Steel is an important industrial material and is used in various structures. Nondestructive testing (NDT) is required to make sure that these structures meet the safety requirements and function as intended. Eddy current technique (ECT) is one of NDT techniques used for steel inspection. The use of ECT in steel inspection is generally, however, limited due to skin effect and magnetic property variations, particularly in sub-surface defect detection and quantification. This paper shows how DC magnetic saturation improves the sensitivity of pulsed eddy current (PEC) sensors in steel inspection and the theory behind it. Based on a modelling, a practical study has illustrated the advantages of the approach. A wavelet-based feature extraction developed from our previous work has been extended for defect classification of steel targets. Conclusions and further work are provided at the end of the paper.
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