Ignition criterion for heterogeneous energetic materials based on hotspot size-temperature threshold

A. Barua, S. Kim, Y. Horie, M. Zhou

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92 Scopus citations

Abstract

A criterion for the ignition of granular explosives (GXs) and polymer-bonded explosives (PBXs) under shock and non-shock loading is developed. The formulation is based on integration of a quantification of the distributions of the sizes and locations of hotspots in loading events using a cohesive finite element method (CFEM) developed recently and the characterization by Tarver [C. M. Tarver, Critical conditions for impact- and shock-induced hot spots in solid explosives, J. Phys. Chem. 100, 5794-5799 (1996)] of the critical size-temperature threshold of hotspots required for chemical ignition of solid explosives. The criterion, along with the CFEM capability to quantify the thermal-mechanical behavior of GXs and PBXs, allows the critical impact velocity for ignition, time to ignition, and critical input energy at ignition to be determined as functions of material composition, microstructure, and loading conditions. The applicability of the relation between the critical input energy (E) and impact velocity of James [H. R. James, An extension to the critical energy criterion used to predict shock initiation thresholds, Propellants, Explos., Pyrotech. 21, 8-13 (1996)] for shock loading is examined, leading to a modified interpretation, which is sensitive to microstructure and loading condition. As an application, numerical studies are undertaken to evaluate the ignition threshold of granular high melting point eXplosive, octahydro-1,3,5,7-tetranitro-1,2,3,5-tetrazocine (HMX) and HMX/Estane PBX under loading with impact velocities up to 350 ms-1 and strain rates up to 105 s-1. Results show that, for the GX, the time to criticality (tc) is strongly influenced by initial porosity, but is insensitive to grain size. Analyses also lead to a quantification of the differences between the responses of the GXs and PBXs in terms of critical impact velocity for ignition, time to ignition, and critical input energy at ignition. Since the framework permits explicit tracking of the influences of microstructure, loading, and mechanical constraints, the calculations also show the effects of stress wave reflection and confinement condition on the ignition behaviors of GXs and PBXs.

Original languageEnglish
Article number064906
JournalJournal of Applied Physics
Volume113
Issue number6
DOIs
StatePublished - Feb 14 2013
Externally publishedYes

Funding

The authors gratefully acknowledge support from the Air Force Research Laboratory (AFRL) at the Eglin AFB in Florida and the Defense Threat Reduction Agency (DTRA) (scientific officer: Dr. Suhithi Peiris). Calculations are carried out on parallel computers at NAVO and the DPRL at Georgia Tech.

FundersFunder number
Defense Threat Reduction Agency
Air Force Research Laboratory

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