2D visualization and optimization of EMAT signal for small defect detection in thick plates

Abstract

The paper focus on a new combined experimental methodology and signal processing for an EMAT based on a Halbach magnet system in order to increase smaller defect detection in thick metallic plates. The visualization of the EMAT signal using a novel dynamic C-scan procedure is based on a continuous movement of the transducer above plate and an off-line signal processing that is enhanced and optimized for detection of small defects (5%) located on the opposite side of metallic plates (50 mm). The feasibility and performance of the acquisition signal method, and several signal processing algorithms are validated using experimental measurements. The results present an optimized two-dimensional visualization technique for EMAT signal, which can be used for continuous surface scans of plates for detection of smaller defects that self-calibrate as the scan is conducted.

Keywords

Nuclear reactor vessel austenitic stainless steel EMAT Halbach magnet array C-scan

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References

Urayama

Uchimoto

and Takagi

, Application of EMAT/EC dual probe to monitoring of wall thinning in high temperature environment, International Journal of Applied Electromagnetics and Mechanics33 (2010), 1317–1327.

Tagawa

Ueda

Characterization of SH wave electromagnetic acoustic transducer (EMAT) at elevated temperature, in: ASME/JSME Pressure Vessels and Piping Conference, Vol. PVP2004-2834, 2004, pp. 177–184.

Nakamoto

Kojima

Morikawa

Tabata

and Kosaka

, Pipe-wall thickness measurement at high temperature by electromagnetic acoustic transducer, Electromagnetic Nondestructive Evaluation (XVII)39 (2014), 256–262.

Hirao

and Ogi

, EMATs for Science and Industry: Non-contacting Ultrasonic Measurements, Kluwer Academic Publishers, Boston/Dordrecht/London, 2003.

Maxfield

B.W.

and Fortunko

C.M.

, The design use of electromagnetic acoustic wave transducers (EMATs), Materials Evaluation41 (1983), 1399–1408.

Urayama

Takagi

Uchimoto

and Kanemoto

, Online monitoring of pipe wall thinning by electromagnetic acoustic resonance method, E-Journal of Advanced Maintenance5 (2013), 155–164.

Sawaragi

Salzburger

H.I.

, Improvement of SH-wave EMAT phased array inspection by new eight segment probes, Nuclear Engineering and Design198 (2000), 153–163.

Kurozumi

Higashi

, Performance characteristics of electromagnetic generation and detection of shear horizontal waves by electromagnetic acoustic transducers, Materials Evaluation59-5 (2001), 638–644.

Yamaguchi

Mihalache

and Ueda

, Progress in developments of an EMAT based on a Halbach magnet system for FBR vessel, International Journal of Applied Electromagnetics and Mechanics59 (2019), 1469–1477.