Blast wave effects at short distances

The peak shock overpressures for a blast wave have been calculated by several methods, and the results have been verified by a large number of experimental measurements. The use of the standard overpressure curve, however, may lead to serious underestimation of blast wave effects at very short distances (probably at scaled distances of less than one meter). We have calculated the blast wave from a detonating sphere of explosive using the one-dimensional reactive hydrodynamics code HYDROX, and have obtained good agreement with the standard curve. To describe the interaction of the blast wave with a flat plate, the calculation was also done with the two-dimensional code 2DE (with a much coarser mesh). The air shock matches into the plate at the predicted pressure, but a second, stronger shock is then produced by the arrival of the detonation products. The strength of the second shock decays more rapidly with distance than the first (air) shock. This effect has been verified experimentally. 7 refs., 6 figs

Data Analysis, Pre-Ignition Assessment, and Post-Ignition Modeling of the Large-Scale Annular Cookoff Tests

In order to understand the implications that cookoff of plastic-bonded explosive-9501 could have on safety assessments, we analyzed the available data from the large-scale annular cookoff (LSAC) assembly series of experiments. In addition, we examined recent data regarding hypotheses about pre-ignition that may be relevant to post-ignition behavior. Based on the post-ignition data from Shot 6, which had the most complete set of data, we developed an approximate equation of state (EOS) for the gaseous products of deflagration. Implementation of this EOS into the multimaterial hydrodynamics computer program PAGOSA yielded good agreement with the inner-liner collapse sequence for Shot 6 and with other data, such as velocity interferometer system for any reflector and resistance wires. A metric to establish the degree of symmetry based on the concept of time of arrival to pin locations was used to compare numerical simulations with experimental data. Several simulations were performed to elucidate the mode of ignition in the LSAC and to determine the possible compression levels that the metal assembly could have been subjected to during post-ignition