Measurement of Shock Wave and Particle Velocities in Shocked Dielectric Material from Millimeter-Wave Remote Sensing

Abstract

A millimeter-wave remote sensing technique is used here as a noninvasive and continuous approach for the real-time measurement of shock wave velocity as well as the velocity of the shocked dielectric material during an impact. Experimental results obtained from planar symmetric impacts on PolyMethyl MethAcrylate (PMMA) cylinders are discussed and demonstrate that the proposed millimeter-wave remote sensing technique is highly convenient for deriving both the velocity of the shock wave and velocity of the shocked PMMA material. The proposed approach is applicable to any dielectric material subject to an impact and is an excellent candidate for deriving the equation of state of shocked materials.

Shock Properties Characterization of Dielectric Materials Using Millimeter-Wave Interferometry and Convolutional Neural Networks

“…However, we continue to observe large deviations for the DFA method. As typical experimental values for the correlation coefficient are between 0.9 and 0.99 [10], the NNA should then be preferred when processing short-duration waveforms, especially for estimating the particle velocity V2 and refractive index N2 of the shocked medium. Table 4.…”

“…The determination of C 0 and s has been the subject of many studies (see, e.g., [2]) and is usually performed from the measurement of V 1 and V 2 [3,4] by using research guns with light gas or powder [5], laser shock [6] or explosives set-ups [7]. Non-invasive techniques were reported to remotely and simultaneously derive the shock wave velocity V 1 , the particle velocity V 2 and possibly the refractive index N 2 of the shocked medium from the measurement of two Doppler frequencies in the waveform delivered by a radiofrequency interferometer [8][9][10][11][12][13]. The Doppler effect is a phenomenon where the perceived frequency of sound, light waves or electromagnetic waves changes depending on the relative motion of the source and observer.…”

“…The noise could be reduced by choosing the lowest oscilloscope caliber in order to avoid signal saturation. We have observed that, for waveforms of sufficiently long duration (>5 µs), the detection and accurate estimation of two Doppler frequencies from the two sinus functions' fitting technique are possible (see, e.g., [9,10] for the investigation of shocked PolyMethylMetAcrylate dielectrics and TriAminoTrinitroBenzene solids, respectively). However, as the waveform duration decreases and is only of a few microseconds, even less than the pulsation period, lower Doppler frequencies may not be accurately estimated, and consequently, the wavefront and particle velocities V 1 and V 2 cannot be derived from the fitting technique reported in [8].…”

Polymer chirped fiber Bragg grating for more sensitive shock velocity measurements

“…A pillar was 3D-printed (in white) and glued to the yellow electrical pins holder. A microwave interferometer (RIF for radio interferometer) [18] with a 94-GHz frequency was also used. A RIF allows measuring the displacement of the shock/detonation wave through the HE material knowing its microwave refractive index.…”