Expansion of superheated metals

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Abstract
The short interval of an exploding-wire expansion characterized by rapid rise of resistance, voltage, and electrically deposited energy is studied using time-correlated image-converter photographs, x-ray shadowgraphs, and electrical measurements from identical explosions. Striations in density of the molten expanding core appear concurrently with the electrical signature of the vaporization expansion wave and shortly before billows appear on the boundary surface of the expanding vapor cloud. Even though resolution and penetration do not allow correlation between individual striations and billows, this concurrence suggests that striations are a product of the vaporization process. Arguments are given to show that skin effect and pinch effect do not initiate striation. The same cannot yet be said of Joule heating dependent on the inverse fourth power of radius. Thus striation spacing may reflect underlying departures from uniformity in radius or in microcrystalline structure of the wire.