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Proceedings Paper

High-resolution dynamic photoelastic study of laser-generated sound in polymer
Author(s): David C. Emmony; M. K.B. Suaidi; Y. H. Jin; Barry Ward
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Paper Abstract

The interaction of laser radiation with materials can lead to the generation of thermal and acoustic transients. If the laser pulse is of short duration and high power as in the case of a Q switched Nd YAG laser, then shock waves may be formed with fast rising pressure fronts. The optical diagnostics of laser generated sound waves therefore requires high spatial, approximately 10 micrometers , and high temporal, approximately 10 ns, resolution, in order to make quantitative measurements. A nitrogen laser pumped dye laser with a pulse length of 0.4 ns has been used as the light source for a Mach-Zehnder interferometer. The interferometer was modified to enable dynamic photoelastic interferograms to be taken. Recording was by means of a CCD video camera and computer controlled digitizing frame grabber. This system has been employed to study laser generated waves at water-polymer boundaries and the diffraction of ultrasound by defects in the solid material. The isochromatic fringe patterns, together with an approximate Abel inversion procedure, allow the radial pressure distribution in the polycarbonate test samples to be calculated. The ultimate aim is to obtain the near field diffraction coefficients for use in NDT modeling.

Paper Details

Date Published: 1 January 1993
PDF: 12 pages
Proc. SPIE 1801, 20th International Congress on High Speed Photography and Photonics, (1 January 1993); doi: 10.1117/12.145789
Show Author Affiliations
David C. Emmony, Loughborough Univ. of Technology (United Kingdom)
M. K.B. Suaidi, Loughborough Univ. of Technology (United Kingdom)
Y. H. Jin, Loughborough Univ. of Technology (United Kingdom)
Barry Ward, Loughborough Univ. of Technology (United Kingdom)

Published in SPIE Proceedings Vol. 1801:
20th International Congress on High Speed Photography and Photonics
John Marks Dewey; Roberto G. Racca, Editor(s)

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