Phase Contrast X‐Ray Imaging of the Collapse of an Engineered Void in Single‐Crystal HMX

Abstract

Imaging the collapse of a single void that creates a hot spot initiation site in an otherwise defect‐free explosive is challenging given the spatial and temporal scales involved in explosive systems. This work presents our attempt to examine a single hot spot mode (void collapse) in single‐crystal octahydro‐l,3,5,7‐tetranitro‐l,3,5,7‐tetrazocine (HMX) embedded in Sylgard. The hot spot heating mechanisms involved with pore collapse include adiabatic heating, jetting, and viscoplastic dissipation. Quantifying the dynamics of a pore collapse is a crucial step to understanding which mechanisms dominate during ignition events. Our experiments were conducted with a single‐stage, light‐gas gun at Argonne National Laboratory's Advanced Photon Source, applying the phase contrast imaging technique while collecting high‐speed video. The details of HMX single crystal production, defect (pore) engineering, and sample construction, along with experimental results are presented here. These results demonstrate that detailed collapse dynamics can be obtained from homogeneous, single‐crystal explosives with this approach. Qualitative comparisons are made with simulation data which show good agreement in the transition between a quasi‐symmetric pore collapse and an asymmetric collapse with jetting across the pore as measured with normalized pore area and pore circularity.

Sensitizing Explosives Through Molecular Doping

“…Additionally, this approach opens the door for “green” metal‐free primary energetics with reduced environmental and health concerns relative to toxic‐metal containing primary energetics, which are still widely used. Lastly, this approach provides a way to engineer a physical model for the hot spot mechanism of explosive ignition, an important field for understanding explosive performance that was established in the 1940s and that is still under active investigation today [42–44] …”

“…Lastly, this approach provides a way to engineer a physical model for the hot spot mechanism of explosive ignition, an important field for understanding explosive performance that was established in the 1940s and that is still under active investigation today. [42][43][44]…”

Effects of sub‐mm cylindrical voids on detonation performance in PBX 9501

“…Void location was varied for cut-back experiments, back surface streaks, and set to 3 mms for side streak imaging. The drilling operation followed the same procedure and used the same equipment that is presented in Blum-Sorensen et al [32].…”

“…The drilling operation followed the same procedure and used the same equipment that is presented in Blum‐Sorensen et al. [32].…”