| Title | Simulations Explain Detonation Properties in TATB | |
| Date | Thursday May 28 2020, @10:06AM | |
| Author | martyb | |
| Topic | ||
| from the things-that-make-you-go-hmmmn?-BOOM! dept. | ||
Arthur T Knackerbracket has found the following story:
Two Lawrence Livermore National Laboratory (LLNL) scientists have discovered a new mechanism for ignition of high explosives that explains the unusual detonation properties of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).
[...] Highly insensitive explosives offer greatly enhanced safety properties over more conventional explosives, but the physical properties responsible for the safety characteristics are not clear. Among explosives, TATB is nearly unique in its safety-energy trade-offs.
Engineering models for shock initiation safety and detonation performance of explosives rely on physics models that center on the formation and growth of hot spots (local regions of elevated temperature that accelerate chemical reactions) thought to govern these responses. However, models for TATB based on the hot spot concept have so far been unable to simultaneously describe both initiation and detonation regimes. This indicates missing physics in the fundamental understanding of what processes drive insensitive high explosives to detonate.
[...] Answering questions regarding the chemical reactivity of shear bands required turning to quantum-based molecular dynamics (QMD) simulation approaches and high performance computing. "The main challenge with QMD is that it can only be applied to small systems, so we developed a multiscale modeling technique to look at the chemistry of shear band and crystal regions in representative volume elements," explained Matt Kroonblawd, lead author on the study.
Through scale bridging with QMD, the team found that disordered material in shear bands becomes chemically activated. The bands are formed in strongly shocked TATB and react 200 times faster than the crystal, which gives a physical explanation for why engineering models required empirical "switching functions" to go between shock initiation and detonation situations.
Journal Reference:
Matthew P. Kroonblawd, et al. "High Explosive Ignition through Chemically Activated Nanoscale Shear Bands", Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.124.206002
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