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Proceedings Paper

Subnanosecond velocimetry with a new kind of VISAR
Author(s): Ken E. Froeschner; J. S. Froeschner; A. G. Youtsos; T. Timke; M. Kiriakopoulos
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Paper Abstract

A fresh approach to the principles of the delay leg interferometer which was ultimately developed by Barker, Hemsing and others as the `VISAR' (Velocity Interferometer System for Any Reflector) has resulted in an implementation which is simple, reliable, cost effective and capable of velocity measurements with sub-nanosecond time resolution. Results from laser induced shock exfoliation experiments which measure the adhesion strength of thin films on ceramic substrates are reported. These experiments require resolution of the shock structure produced by a 0.3 or 8 nanosecond Nd:YAG laser pulse interacting with a 0.5 to 1 micrometer thick energy absorbing layer deposited on the rear surface of the substrate/thin-film specimen, representative of an advanced turbine blade structure. Measurement of the velocity details of the film free surface during exfoliation, by Doppler shift of reflected laser light allows direct determination of the adhesion strength of the film/substrate interface at high strain rates and in ideal 1D plane strain conditions. The extremely small scale of the experiment requires very high time resolution. The Doppler Velocity Interferometer developed for these studies will be described in detail. Significant features include replacing the usual glass etalon with a zero-cost air delay leg, an extremely short optical path length, compact, rack- mounted configuration, all solid-state components including illumination by semiconductor diode laser and signal detection with sub-nanosecond PIN photodiodes.

Paper Details

Date Published: 28 May 1997
PDF: 7 pages
Proc. SPIE 2869, 22nd International Congress on High-Speed Photography and Photonics, (28 May 1997); doi: 10.1117/12.273411
Show Author Affiliations
Ken E. Froeschner, Martin, Froeschner & Associates (United States)
J. S. Froeschner, Martin, Froeschner & Associates (United States)
A. G. Youtsos, Commission of the European Communities Joint Research Ctr. (Netherlands)
T. Timke, Commission of the European Communities Joint Research Ctr. (Netherlands)
M. Kiriakopoulos, Commission of the European Communitites Joint Research Ctr. (Netherlands)

Published in SPIE Proceedings Vol. 2869:
22nd International Congress on High-Speed Photography and Photonics
Dennis L. Paisley; ALan M. Frank, Editor(s)

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