The shock initiation threshold of PBX‐9404 has been studied over the pressure range 3.1 GPa‐28 GPa with pulse lengths ranging from 0.007 μs‐0.63 μs. The short‐duration, high pressure pulses were produced by the impact of thin plastic flyer plates accelerated by electrically exploded metal foils. We performed the experiments on explosive pellets 25.4 mm in diameter with thicknesses of 6.0 mm, 10.1 mm and 19.1 mm. No dependence of the initiation threshold on pellet thickness was observed. The data are represented reasonably well by either the critical initiation energy or by the constant P2τ initiation criteria.
We describe new techniques that permit the use of low-impedance manganin stress gauges in chemically reacting shock waves in the 1.0–40.0 GPa range. The rugged, small, and fast response gauge has reproducibility better than 2% when used in conjunction with a pulsed bridge circuit and adjustable, current-regulated power supplies. Techniques are presented for fabricating the transducer package, calibrating the bridge circuit and oscilloscopes, designing the drive system, and reducing the data. Data are presented for planar impact experiments performed with a 102-mm gas gun on high-explosive samples. In particular, we directly measured the Chapman-Jouquet pressure in the explosive RX03-BB [92.5% triaminotrinitrobenzene (TATB)/7.5% polychlorotrifluoroethylene (Kel-F binder)] as 28.2±0.6 GPa. These new developments open the possibility of applying low-impedance manganin gauges in chemically reactive hydrodynamic flows such as the evolution of a shock wave into a detonation wave.
Articles you may be interested inSystematic uncertainties in shock-wave impedance-match analysis and the high-pressure equation of state of AlWe have developed a versatile tool for generating planar shock waves. This system, which we call the electric gun, is capable of projecting thin flyer plates with velocities in the range 1-20 km/s. It is presently being used in high-explosives-initiation experiments and is being developed for equation-of-state measurements in the 1-5 TPa range. We describe the electric gun facilities that are operational at Lawerence Livermore Laboratory and discuss applications of electric gun technology to problems of interest to shock-wave researchers.
A method is presented for computing the transient current and temperature distributions in electrically exploded foils. The model employed is applicable up until the time of burst. Calculations are presented for Al, Cu, and Au foils showing good agreement with experimental current waveforms and burst times over a wide range of capacitor-bank charging voltages and for varying foil cross sections. The two-dimensional nature of the calculation permits investigation of effects associated with nonuniform heating of the foil and gives an estimate of the simultaneity of burst.
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