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Proceedings Paper

Imaging of pipeline defects based on extraction of mode-converted guided waves
Author(s): Hyeonseok Lee; Hoon Sohn; Hyun Woo Park
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Paper Abstract

Guided waves are becoming popular for pipeline monitoring because of its sensitivity to small defects and long sensing range. Several research groups have explored ultrasonic imaging techniques for pipeline monitoring by fully utilizing the advantageous characteristics of guided waves. They have generated torsional mode and measured torsional reflections from pipe defects using expensive shear-mode piezoelectric transducers or electromagnetic acoustic transducers (EMAT), and then extracted crack-induced flexural modes as a post processing step. In this study, these existing techniques are further advanced to perform ultrasonic imaging by measuring the crack-induced flexural modes only, eliminating the necessity of the torsional mode information. This enables us to replace the expensive shear-mode transducers used to measure the torsional reflections with inexpensive compression-mode macro fiber composite (MFC) transducers. First, a magnetostrictive transducer attached at one end of the pipe is used for the excitation of a pure torsional mode in the pipe specimen. Then, the torsional mode propagates through the pipe, and the reflections are created by the interaction of the incident torsional mode with the crack. Due to the sensing characteristics of MFC transducers, only the crack-induced flexural modes can be measured by multiple MFC transducers placed along the circumference near the excitation magnetostrictive transducer. Using the normal mode expansion technique, each individual flexural mode among all reflected signals is extracted. By propagating this crack-induced flexural mode back in the space considering its dispersion characteristics, the location of the crack is visualized.

Paper Details

Date Published: 18 April 2012
PDF: 8 pages
Proc. SPIE 8348, Health Monitoring of Structural and Biological Systems 2012, 83480C (18 April 2012); doi: 10.1117/12.915508
Show Author Affiliations
Hyeonseok Lee, KAIST (Korea, Republic of)
Hoon Sohn, KAIST (Korea, Republic of)
Hyun Woo Park, Dong-A Univ. (Korea, Republic of)

Published in SPIE Proceedings Vol. 8348:
Health Monitoring of Structural and Biological Systems 2012
Tribikram Kundu, Editor(s)

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