Numerical Modeling of Projectile Impact Shock Initiation of Bare and Covered Composition-B
Final technical rept.
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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This report concerns our numerical modeling of the projectile impact shock initiation of composition-B comp-B. We have considered both bare and covered charges impacted by cylindrical steel projectiles using the Los Alamos 2DE code. We have examined the flow fields in some detail and compared predicted critical velocities with published experimental values. For bare charges, we observed two different mechanisms by which the critical velocity is determined. For impacts by projectiles of sufficiently large diameter initiation occurs as the impact induced shock wave builds to detonation by reinforcement due to burning behind the shock. For smaller diameter, high velocity projectiles, we saw that detonation or near detonation breaks out immediately on impact, but may be quenched by the ensuing rarefactions. We found that 2DE predicted the critical velocity accurately. We compared the shock to detonation transition paths to the Pop-plot for comp-B and found them to agree in the case of a planar shock buildup but not in the case of projectile impact, for which multiple paths to detonation were observed. We also simulated the special projectile geometries considered by Moulard and found that 2DE provided a qualitative explanation of his observations. In the case of covered projectiles we found flow fields similar to the bare charge case. The thickest cover plates allowed the rarefaction to overtake the shock before they entered the explosive and significantly raised the critical velocity. The predicted initiation thresholds agree with Howes results but not with Slade and Deweys.
- Numerical Mathematics
- Ammunition and Explosives