Thermal and Mechanical Response of PBX 9501 and Simulants Under High Frequency Contact Excitation

Jesus Ortega Mares, Purdue University

Abstract

Stand-off detection of explosives through trace vapor detection remains a distinct challenge due to the low vapor pressures of these materials. However, it is known that the vapor concentration of these explosives may be significantly increased by elevating the temperature of the material. It is plausible that improvements in the detection of explosives might be realized through the use of mechanical excitation. In this work PBX 9501 (an HMX-based explosive), two mechanical mock materials 900-21, and PBS 9501 were insulted with contact mechanical excitation in the frequency range of 50 kHz to 40 MHz. The mechanical response of each sample was measured via ultrasound transducers and was confirmed via laser Doppler vibrometry up to a frequency of 1 MHz. Steady-state thermal responses were observed via infrared thermography at discrete frequencies spanning the full frequency range of interest. Temperature excursions of approximately 15 K were observed in PBX 9501 and similar results were observed from the mock materials. The mechanisms for heat generation within these materials were found to be highly dependent on the frequency range of excitation. Heat generation at lower frequencies corresponding to structural resonances is likely driven by bulk motion of the sample. Above these frequencies, wavelength-scale interactions of the particles and binder are proposed to be the main contributor to heating. The observed phenomenon may prove useful in the aid of current trace vapor detection methods for explosives.

Degree

M.S.E.

Advisors

Son, Purdue University.

Subject Area

Mechanical engineering|Materials science|Acoustics

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