Effect of the degree of dispersion on the detonation wave structure in pressed TNETB

Abstract

A VISAR interferometer was used to study the reaction zone in steady-state detonation waves in pressed TNETB at different initial densities (1.23-1.71 g/cm 3 ) and degrees of dispersion (5 and 80 µm) of the initial powdered high explosive (HE). The initial density range in which a pressure rise was observed instead of the theoretically predicted chemical spike is shown to depend on the degree of dispersion of the HE. The unusual change in the parameters in the reaction zone is explained by the heterogeneous structure of pressed HEs, whose decomposition has a local nature and proceeds partially at the compression wave front. A technique for recording wave profiles using LiF windows was developed, which confirmed that all qualitative features observed when using aluminum foils ≈200 µm thick and a water window reliably reflect the detonation wave structure.Key words: pressed explosive TNETB, density, degree of dispersion, detonation wave structure, reaction zone without a chemical spike, VISAR laser interferometer, LiF window.The decomposition kinetics of pressed high explosives (HEs) in detonation is determined by the heterogeneous structure of the charges. Changes in the degree of dispersion, pressing conditions, and other factors leading to changes in the concentration and size distributions of the potential reaction centers can lead to a sudden change in the macrokinetics and qualitative changes in the reaction zone structure [1]. This is obvious if one takes into account that detonation processes are usually considered theoretically for a homogeneous medium whereas in experiments mean parameters are recorded. In this approach, the Mach front width is finite and is determined by the same heterogeneities as hot spots, i.e., the processes in the front determine the initial reaction rate and the amount of HE that reacted at these hot spots during compression. The classical Zel'dovich-Neumann-Döring (ZND) detonation theory [2] eliminates HE decomposition at the front but, nevertheless, it is frequently suitable for a

Electrical conductivity distributions in detonating low-density explosives – Grain size effect

“…Unfortunately, at low densities, fluctuations complicate the laser interferometry at the interface [12]. The method [15] using thick foils which provide averaging of the signal demonstrated peculiarities of grain size effect in some way similar to that seen in the present work. New approaches like dynamic X-ray measurements that use a synchrotron radiation source [16] as well as protonography [17], both employing natural averaging along the ray direction, could provide important information if their resolution were improved.…”

Shock Initiation and Detonation Parameters of Hexanitrohexaazaisowurtzitane (CL‐20)

“…The designations of the profiles in Figures 2 and 3 correspond to the experiment numbers in Table 1. The obtained velocity profiles for CL-20 are qualitatively similar to those previously observed in pressed RDX, HMX and other explosives, e. g. [18,[28][29][30][31][32][33]. As an example, Figure 2 shows the dependence of velocity on time for PETN, obtained under the similar experimental conditions [30].…”

“…Nevertheless, based on the obtained particle velocity profiles, it is concluded that this time is about 50 ns at the CL-20 initial density of 1.98 g/cm 3 . Similar values of reaction time are observed for many other pressed explosives [29,31,42], including CL-20based explosive containing 96 % CL-20, for which this time is equal to 48 ns [18]. In this respect, CL-20 does not exhibit any features that could be caused by high pressure at the CJ point.…”

Steady-State Detonation Wave Parameters in a FEFO/Nitrobenzene Solution

“…It is due to the fact that in 0.1 msec after the arrival of the shock wave at the foil-water interface, the decrease in the velocity related to the presence of a chemical spike in the explosive is replaced by its sharp increase due to the arrival of the compression wave rereflected from the explosive-foil interface. All details of the flow associated with circulation of waves in the foil can be analyzed in detail in the pressure-particle velocity plane (see [4]). In this case, it is important to note that in the experiment using a 400-μm thick foil, velocity oscillations disappear and the resulting dependence becomes smooth.…”