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Proceedings Paper

High resolution guided wave pipe inspection
Author(s): Alexander Velichko; Paul D. Wilcox
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Paper Abstract

Commercial guided wave inspection systems provide rapid screening of pipes, but limited sizing capability for small defects. However, accurate detection and sizing of small defects is essential for assessing the integrity of inaccessible pipe regions where guided waves provide the only possible inspection mechanism. In this paper an array-based approach is presented that allows guided waves to be focused on both transmission and reception to produce a high resolution image of a length of pipe. In the image, it is shown that a signal to coherent noise ratio of over 40 dB with respect to the reflected signal from a free end of pipe can be obtained, even taking into account typical levels of experimental uncertainty in terms of transducer positioning, wave velocity etc. The combination of an image with high resolution and a 40 dB dynamic range enables the detection of very small defects. It also allows the in-plane shape of defects over a certain size to be observed directly. Simulations are used to estimate the detection and sizing capability of the system for crack-like defects. Results are presented from a prototype system that uses EMATs to fully focus pipe guided wave modes on both transmission and reception in a 12 inch diameter stainless steel pipe. The 40 dB signal to coherent noise ratio is obtained experimentally and a 2 mm diameter (0.08 wavelengths) half-thickness hole is shown to be detectable.

Paper Details

Date Published: 8 April 2009
PDF: 10 pages
Proc. SPIE 7295, Health Monitoring of Structural and Biological Systems 2009, 72950W (8 April 2009); doi: 10.1117/12.815438
Show Author Affiliations
Alexander Velichko, Univ. of Bristol (United Kingdom)
Paul D. Wilcox, Univ. of Bristol (United Kingdom)

Published in SPIE Proceedings Vol. 7295:
Health Monitoring of Structural and Biological Systems 2009
Tribikram Kundu, Editor(s)

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