Measurement and Evaluation of Pipe Wall Thinning by Electromagnetic Acoustic Resonance
兼本 茂 Shigeru KANEMOTO 浦山 良一 Ryo-ichi URAYAMA 内一 哲哉 Tetsuya UCHIMOTO 高木 敏行 Toshiyuki TAKAGI
EMAREMATPipe Wall ThinningSignal ProcessingThickness Measurement
Electromagnetic acoustic transducer (EMAT) provides non-contacting measurements and is often applied to monitoring in gh temperature environment. One of drawbacks of EMAT is its low sensitivity and S/N ratio. One way to overcome the uwback is to introduce an Electromagnetic acoustic resonance meth od (EMAR); it has a high capability of evaluating ckness or ultrasonic velocity, and it is applied to the measurement of thickness, elastic constants, damping propertiesso on. Since the principle of the method is based on the resonances of bulk waves in plates, that is, thickness cillations, targ ets are usually limited to ones with simple geometry. In this study, pipe wall thinning, where the thickness anges on the curved surface, is evaluated by EMAR. For the purpose, several data processing methods are applied to Cract thickness information from EMAR spectral responses. Measured spectra are obtained by an experiment using a bon steel pipe with two-dimensional thinning machined by milling, and results of the data processing are compared in w of accuracy and stability. Finally, the data processing method is applied to the EMAR spectra of a pipe specimen cut m a mock-up test loop.