Pre-ignition confinement and deflagration violence in LX-10 and PBX 9501
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
In thermal explosions of the nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based explosives LX-10 and PBX-9501, the pre-ignition spatial and temporal heating profile defines the ignition location. The ignition location then determines the extent of inertial confinement and the violence of the resulting deflagration. In this work, we present results of experiments in which ∼23 g cylinders of LX-10 and PBX 9501 in thin-walled aluminum confinement vessels were subjected to identical heating profiles but which presented starkly different energy release signatures. Post-explosion LX-10 containment vessels were completely fragmented, while the PBX 9501 vessels were merely ruptured. Flash x-ray radiography images show that the initiation location for the LX-10 is a few mm farther from the end caps of the vessel relative to the initiation location of PBX 9501. This difference increases deflagration confinement for LX-10 at the time of ignition and extends the pressurization time during which the deflagration front propagates in the explosive. The variation in the initiation location, in turn, is determined by the thermal boundary conditions, which differ for these two explosives because of the larger coefficient of thermal expansion and greater thermal stability of the Viton binder in LX-10 relative to the estane and bis(2,2-dinitropropyl) acetal/formal binder of the PBX 9501. The thermal profile and initiation location were modeled for LX-10 using the hydrodynamics and structures code ALE3D; results indicate temperatures in the vicinity of the ignition location in excess of 274 °C near the time of ignition. The conductive burn rates for these two explosives, as determined by flash x-ray radiography, are comparable in the range 0.1–0.2 mm/μs, somewhat faster than rates observed by strand burner experiments for explosives in the temperature range 150–180 °C and pressures up to 100 MPa. The thinnest-wall aluminum containment vessels presented here rupture at lower pressures, in the range 10 MPa, suggesting that moderately higher temperatures and pressures are present near the deflagration front. For these explosives, however the most important property for determining deflagration violence is the degree of inertial confinement.
- OSTI ID:
- 22314574
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 5 Vol. 116; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACETAL
ALUMINIUM
BINDERS
BOUNDARY CONDITIONS
BURNERS
COMPARATIVE EVALUATIONS
CONTAINMENT
CYLINDERS
EXPLOSIONS
EXPLOSIVES
HEATING
HYDRODYNAMICS
INERTIAL CONFINEMENT
PRESSURE RANGE MEGA PA 100-1000
PRESSURIZATION
RUPTURES
TEMPERATURE RANGE 0400-1000 K
THERMAL EXPANSION
WALLS
X-RAY RADIOGRAPHY