Comparison between temporal and spatial phase unwrapping for damage detection using shearography

A. V. Fantin; A. Dal Pont; D. P. Willemann; A. Albertazzi

doi:10.1117/12.693149

21 June 2006 Comparison between temporal and spatial phase unwrapping for damage detection using shearography

A. V. Fantin, A. Dal Pont, D. P. Willemann, A. Albertazzi

Proceedings Volume 6345, Seventh International Conference on Vibration Measurements by Laser Techniques: Advances and Applications; 634510 (2006) https://doi.org/10.1117/12.693149
Event: Seventh International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 2006, Ancona, Italy

Abstract

Shearography is an optical and nondestructive technique that has been largely used for damage detection in layered composite materials where delaminations and debondings are the most common flaws. In Shearography the sample under test is illuminated using a laser and imaged on a CCD camera. A special optical shearing element allows a coherent superposition of two laterally displaced images of the surface of the sample on the CCD plane. The images are recorded for different loading conditions of the sample. The loading should induce some deformation or alter the deformation state of the surface of the sample. In this work a thermal loading has been used. The absolute difference of two phase maps recorded at different loading situations of the sample results in an interference fringe pattern which is directly correlated to the difference in deformation state. The phase maps usually have strong noise and low contrast. For this reason, a further improvement in image quality should be obtained. Two methods, known as "difference of phases" and "phase of differences", are used with a spatial and temporal phase unwrapping algorithms, respectively, in an experiment using a steel pipe wrapped in a composite sleeve. A qualitative comparison of the methods is done and the results, advantages and difficulties are discussed.

Citation Download Citation

A. V. Fantin, A. Dal Pont, D. P. Willemann, and A. Albertazzi "Comparison between temporal and spatial phase unwrapping for damage detection using shearography", Proc. SPIE 6345, Seventh International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 634510 (21 June 2006); https://doi.org/10.1117/12.693149

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