Double-exposure holography and shearography are two laser-based techniques which have been used recently for detecting and assessing debonds in laminated plates. When a plate is tested with am incremental partial vacuum pressure between the two exposures, the boundary of the amomalous fringes reveals the shape and size of a debond; the number of these fringes enables estimation of the depth of the debond. Various difficulties are encountered in interpreting these fringes, for example, accurate determination of the number of anomalous fringes which are generally few, and the identification and assessment of overlapping debonds. This paper addresses some of these difficulties and presents methods of overcoming or alleviating them so that the potential of holography and shearography in NDT may be further enhanced.

Date Published: 1 December 1991
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Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991); doi: 10.1117/12.57458

Published in SPIE Proceedings Vol. 1554:
Second International Conference on Photomechanics and Speckle Metrology
Fu-Pen Chiang; Fu-Pen Chiang, Editor(s)