The fragmentation of wires carrying electric current

Abstract

Exploding wires are widely used in pulsed power systems. However, many aspects of the wire explosion remain unclear. If the electric current density is not too high, the wires may disintegrate in the solid state without signs of significant melting. The experiments show that the wires break in tension due to some longitudinal force, the nature of this force being unknown. Simple estimates made in the past by other authors showed that neither the pinching effect nor thermal expansion was responsible for the disintegration of the wire, since the tension produced was too low to extrude the wires. A search for a longitudinal force had even led to a certain controversy in electrodynamics. In this investigation we employ the equations of magneto-thermo-elasticity to study stress waves induced in metal wires by a high pulsed current, when the current increases from zero to a constant value in a step-function manner. Two main aspects are studied, namely (i) the possible amplification of stress waves induced by the electromagnetic pinch force and (ii) the dynamic stress induced by the thermal expansion. It is shown that, for wires with free ends, the magnitude of tensile stress produced by the thermal expansion may well exceed the ultimate strength of the material.