On relations between geometries of microcontact clusters and their overall properties

Interaction between contacts in a cluster produces major effect on compliance of an interface between contacting surfaces and its thermal/electrical resistance. Several methods have been developed to account for this effect. Probably the easiest one [J.A. Greenwood, Constriction resistance and the real area of contact, Br. J. Appl. Phys. 17 (1966) 1621–1622] operates with Holm’s radius – microstructural parameter having the dimension of length. Being introduced in the context of electrical conductance, this parameter may be used in the compliance problem as well due to cross-property connection between the two properties. The present paper focuses on relating Holm’s radius to cluster geometry. Explicit formulas are derived and illustrated on several examples. The obtained results allow one to estimate the effect of interaction between individual contact spots directly from the cluster image.