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Proceedings Paper

Characterization of defects in plates by two-dimensional ultrasonic displacement maps: comparison between pulsed TV-holography measurements and finite element method predictions
Author(s): P. Rodríguez-Gómez; J. Carlos López-Vázquez; Cristina Trillo; Ángel F Doval; José L. Fernández
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Paper Abstract

Pulsed TV-holography (PTVH) can be used for obtaining two-dimensional maps of instantaneous out-of-plane displacements in plates. In particular, scattering patterns generated by the interaction of elastic waves with defects can be measured with PTVH and employed for non-destructive inspection and damage detection in plate structures. For quantitative characterization of damage (position, dimensions, orientation, etc.) on this basis, modeling of elastic wave scattering is usually performed in terms of full-vector three-dimensional formulations based on elasticity theory. In this work, a finite element method (FEM) applied to a two-dimensional scalar model based on Helmholtz equation is employed for obtaining a quantitative description of the scattering patterns, avoiding the aforementioned more complex and rigorous standard approach. Simulated scattering patterns are obtained with the scalar FEM assuming harmonic regime and free-stress boundary conditions. The corresponding experimental interaction of narrowband Rayleigh-Lamb waves with artificial defects in plates are measured using our specifically developed PTVH system. In our case, the raw optical phase-difference values are processed by employing a specially developed procedure, based on a two step spatial Fourier transform method, to derive a high quality two-dimensional acoustic field map from which an important part of the noise component has been filtered out. A comparison between filtered experimental maps and FEM simulated maps is developed, considering defects with different sizes in relation to the acoustic wavelength.

Paper Details

Date Published: 13 September 2010
PDF: 10 pages
Proc. SPIE 7387, Speckle 2010: Optical Metrology, 73871I (13 September 2010); doi: 10.1117/12.870769
Show Author Affiliations
P. Rodríguez-Gómez, Univ. de Vigo (Spain)
J. Carlos López-Vázquez, Univ. de Vigo (Spain)
Cristina Trillo, Univ. de Vigo (Spain)
Ángel F Doval, Univ. de Vigo (Spain)
José L. Fernández, Univ. de Vigo (Spain)

Published in SPIE Proceedings Vol. 7387:
Speckle 2010: Optical Metrology
Armando Albertazzi Goncalves Jr.; Guillermo H. Kaufmann, Editor(s)

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