All‐atom molecular dynamics (MD) and Eulerian continuum simulations, performed using the LAMMPS and SCIMITAR3D codes, respectively, were used to study thermo‐mechanical aspects of the shock‐induced collapse of an initially cylindrical 50 nm diameter pore in single crystals of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB). Three impact speeds, 0.5 km s−1, 1.0 km s−1and 2.0 km s−1, were used to generate the shocks. These impact conditions are expected to yield collapse mechanisms ranging from predominantly visco‐plastic to hydrodynamic. For the MD studies, three crystal orientations (relative to shock‐propagation direction) were examined that span the limiting cases with respect to the crystalline anisotropy in TATB. An isotropic constitutive model was used for the continuum simulations, thus crystal anisotropy is absent. The evolution of spatiotemporally resolved quantities during collapse is reported including local pressure, temperature, pore size and shape, and material flow. Multiple models for the melting curve and specific heat were studied. Within the isotropic elastic/perfectly plastic continuum framework and for the range of impact conditions studied, the specific heat and melting curve sub‐models are shown to have modest effects on the continuum hotspot predictions in the present inert calculation. Treating the MD predictions as ‘ground truth’, albeit with a classical rather than quantum‐like heat capacity, it is clear that – at a minimum – an extension of the constitutive model to account for crystal plasticity and anisotropic strength will be required for a high‐fidelity continuum description.
Initial hot spot temperatures and temperature evolutions for 4 polymer‐bound explosives under shock compression by laser‐driven flyer plates at speeds from 1.5–4.5 km s−1are presented. A new averaging routine allows for improved signal to noise in shock compressed impactor experiments and yields temperature dynamics which are more accurate than has been previously available. The PBX formulations studied here consist of either pentaerythritol tetranitrate (PETN), 1,3,5‐trinitro‐1,3,5‐triazinane (RDX), 2,4,6‐trinitrotoluene (TNT), or 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) in a 80/20 wt.% mixture with a silicone elastomer binder. The temperature dynamics demonstrate a unique shock strength dependence for each base explosive. The initial hot spot temperature and its evolution in time are shown to be indicative of chemistry occurring within the reaction zone of the four explosives. The number density of hot spots is qualitatively inferred from the spatially‐averaged emissivity and appears to increase exponentially with shock strength. An increased emissivity for formulations consisting of TNT and TATB is consistent with carbon‐rich explosives and in increased hot spot volume. Qualitative conclusions about sensitivity were drawn from the initial hot spot temperature and rate at which the number of hot spots appear to grow.
more » « less- NSF-PAR ID:
- 10137882
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Propellants, Explosives, Pyrotechnics
- Volume:
- 45
- Issue:
- 2
- ISSN:
- 0721-3115
- Page Range / eLocation ID:
- p. 338-346
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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