An original inverse method to determine the approximate electrical contact area between a clip and a bar

The determination of the electrical contact area between two contact members is a recurrent problem which will probably never be solved exactly. In this paper, we present an original method which allows us to determine the approximate electrical contact area obtained when a branch of an elastic clip is pressed against a flat bar. This method is based on the measurement of the electric potential on the bar, on a U shaped contour located as close as possible to the clip. In the experimental set up, the contour potential V/sub m/(s) is quickly recorded, while the contact is fed by a stabilized current of /spl plusmn/30 A, to rule out thermal drifts and EMFs. The electrical potential is measured between the top of the clip and a metallic probe sliding on the contour, with a constant contact force. Assuming that the contact area is elliptic, the unknown parameters of the problem are the location of the ellipse and its main dimensions. The program used to determine these parameters couples a 2D finite element module with an optimization module of the MATLAB/sup (R)/ software. The algorithm starts with an arbitrary set of values for the parameters, uses the experimental boundary conditions and calculates the potential differences V/sub m/(s) corresponding to the experimental contour. Then the coupled "optimization module and FEM module" runs, changing the parameters, in order to make V/sub c/(s) as close as possible to V/sub m/(s). The various tests results of the methodology are very satisfactory.