SCALING UNDERWATER EXPLODING WIRES
NAVAL RESEARCH LAB WASHINGTON DC
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Five-mil Nichrome wires have been exploded under water using a 12- microfarads capacitor which stored energy up to 100 joules. The results indicate that peak pressure scales like a chemical explosive if losses due to the circuit and joule heating of the wire itself are accounted for. On this basis, the equivalent weight of TNT represented by the electrical energy stored in the capacitor is W 5250.325CV sub 0 squared--EvHd where W is the weight in micropounds, C is the capacitance in farads, V sub 0 is the initial charging voltage, Ev is the estimated energy dissipated by the wire in joules, and Hd is the heat of detonation of TNT in calories per gram. This scaling behavior extends the law of similarity six decades in terms of weight, from pounds to micropounds. The peak pressure for exploding-wire phenomena has been obtained from data and is emprically expressed as pm 26,800 cube root of WR to the 1.08 power where pm is peak pressure and R is pressure-gage distance. The instrument response to the short-duration shock wave gives rise to a new definition of the explosion constant tau sub e. The reduced time-constant parameter shows qualitative agreement in value and slope with chemical data scales, and is given empirically as tau sub ecube root of W 70cube root of WR to the minus 0.22 power.
- Ammunition and Explosives