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Proceedings Paper

Application_Of_Holographic_Interferometry To Problems In Geophysics And Detonics
Author(s): D. C. Holloway; W. H. Wilson
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Paper Abstract

Holographic interferometry, with a Q-switched Ruby laser, has been used for laboratory study of dynamic problems in geophysics and detonics. The holograms provided not only the images of transient phenomena not visible in ordinary high speed photography, but also the data needed to analyze wave speeds and particle motions in solids, or density and pressure in gasses. Explosively driven cracks in rock plates have been studied dynamically by a modification to the usual timing sequence, in which both laser pulses occur after the explosive loading, and within less than a microsecond of each other. Changes in surface displacements, due to the stress wave motion in the model between exposures, cause interferometric fringes which are discontinuous along crack boundaries in the material. This method has successfully located cracks which would not be visible by normal optical methods. Surface and near-surface disturbances propagating in the earth from blasting sites were studied. Three-dimensional models were explosively loaded at points on the model surfaces. Holograms made at various delay times after loading showed the model's surface motions due to waves propagating from the source. Interactions of waves from two neighboring sources and wave interactions with steps and trenches in the model surface have been analyzed. Rayleigh waves crossing trenches were shown to undergo significant reductions in total particle displacement, particle velocity, and frequency content. It was also shown that as the diltational wave crosses steps or trenches, a substantial new Rayleigh wave is generated and propagates ahead of the source Rayleigh wave. Air shock due to explosive detonations has also been studied. Transmission holograms were made of the shock wave at the open end of a fine tube internally lined with an explosive coating.

Paper Details

Date Published: 1 February 1985
PDF: 30 pages
Proc. SPIE 0491, 16th Intl Congress on High Speed Photography and Photonics, (1 February 1985); doi: 10.1117/12.968047
Show Author Affiliations
D. C. Holloway, University of Maryland (United States)
W. H. Wilson, University of Maryland (United States)

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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