COUPLING OF EXPLOSIVE ENERGY IN THREE‐DIMENSIONAL MODELS
The coupling of explosive generated P waves to the surrounding medium was investigated in a three‐dimensional laboratory model. For tightly coupled charges the amplitude was found to increase as [Formula: see text], and the pulse width as [Formula: see text], where W is the charge mass. Only a few hundredths of one percent of the energy in the explosion was transmitted in the initial P wave. When charges were fired in air‐filled cavities, the amplitude of the energy in the P wave increased to a maximum and then decreased with increasing cavity radius. The amplitudes from cavity shots were never less than the amplitudes for the tightly coupled shots. As the cavity radius increased, the pulse width of the P wave decreased to a minimum, an indication of a decrease in the size of the equivalent cavity, and then increased with further increase in cavity size. The period minimum is interpreted as corresponding to the transition from nonelastic to elastic response of the cavity wall. The cavity pressure at this transition is about one‐half the nominal tensile strength of the material. Scaling to the Sterling nuclear event is examined, and the conclusion is that the disagreement between field tests of decoupling and our experiments is due to the dominance of short period energy in our experiments. The results cast doubt on the general validity of partial decoupling.