volume of intercontact space, the volumes of gaps attributable to the single contacting or noncontacting asperities are determined. In this case the equations describing the sections of surfaces of contacting or noncontacting asperities and the half-space under load are used. Then we consider a contact between a rigid rough surface and a layered half-space consisted of the coating with thickness δ1 and the substrate. By using the stiffness model of a layered half-space, the elastic characteristic are determined for every contacting asperity. The system of transcendental equations which allow to determine the dependence of the density of gaps in case of contact through coating layer on the roughness parameters, material properties, coating thickness and applied load is given. The characteristic curves showing the dependence of the density of gaps in the joint for different coating thickness are given.Keywords-rough surface, spherical asperity, elastic contact of asperities, volume of gaps, density of joint, thin-layer coatings, layered elastic half-space.

The contact of a rigid rough surface and an elastic layered half-space which consists of coating with thickness δ1 and the substrate. To determine the dependence of the relative contact area on dimensionless the force elastic geometrical parameter , the discrete roughness model presented by microasperities in the form of equal spherical segments with the height distribution corresponding to the bearing profile curve of the real surface is used. By using the stiffness model of layered half-space, the elastic characteristics for every each contacting asperity are determined. The system of transcendental equations which allow to determine the dependence of the relative contact areaη1 in case of contact through coating layer on the roughness parameters, material properties, coating thickness and applied load is given. The mutual influence of the microasperities is taken into account.

The paper indicates that the application of roughness models and the theories of contacting rough surfaces developed by Greenwood-Williamson and N.B. Demkin for solving the problems of hermetology leads to significant errors. This is explained by much greater contact pressures than for the tribology problems, by describing only the initial part of the reference surface curve, the lack of allowance for the plastic extrusion of the material. A brief review of methods for describing the introduction of a sphere into an elastoplastic reinforced half-space is given. The properties of the elastoplastic reinforced material are described by the power law of Hollomon. To describe the indentation and flattening of single spherical asperity, the results of finite element modeling are used. The cases of contacting a rigid rough surface with an elastoplastic half-space and a rigid smooth surface with a rough surface are considered. To determine the relative contact area, the discrete roughness model is used in the form of a set of spherical segments distributed along the height in accordance with the curve of the reference surface.