Study on Induced Current Focusing Potential Drop (ICFPD) Technique: —Improvement of Probe and Application for the Estimation of 2-Dimensional Surface Defect —

ICFPD technique has been developed to detect nondestructively the defects and to estimate their sizes in components with not only simple shape such as plain surface but also more complex shape and geometry such as curved surface and dissimilar joint. In this technique a constant alternating current is induced in an exploratory region by a straight induction wire and potential drops are measured by the potential pick-up pins of which spacing is constant. In this study, new improvements have been made on the probe material and induction wire in order to solve the problems encountered in aluminum probe (Al. probe) used in the 1st report. The new probe (Ac. probe) is made of non-conductive acrylic resin. The specimens with 2-dimensional surface defects were evaluated by this probe. It was shown that the surface defects could be detected by the difference of potential drop, and the shape of potential drop distribution was similar for each specimen irrespective of defect depth and measuring frequency. It was also found that, for the depth less than 5 mm. the ICFPD technique had higher sensitivity than the conventional ACPD.