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Proceedings Paper

Speckle pattern correlation for local approach of damage evaluation
Author(s): Pierre R. Slangen; Patrick Ienny; Max Nemoz-Gaillard
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Paper Abstract

Optical techniques because there are no-contact and non intrusive methods are well suited for non destructive testing and for damage evaluation. Image correlation is well suited in mesoscopic approach between successive steps of deformation and can be achieved if the object under study is carrying a characteristic pattern. As a characteristic pattern the white light image of the object surface or the subjective speckle generated by coherent illumination of an optically rough object can be used. The image is then grabbed by a high resolution CCD camera. Instead of using a defined mesh on the object, image correlation allows dynamic link of a point to a pixels pattern called the correlation window. While applying stress or strain, points of the object surface are moving. Between each step of deformation the correlation window and the mesh are then updated. While using a tensile test apparatus the rigid body motion is compensated by moving the CCD camera on a parallel axis to keep the region of interest into the field of view. All the operations are computer-controlled under data acquisition and processing software. The results are presented as in- plane displacement vectors and allow the determination of some mechanical values by external computing. The method is applied to damage analysis from in-situ measurements in concrete manufacture.

Paper Details

Date Published: 18 September 1996
PDF: 12 pages
Proc. SPIE 2782, Optical Inspection and Micromeasurements, (18 September 1996); doi: 10.1117/12.250771
Show Author Affiliations
Pierre R. Slangen, Ecole des Mines d'Ales (France)
Patrick Ienny, Ecole des Mines d'Ales (France)
Max Nemoz-Gaillard, Ecole des Mines d'Ales (France)

Published in SPIE Proceedings Vol. 2782:
Optical Inspection and Micromeasurements
Christophe Gorecki, Editor(s)

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