Detonation waves in pentaerythritol tetranitrate

Abstract

Fabry–Perot laser interferometry was used to obtain nanosecond time resolved particle velocity histories of the free surfaces of tantalum discs accelerated by detonating pentaerythritol tetranitrate (PETN) charges and of the interfaces between PETN detonation products and lithium fluoride crystals. The experimental records were compared to particle velocity histories calculated using very finely zoned meshes of the exact dimensions with the DYNA2D hydrodynamic code. The duration of the PETN detonation reaction zone was demonstrated to be less than the 5 ns initial resolution of the Fabry–Perot technique, because the experimental records were accurately calculated using an instantaneous chemical reaction, the Chapman–Jouguet (C-J) model of detonation, and the reaction product Jones–Wilkins–Lee (JWL) equation of state for PETN detonation products previously determined by supracompression (overdriven detonation) studies. Some of the PETN charges were pressed to densities approaching the crystal density and exhibited the phenomenon of superdetonation. An ignition and growth Zeldovich–von Neumann–Doring (ZND) reactive flow model was developed to explain these experimental records and the results of previous PETN shock initiation experiments on single crystals of PETN. Good agreement was obtained for the induction time delays preceding chemical reaction, the run distances at which the initial shock waves were overtaken by the detonation waves in the compressed PETN, and the measured particle velocity histories produced by the overdriven detonation waves before they could relax to steady state C-J velocity and pressure.

Ignition and growth modeling of detonation reaction zone experiments on single crystals of PETN and HMX

“…Fedorov et al [6] inferred reaction times of 90 -95 ns in seven experiments. Figure 4 shows the calculated PETN/LiF particle velocity histories for a PETN single crystal and a pressed PETN charge [5]. The initial interface [6].…”

“…The reacting "hot spots" rapidly grow consuming the neighboring explosive particles and increasing the pressure and temperature as C-J detonation is approached [4]. "Super" detonation is not observed in porous solids, unless the initial density is extremely close to TMD [5]. Recently, Fedorov et al [6] reported nanosecond time resolved measurements of the interface particle velocity histories of detonating PETN and HMX single crystals with LiF windows.…”

“…The unreacted JWL EOS's for PETN and HMX are fitted to the von Neumann spikes measured by Fedorov et al [6]. The reaction product JWL EOS's are based on those for pressed HMX PBX's [8] and PETN explosives [5], using measured detonation velocities and calculated C-J pressures. Table 1 lists the I&G model parameters for a PETN single crystal, while Table 2 lists those for an HMX single crystal.…”

Hotspots from atomistic simulation to mesoscopic hydrodynamics modeling

“…The challenge is to compare microscopic simulation with experiment and coupling of simulation as well with recent results [3]. Different macroscopic kinetics and hotspot models are calibrated by experimental data and more precise simulations at microscopic to represent a pop-plot data [4,5] or initiation thresholds of shock-induced chemistry [6]. However, there is still a great debate of direct hotspot simulation.…”

Detonation wave profiles in HMX based explosives

“…Laser light reflected from the mirror is Doppler shifted when the velocity changes and an interferometer transduces this into particle velocity of the interface vs. time. Several studies have used this technique in various interferometer setups (ORVIS and Fabry-Perot) to estimate reaction zones in various explosives (3)(4)(5). Time resolution can range from 10 ns down to subnanosecond, depending on the interferometer and the recording technique.…”