The rotating field eddy current probe was successfully scaled down for use in detecting OD initiated flaws in 0.5 in. diameter, non-magnetic tubing. The probe produces a bipolar response on circumferential EDM notches. The phase angle of this response is easily identified and measured. The phase of the response changes with flaw depth and also exhibits the expected response to changes in frequency. The data presented here indicate that the rotating field probe can be used to estimate the depth of circumferential crack-like flaws. Notches with depths as shallow as 40% of the wall thickness were clearly measured. The 20% notch, which is easily detected with the conventional plus point probe, was not clearly discernible with this probe. However, these measurements were made with a proof-of-principle probe made from materials on hand, and was not optimized.
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