Physical Origin of Hot Spots in Pressed Explosive Compositions

Belmas, R.; Plotard, J. P.

doi:10.1051/jp4:1995406

Cited by 15 publications

(9 citation statements)

References 8 publications

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“…But, for an impact velocity of 798 m/s, i-e a shock stress input of 4.5 GPa, only a few amount of T2 is transformed into decomposition products. These results confirm thatT2 can then be consider as inert below 4 GPa as previously indicated (4). Figure 1-(b) shows a 13.6 GPa shock stress input produced in a 25 mm thick T2 sample by a 10 mm Alumina flyer at a velocity of 1786 m/s (12).…”

Section: Results For Single and Double Shock Wavessupporting

confidence: 70%

Development of a reactive burn model based on an explicit viscoplastic pore collapse model

Bouton¹,

Lefrançois²,

Belmas³

2017

AIP Conference Proceedings

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Abstract. The aim of this study is to develop a reactive burn model based upon a microscopic hot spot model to compute the shock-initiation of pressed TATB high explosives. Such a model has been implemented in a lagrangian hydrodynamic code. In our calculations, 8 pore radii, ranging from 40 nm to 0.63 m, have been taken into account and the porosity fraction associated to each void radius has been deduced from the Ultra-Small-Angle X-ray Scattering measurements (USAXS) for PBX-9502. The last parameter of our model is a burn rate that depends on three variables. The first two are the reaction progress variable and the lead shock pressure, the last one is the chemical reaction site number produced in the flow and calculated by the microscopic model. This burn rate has been calibrated by fitting pressure, velocity profiles and run distances to detonation. As the computed results are in close agreement with the measured ones, this model is able to perform a wide variety of numerical simulations including single, double shock waves and the desensitization phenomenon.

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Section: Results For Single and Double Shock Wavessupporting

confidence: 70%

Development of a reactive burn model based on an explicit viscoplastic pore collapse model

Bouton¹,

Lefrançois²,

Belmas³

2017

AIP Conference Proceedings

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“…In the viscous flow state, the binder loses more adhesion to explosive particles and the compression strength of PBX decreased significantly. Experimental results [32,35,36,37] of PBX compression strength are shown in Figure 4 for comparison. Different experimental data come from either different techniques or different temperatures.…”

Section: Resultsmentioning

confidence: 99%

“…Compression strength curve of PBX at different temperatures, also shown are experimental results from references [32,35,36,37]. …”

Section: Figurementioning

confidence: 97%

Mesoscale Simulation to Study Constitutive Properties of TATB/F2314 PBX

Zhang

Sang

et al. 2019

Materials

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Material Point Method (MPM) mesoscale simulation was used to study the constitutive relation of a polymer bonded explosive (PBX) consisting of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and a fluorine polymer binder F2314. The stress-strain variations of the PBX were calculated for different temperatures and different porosities, and the results were found to be consistent with experimental observations. The stress-strain relations at different temperatures were used to develop the constitutive equation of the PBX by using numerical data fitting. Stress-strain data for different porosities were used to establish the constitutive equation by fitting the simulation data to an improved Hashion-Shtrikman model. The equation can be used to predict the shear modulus and bulk modulus of the PBX at different densities of the sample. The constitutive equations developed for TATB/F2314 PBX by MPM mesoscale simulation are important equations for the numerical simulations of the PBX at macroscale. The method presented in this study provides an alternative approach for studying the constitutive relations of PBX.

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“…For the majority of [27], an RP-80 detonator variant used; however, an RP-1 was used for the comparison between the optical wave traveling at 5 mm/µs that appears to catch the slower density wave derived from X-rays at almost exactly the end of the pressing where the high-density output pellet sits. The new findings presented here, as well as in [17], suggest that the density discontinuity is an initially accelerating reaction wave undergoing a hot-spot-driven shock-to-detonation transition (SDT) process [29][30][31].…”

Section: Explosive Powder Studiesmentioning

confidence: 96%

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

Rae

Rettinger

2021

Shock Waves

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The particle velocity created in beds of both low-density inert sugar and explosive PETN as a function of distance from an exploding bridgewire was measured using optical velocimetry and a silvered PMMA window. As expected, more violent bridge-bursts (from a greater-stored-energy capacitive discharge unit) resulted in greater particle velocities and a better supported compaction wave in sugar. In all cases, ramp waves, not shocks, were observed in the inert sugar. Large window velocities were observed for very powerful bursts (up to 270 m/s), but bursts required for stochastic detonator operation conditions resulted in sugar/PMMA window velocities of only 8–10 m/s 0.85 mm from the bridge location. In contrast, after a distance of only 0.65 mm, a building shock wave was observed in PETN under both threshold and reliable firing conditions. Subsequently a hot-spot-driven shock-to-detonation (SDT) process was observed prior to full detonation. The measured buildup process accounts for $$\approx $$ ≈ 66% of the so-called excess transit time (ETT) between the observed and theoretical total function time for the particular exploding-bridge-wire (EBW) detonator studied. The remainder must occur in the powerful output pellet region. In contrast to a common understanding, the ETT is found to be a weak function of the discharge energy. Thus, the operation of the detonator after a bridge-burst energy-to-powder reaction transition process is found to be hot-spot-driven SDT in both the low- and high-density pellets.

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Physical Origin of Hot Spots in Pressed Explosive Compositions

Cited by 15 publications

References 8 publications

Development of a reactive burn model based on an explicit viscoplastic pore collapse model

Development of a reactive burn model based on an explicit viscoplastic pore collapse model

Mesoscale Simulation to Study Constitutive Properties of TATB/F2314 PBX

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

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