Thermal Contact Resistance of Non-Conforming Rough Surfaces Part 1: Contact Mechanics Model

Abstract

A new analytical model for spherical rough contacts, in the form of a set of relationships, is developed and solved numerically. It is shown that the maximum contact pressure is the parameter that specifies the contact pressure distribution. Simple correlations for calculating the maximum contact pressure and the radius of the macrocontact area as functions of the nondimensional parameters are proposed. A relationship for pressure distributions is derived where the load is higher than the critical load. A general pressure distribution is developed that covers the entire range of spherical contacts from the smooth Hertzian to the conforming rough contact. Finally, a criterion is derived to identify flat surfaces where the surface curvature has negligible effect on the contact pressure.

Thermal Joint Resistances of Nonconforming Rough Surfaces with Gas-Filled Gaps

“…Bahrami et al 2 studied mechanical contact of nonconforming rough surfaces. A closed set of governing relationships was reported for spherical rough contacts and solved numerically.…”

“…Bahrami et al 2 proposed a general contact pressure distribution that covers the complete range of spherical rough contacts including the Hertzian smooth limit. Simple correlations were developed for the maximum contact pressure P 0 and radius of the macrocontact a L .…”

“…The governing relationships and the numerical algorithm to calculate Y (r ) were explained by Bahrami et al 2 To avoid a numerical solution, an approximate expression for the nondimensional separation is developed by using the general pressure distribution correlation.…”

Thermal Contact Resistance of Nonconforming Rough Surfaces, Part 2: Thermal Model

“…As discussed by Bahrami et al, 4 the contact between two Gaussian rough surfaces can be approximated by the contact between a single Gaussian surface, having the effective surface characteristics, placed in contact with a perfectly smooth surface. The contact of two spheres can be replaced by a flat in contact with a sphere incorporating an effective radius of curvature, 11 effective surface roughness, and surface slope as given by Figure 3 summarizes the geometrical procedure, which has been widely used for modeling the actual contact between nonconforming rough bodies.…”

“…A mechanical model was developed and presented in Part 1 of this study. 4 The mechanical analysis determines the macrocontact radius and the effective pressure distribution for the largescale contact problem, and the microcontact analysis gives the local separation between the mean planes of the contacting bodies, the local mean size and the number of microcontacts. The results of the mechanical analysis are used in the thermal analysis to calculate the microscopic and macroscopic thermal constriction resistances.…”