Evaluation of the X-Ray CT Visualisation Technique for Characterising Electrical Contacts

Real surfaces consist of a roughness on the microscopic scale, which influences mechanical contact when two surfaces are brought together. Mechanical contact only occurs in a specific number of areas on the apparent area of contact. This has been visualised by Thomas and Probert by revealing imprints in smooth steel optical flats. These flats were dismantled after being in contact with sand-blasted steel surfaces with contact normal forces between 5 and 100 kN. McBride has visualised mechanical areas of contact through a glass slide which was in contact with a silver hemispherical surface for contact normal forces between 0.01 and 1 N. Lalechos and Swingler have presented a technique for visualising a real electrical contact interface without the need to dismantle the component parts. The technique utilises the X-ray computer assisted tomography method to produce “contact maps” of portions of areas of contact at the electrical contact interface.

This paper presents work evaluating the credibility of this new technique for characterising the contact interface. The first part of the work focuses on comparing values for the mechanical area of contact, Am, as determined by the new technique to several theoretical methods of determining Am.

The second part of this work compares the new technique with the 3D profiling technique of McBride.