This abstract was not submitted electronically.
[F1.02] Modeling the detonation structure of heterogeneous explosives
Jean-Philippe Dionne, John H.S. Lee (McGill University)
Modeling the detonation structure of condensed explosives requires the use of equations of state (EOS) and chemical rate laws adapted to the presence of condensed matter in the reaction zone. Equations of state for the unreacted explosive and for the detonation products are needed. Chemical rate laws with constants fitted to experiments have been included successfully in models dealing with homogeneous explosives. However, commercial explosives often include heterogeneities such as solid particles. The behavior of these particles under shock compression has to be known. Simple mixing rule can be used to obtain a global equation of state for the heterogeneous mixture once an equation of state is selected for each phase. The solid particles are also the locus of very high local temperature where chemical reactions are triggered. This triggering mechanism, typical of heterogeneous explosives, greatly affects the detonation propagation limits. In the present work, the use of realistic equations of state and chemical rate laws in the detonation structure calculations for heterogeneous explosives has been investigated.
[F1.03] A Closed Water-Filled Cylinder for Characterizing Non-Ideal Explosives
Raafat Guirguis, Reid McKeown, John Kelley (Naval Surface Warfare Center, Indian Head, MD 20640-5035)
Non-ideal explosives containing a significant fraction of slow-reacting components, such as underwater explosives, pose a challenge for conventional testing methods. In contrast to ideal explosives in which a 1" cylinder test is usually adequate, 4" and 8" cylinder tests are often required for underwater explosives in order to allow the slow reacting components enough time to participate. A closed version of the Guirguis Hydro-Bulged Cylinder test is described in this paper as an alternative. In this test, a small quantity of the explosive is suspended at the center of a thin-walled small-scale aluminum cylinder completely filled with water under slight overpressure. The ends of the cylinder are closed using thick aluminum plugs. The wall expansion due to explosion of the charge is measured in real-time using a Streak Camera while the pressure at the interface between the cover and the water is measured using a piezo-electric transducer. In the paper, numerical simulations are used to predict the time-evolution of the wall expansion and pressure at several locations due to detonation of both ideal and non-ideal small explosive charges.
[F1.04] Detonation in An Aluminized Explosive and Its Modeling
J. Lee, J.H. Kuk, S-y. Song, K.Y. Choi, J.W. Lee (Agency for Defense Development, Taejon, Korea)
Detonation properties of an aluminized explosive cannot be described by a simple theory, such as the Chapman-Jouguet theory, which assumes energy release to be instantaneous. Aluminum reacts very slowly, and, thus, the energy released from the aluminum reaction does not contribute much to the leading shock wave. As a result, detonation velocity and pressure of an aluminized explosive are much lower, but detonation wave duration is much longer, than those expected only based on its energy content. This is why aluminized explosives are preferred to conventional high explosives for blast-type applications.
We calibrated a reaction-rate equation for an heavily aluminized
explosive from two-dimensional steady-state experiments by applying
the detonation shock dynamics. To verify short- and long-term
behavior of the rate equation, we numerically modeled a
detonation-wave profile of a cylindrical charge, and underwater
explosion properties. The calculated results agreed with the
experimental observations very well. Using the rate equation, we
were able to predict most detonation properties.
[F1.05] Shock Hugoniot Behavior of Mixed Phases with Widely Varying Shock Impedances
John Reaugh, Edward Lee (Lawrence Livermore National Laboratory)
The shock velocity dependence on shock pressure in composite explosive materials containing polymeric materials is known to exhibit marked non-linear behavior in the Us - up plane at low pressures. This is in addition to the non-linear behavior noted in pure polymeric materials. The precise description of this behavior is important in analyzing the response of energetic materials to impact shocks.
We will show that the mismatch of the shock impedances in such materials as rocket propellants composed of polymer binder, aluminum, and ammonium perchlorate can be expected to exhibit a very large initial slope of the shock velocity, Us, dependence on the particle velocity, up. This slope is simply a result of the equilibration of Hugoniot pressure amongst the phases. With accurate descriptions for the equations of state of the individual components, we successfully predict the extreme slope at low compression. The effect is primarily due to the very large compression of the polymeric phase at relatively low volumetric compression of the whole mixture. Examples are shown and compared with available experimental results.
[F1.06] Blast Waves From Non-ideal Explosives
Van D. Romero, Pharis E. Williams (Energetic Materials Research and Testing Center, New Mexico Tech, Socorro, NM)
The non-ideal behavior of explosives comes from different ways which retard the energy release from the explosive. These include a lack of oxygen balance which results in energy being released after the shock wave from the detonation has gone into the surrounding air and the detonation products react with this fresh source of oxygen as it is included within the shock wave. Also included are slow and/or multiple reactions which cause energy to be released late in the reaction zone of the detonation when the pressure of the detonations has dropped until the local sound speed has fallen below the detonation velocity. All energy released after this point cannot keep up with the detonation shock wave and must wait to catch up with the blast wave that propagates into the air. Both of these non-ideal characteristics of the explosive reduce the irreversible losses to the air close to the explosive charge by reducing the peak pressure, and therefore, the temperature compressive heating of the air. Less irreversible losses to the air means more energy propagates to greater distance. This presentation covers the research conducted into the influence of these non-ideal effects upon the propagation of peak pressures and the positive and negative impulses from non-ideal explosives.