Electrical conduction and Joule effect in one-dimensional chains of metallic beads: hysteresis under cycling DC currents and influence of electromagnetic pulses

The passage of an electric current through a chain of metallic beads causes a contact temperature rise and a permanent change of the contact area between beads, which in turn modify the electrical resistance of the chain. These effects are analyzed by measuring the voltage-current characteristics of a chain. These characteristics exhibit nonlinear and hysteretic behaviors. In this article, we particularly focus on the electrical behavior under cycles of increasing and decreasing current. Experimental results compare well with those of a model derived on the assumption of equilibrium between Joule heating in the contact between beads and thermal dissipation by conduction within the material. It is shown however that models based on the Wiedemann-Franz's law fail to describe the electro-thermo-mechanical behaviors of chains of beads carrying currents and submitted to a small static compression force. We finally analyze the strong modifications of the electrical behavior of a chain of beads subjected to electromagnetic perturbations produced by a spark.