MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Mechanics of Materials
Classification of Corrosion Flaws on Front and/or Back Surfaces of Non-Magnetic Metal Plates Using a Rectangular Wave Eddy Current Testing System
Teruyoshi Sasayama
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2023 Volume 64 Issue 1 Pages 220-226

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Abstract

If a rectangular wave excitation current is used for eddy current testing (ECT) instead of a sinusoidal wave, multifrequency testing can be performed directly because rectangular waves contain a fundamental wave as well as harmonic waves. Furthermore, considering the skin effect, it is possible to determine whether the specimen has a corrosion flaw on the front surface, back surface, or flaws on both surfaces. In this study, we first evaluate a method to classify these flaws on non-magnetic metal plates using rectangular wave ECT (RECT) systems with a linear amplifier. Here, we present an indicator in which each harmonic amplitude is divided by its fundamental amplitude. The results indicate that the amount of attenuation of the indicator in relation to the frequency depends on the type of flaw; therefore, we can classify the type of flaw using the indicator. Subsequently, we developed a RECT system with an inverter and conducted the same experiment. The results indicate that the tendency is the same as that when using the RECT system with a linear amplifier, which contributes to high efficiency, low cost, and weight reduction.

 

This Paper was Originally Published in Japanese in J. JSNDI 71 (2022) 215–221.

Fig. 9 RECT system with an inverter. Fullsize Image
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© 2022 The Japanese Society for Non-Destructive Inspection
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