Initiation of granular explosives by ramp waves
Conference
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OSTI ID:5710014
Initiation processes in granular explosives experiencing finite-risetime loading, in contrast to shock loading, have been investigated experimentally. Ramp waves having a risetime of either 0.3 ..mu..s or 0.8 ..mu..s were transmitted into the explosive PBX-9404, resulting in initial waves having a peak axial stress of 5.1 GPa. The incident waves were generated in discs of a glass-ceramic, pyroceram, by planar impact of copper-faced projectiles using a gas-fired gun facility. Velocity interferometry (VISAR) was used to measure particle velocity histories after the initial wave had propagated through explosive samples having different thicknesses. For comparison, similar measurements were made for the case of shock loading to the same initial peak stress. The slower-rising ramp wave initially loads the explosive at an average rate of 7 GPa/..mu..s. The VISAR measurements show that initiation processes leading to detonation are strongly inhibited at such a rate of compression. After a propagation distance of 4.0 mm this ramp wave has steepened into a shock, but a relatively small rise in particle velocity following the shock suggests that little chemical energy has been released. Thus, velocity profiles measured up to this position provide detailed information on the mechanical characteristics of the unreacted explosive. After propagating 5.0 mm this wave has evolved into a stronger shock, with clear evidence of compressive disturbances being generated behind this wave. Comparisons between this profile and the shock-initiation profiles, however, show that shock loading results in much more rapid growth towards detonation. After propagating 3.0 mm the shock-input measurements show far more evidence of chemical energy release, with full detonation predicted for this case by 5.0 mm.
- Research Organization:
- Sandia Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 5710014
- Report Number(s):
- SAND-79-1169C; CONF-790975-5
- Country of Publication:
- United States
- Language:
- English
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