Theoretical and Experimental Study on Electrical Contact Resistance of Metal Bolt Joints

As a kind of fixed connection, bolt joints are widely used in engineering. In this paper, the analytic equations of the contact resistance under different situations are deduced by approximating the Gaussian distribution and the asperity deformation process based on the Greenwood-Williamson model. The equations explicitly describe the theoretical dependences of contact resistance on mechanical and electrical parameters of materials, surface topographic features, and the property of the surface oxidation film. The characteristic curves of contact resistance versus contact pressure for brass, copper, and their silver-coated counterparts are measured by using a specially designed bolted-joints structure. The experimental results are consistent with the theoretical model, indicating that, in the log-log plot, the contact resistance depends linearly on contact pressure with a slope ranging from -0.5 to -1. The analytic equations and experimental observations of contact resistance revealed in this paper can be used as a guidance for electrical contact engineering.