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Proceedings Paper

Obtaining more information from time-of-flight-diffraction measurements
Author(s): Stuart B. Palmer; Steve Dixon; Phil A. Petcher
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Paper Abstract

Time of flight diffraction and imaging (TOFDI) is based on time of flight diffraction (TOFD); it adds cross-sectional imaging to examine the bulk of a sample. Multiple wave modes are generated by a pulsed laser beam, ablative source and are received by a sparse array of non-contact electromagnetic acoustic transducers (EMATs). A B-scan is formed from multiple data captures (A-scans), with time and scan axes, and colour representing amplitude. B-scans may contain horizontal lines from surface waves propagating directly from emitter to receiver, or via a back-wall reflection, and angled lines after reflection off a surface edge. A Hough transform (HT), modified to deal with the constraints of a Bscan, can remove such lines. A parabola matched filter has been developed to identify features in the B-scan caused by scattering from point-like features, reducing them to peaks. The processed B-scan is processed further to form a crosssectional image, enabling detection and positioning of multiple defects. Phase correlation of camera images is used to track the relative position between transducer and sample to sub-pixel precision.

Paper Details

Date Published: 4 April 2012
PDF: 12 pages
Proc. SPIE 8347, Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012, 83470Z (4 April 2012); doi: 10.1117/12.913605
Show Author Affiliations
Stuart B. Palmer, The Univ. of Warwick (United Kingdom)
Steve Dixon, The Univ. of Warwick (United Kingdom)
Phil A. Petcher, The Univ. of Warwick (United Kingdom)


Published in SPIE Proceedings Vol. 8347:
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2012
Andrew L. Gyekenyesi, Editor(s)

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