Non-uniform permeability distributions in steel materials reduce signal-to-noise (S/N) ratios in eddy current testing (ECT). Therefore, steel materials must be magnetised to reduce magnetic noise. In this study, microcrack detection in spring steel materials using ECT was considered. An ECT system that was able to detect 40-μm-deep crack with S/N ratio of 3 or more was developed. In addition, the depth profile of microcracks using the detection signal was accurately estimated.
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