THE FRAGMENTATION OF WIRES CARRYING ELECTRIC-CURRENT

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 stat e without signs of significant melting. The experiments show that the wires break in tension due to some longitudinal force, the nature of t his force being unknown. Simple estimates made in the past by other au thors showed that neither the pinching effect nor thermal expansion wa s responsible for the disintegration of the wire, since the tension pr oduced was too low to extrude the wires. A search for a longitudinal f orce 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, w hen the current increases from zero to a constant value in a step-func tion manner. Two main aspects are studied, namely (i) the possible amp lification of stress waves induced by the electromagnetic pinch force and (ii) the dynamic stress induced by the thermal expansion. It is sh own that, for wires with free ends, the magnitude of tensile stress pr oduced by the thermal expansion may well exceed the ultimate strength of the material.