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Title: Non-contacting transfer of elastic energy into explosive simulants for dynamic property estimation

Non-contacting acoustical methods can be used to extract various material properties of liquid or solid samples without disturbing the sample. These methods are useful even in the lab since they do not involve coupling anything to the sample, which might change its properties. A forteriori, when dealing with potentially dangerous materials, non-contacting methods may be the only safe solutions to mechanical characterization. Here, we show examples of using laser ultrasound to remotely insonify and monitor the elastic properties of several granular explosive simulants. The relatively short near-infrared laser pulse length (a few hundred nanoseconds) provides a broad-band thermoelastic source of ultrasound; we intentionally stay in the thermoelastic regime to avoid damaging the material. Then, we use a scanning laser Doppler vibrometer to measure the ultrasonic response of the sample. LDV technology is well established and very sensitive at ultrasonic frequencies; atomic level motions can be measured with modest averaging. The resulting impulse response of the explosive simulant can be analyzed to determine decay rates and wave speeds, with stiffer samples showing faster wave speeds and lower decay rates. On the other hand, at the low-frequency end of the acoustic spectrum, we use an electronically phased array to couple into amore » freely suspended sample's normal modes. This allows us to gently heat up the sample (3 °C in just under 5 min, as shown with a thermal IR camera). In addition to the practical interest in making the sample more chemically visible through heat, these two measurements (low-frequency resonant excitation vs high-frequency wave propagation) bracket the frequency range of acoustic non-destructive evaluation methods available.« less
Authors:
; ;  [1] ; ;  [2] ; ;  [3]
  1. Physics Department, Colorado School of Mines, Golden, Colorado 80401 (United States)
  2. Ray W. Herrick Laboratories, Purdue University, West Lafayette, Indiana 47907-2099 (United States)
  3. Purdue Center for Systems Integrity, Purdue University, Lafayette, Indiana 47905 (United States)
Publication Date:
OSTI Identifier:
22304410
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 19; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COUPLING; DOPPLER EFFECT; ELASTICITY; EVALUATION; EXCITATION; EXPLOSIVES; GRANULAR MATERIALS; LASER RADIATION; LASER-RADIATION HEATING; LIQUIDS; SOLIDS; SPECTRA; WAVE PROPAGATION