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EJAM2-1AA_SP1_"Quantitative Evaluation of Pipe Wall Thinning by Electromagnetic Acoustic Resonance"


Vol.1 No.4 GA 11 - 12 - AA SP1 (11 - 12 - 13 - 14) - NT 19 - 20 - 21 - 22 Vol.2 No.2
Academic Articles
Invited Paper	Vol.2 (2010) p.25 - p.33
Special Issue 1: "The Technology of Pipe-wall-thinning Management"

Quantitative Evaluation of Pipe Wall Thinning by Electromagnetic Acoustic Resonance

Ryoichi URAYAMA¹, Tetsuya UCHIMOTO¹, Toshiyuki TAKAGI¹, and Shigeru KANEMOTO²

¹Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ² School of Computer Science and Engineering, The University of Aizu, Japan

Abstract
Electromagnetic acoustic transducer (EMAT) provides non-contacting measurements and is often applied to monitoring in high temperature environment. One of drawbacks of EMAT is its low sensitivity and S/N ratio. One way to overcome the drawback is to introduce an Electromagnetic acoustic resonance method (EMAR); it has a high capability of evaluating thickness or ultrasonic velocity, and it is applied to the measurement of thickness, elastic constants, damping properties and so on. Since the principle of the method is based on the through-thickness resonances of bulk waves, that is, thickness oscillations, targets are usually limited to ones with simple geometry such as plates. In this study, pipe wall thinning, where the thickness changes on the curved surface, is evaluated by EMAR. For the purpose, several data processing methods are applied to extract thickness information from spectral responses. Measured spectra are obtained by an experiment using a carbon steel pipe with two-dimensional thinning machined by milling, and results of the data processing are compared in view of accuracy and stability. Finally, the data processing method is applied to the EMAR spectra of a pipe specimen cut from a mock-up test loop.

Keywords
EMAT, EMAR, Pipe wall thinning, Thickness measurement, Signal processing

Full Text: PDF

(Received: April 21st, 2010)


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