DC-Magnetization-Based Eddy Current Testing for Arbitrary Orientation Defects Detection in Ferromagnetic Steel

The dc-magnetization-based eddy current testing (ECT) has been developed, and probe signals according to defect orientations are investigated. A focusing field probe was highlighted to improve the sensitivity and compared with that of a circular pancake probe. The limit of the focusing field probe is a reduced sensitivity for parallel-oriented defects with lateral misalignment due to its narrow detection area, so this problem hinders the probe detecting arbitrary-oriented defects. Therefore, in this article, we have conducted simulation studies to investigate the effect of dc magnetization on signals of the probe with the different defect orientations. The results show that superimposing dc magnetization can widen the detection area of the probe on the application to ferromagnetic steel.