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2 Central European Journal of Energetic Materials

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Influence of the Shape of an Explosive Charge: Quantification of the Modification of the Pressure Field

Simoens B., Lefebvre M.

Central European Journal of Energetic Materials

2015

Vol. 12, no. 2

195--213

Many scientific articles dealing with the detonation of explosive charges and their effects suppose that the charge is spherical and centrally initiated. Yet, when discussing the blast wave effect, the charge shape and the location of initiation could be as important as the composition or the mass of the considered explosive. Specifically, close to the charge, the shape may cause significant modifications of the pressure field compared to the predictions developed for spherical charges. Experiments have been carried out, using an emulsion explosive, TNT and C4, in order to quantify the shape effect. Unconfined, centrally initiated spherical and cylindrical charges with different length-to-diameter (L/D) ratios have been fired. The pressure in the median plane was recorded for different reduced distances. Results for spherical charges showed excellent agreement with well-known references. The expected change of the pressure field in the median plane of a cylindrical charge was observed, directly linked to the L/D ratio. Peak overpressure magnifications of up to almost 3 have been measured. The dimensions of the zone within which an increase of the blast wave effect is observed, have also been determined. A similar behaviour for TNT and C4 has been demonstrated; but a different behaviour has been observed for the emulsion explosive.

Infuence of Different Parameters on the TNT-Equivalent of an Explosion

Simoens B., Lefebvre M. H., Minami F.

Central European Journal of Energetic Materials

2011

Vol. 8, nr 1

53-67

Emulsion explosives are used in a wide range of applications, amongst which some in closed vessels, where the properties at short range need to be known. A series of tests with spherical charges has been carried out to determine the TNT-equivalent at short range of an explosive emulsion based on both peak overpressure and impulse. Generally, the value is found to be constant over the considered range, with a value of 1 for overpressure and of 0.7 for impulse. In most common applications, explosive charges are not spherical. Experiments with cylindrical charges have been performed to study the infuence of (1) the shape of the charge (length-to-diameter ratio) and (2) the location of initiation (central or at one end). At the considered range, increasing L/D increases the peak overpressure and the impulse perpendicular to the axis, but decreases these effects on the axis. The central initiation causes the largest effects on the centreline. The initiation at one end causes a shift in the location of the peak overpressure, but the highest impulse remains on the centreline.