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Zhiwei Men1, Will P Bassett1, Kenneth S Suslick1

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Instrumented drop hammers reveal explosive initiation mechanisms. This study uses dual mid-wavelength infrared imagers to capture two-phase explosions in RDX and HMX, offering insights into impact sensitivity.

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Area of Science:

  • Materials Science
  • Chemical Engineering
  • Explosives Science and Technology

Background:

  • Drop hammer tests are standard for assessing explosive sensitivity.
  • Limitations exist in predicting explosive reactions to various stimuli based solely on low-velocity drop hammer impacts.
  • Understanding fundamental drop hammer initiation mechanisms is crucial for differentiating it from other initiation methods.

Purpose of the Study:

  • To develop an instrumented drop hammer for detailed analysis of explosive initiation.
  • To investigate the fundamental mechanisms of drop hammer initiation in polymer-bonded explosives.
  • To compare drop hammer initiation with other methods like ultrasonic hammering.

Main Methods:

  • Development of a novel drop hammer incorporating two mid-wavelength infrared (MWIR) imagers.
  • Simultaneous imaging with high temporal (1 μs) and spatial (15 μm) resolution to capture explosions and combustion.
  • Implementation of vibration isolation techniques to stabilize MWIR imaging during impact and quantification of noise floor for optical pyrometry.

Main Results:

  • Successfully captured impact-initiated explosions in RDX and HMX, revealing a two-phase reaction approximately 100 μs apart.
  • Demonstrated the capability of the instrumented drop hammer to detect both rapid explosion and slower combustion.
  • Quantified the vibration isolation effectiveness and noise floor for temperature measurements.

Conclusions:

  • The developed instrumented drop hammer provides unprecedented insight into the fundamental mechanisms of explosive initiation.
  • Drop hammer initiation involves a two-phase process, distinct from localized heating mechanisms seen in ultrasonic hammering.
  • The findings contribute to a better understanding of explosive behavior under impact, aiding in safety and performance evaluations.