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Proceedings Paper

Conical Convergent Shock Fronts In Pmma Measured By Optical Streak Photography, X-Ray Flash, And .Piezoresistive Pressure Sensors
Author(s): Bao-Ping Zhang; K. Hollenberg; H.R. KleinhanB
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Paper Abstract

The conical convergent shock wave in a cylindrical specimen can bring forth Mach reflection, e.g. the shock wave overcomes the singularity on the axis by performing a triple point between the incoming front, the head wave and the reflected shock wave. The conical convergent shock wave is produced by the explosion of a high explosive which forms the outer coating of the probe. If the detonation is made running parallel to the axis of the probe the head wave - Mach disk -runs in the same direction with the detonation velocity of the outer explosive. In water all the three types of shock waves were detected as well from X-ray flash photographs as by measuring the electrical conductivity of the water under shock load. X-ray flash photographs of PMMA (Polymethylmetacrylat) specimens in contrast to the experiments with water show no triple point configuration. On top of the incoming shock wave cone a shock wave with steady curvature is observed. The centre part of this shock wave is nearly plane and stands perpendicular to the axis of the probe. There is no evidence for a reflected shock front. Optical streak photographs of the PMMA probes were made using several collapsing argon gaps. The results obtained by this method are very similar to those known from literature. A distance of about three times the probe diameter is necessary to get a stable shock configuration. The interpretation of the streak records is made difficult by the great range of intensity within one streak curve. The centre zone shows very little light due to the rapid closure of the gap due to the nearly parallel striking of the shock wave. The results were confirmed by time resolved pressure measurements with composite carbon resistors which have a great piezoresistive coefficient. From these experiments the shock contours were reconstructed with 10 ns time resolution in accordance with the optical and X-ray measurements. The pressure records too show no second pressure jump of a reflected shock front in PMMA.

Paper Details

Date Published: 1 February 1985
PDF: 7 pages
Proc. SPIE 0491, 16th Intl Congress on High Speed Photography and Photonics, (1 February 1985); doi: 10.1117/12.967983
Show Author Affiliations
Bao-Ping Zhang, Peking Institute of Technology (China)
K. Hollenberg, Universitat Dusseldorf (Germany)
H.R. KleinhanB, Universitat Dusseldorf (Germany)

Published in SPIE Proceedings Vol. 0491:
16th Intl Congress on High Speed Photography and Photonics
Michel L. Andre; Manfred Hugenschmidt, Editor(s)

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