Transverse irregularities in the core of wire electrically exploded in air

The formation of the cores breaks during wire fast explosion has been studied experimentally. A series of shots (wire explosions) was performed with 25-μm and 50-μm diameter copper, nickel, and tungsten wires by using current pulse of up to 10 kA short-circuit peak and about 400 ns rise time. The velocity of propagation of the shock wave front and the velocity of expansion of the core were estimated by processing laser shadowgraphs taken at a probe radiation wavelength of 532 nm. It was shown that the breaks appeared at the sites where the wire initially had defects related to the irregularity of the crystal structure (bends, residual tensile strains, etc.) responsible for an increase in deposited energy in the respective regions. The difference between the energy deposited in the wire material at the site of a break and the energy deposition averaged over the wire length was estimated. It has also been found that large contaminants present on the wire surface can reduce the energy deposited into the wire at the resistive stage, resulting in an appreciable narrowing of the core around the contaminated region.