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Book: Studies in Applied Electromagnetics and Mechanics 10, Nonlinear Electromagnetic Systems, Editors: A.J. Moses and A. Basak, IOS Press, Amsterdam (1996), ISBN: 90-5199-251-3, pp.748-751

New Electromagnetic NDT Technique for the Detection of Discontinuities in Metallic Plates

Csaba Sándor DARÓCZI(a), János SZÖLLŐSY(a), Gábor VÉRTESY(a), József PÁVÓ(b) and Kenzo MIYA(c)

(a) Hung. Acad. Sci., Research Institute for Materials Science ATKI, H-1525 Budapest, P.O. Box 49, Hungary
(b) Technical University of Budapest, Dept. Electromagnetic Theory, H-1521 Budapest, Hungary
(c) Nuclear Engineering Research Laboratory, The University of Tokyo, Tokai, Ibaraki, 319-11, Japan

A new high-sensitive ECT measuring technique is presented which has been developed recently to discover internal discontinuities in metallic specimens. The technique is based on the combination of the detection of the magnetic flux density (B) changes due to the eddy currents and the variation of the magnetic polarization (P) of the sample. The eddy current field is generated by an exciting coil located on one side of the specimen. Separate detector coils are used to measure the changes of the magnetic field in the case of an inhomogeneous sample which are sensitive in X and in Y directions parallel with the sample surface, respectively. The exciting frequency is in the kHz range depending on the thickness, the electrical conductivity and the relative permeability of the sample. Compared to the conventional ECT methods our technique can give improved sensitivity and lateral resolution, simultaneously in X and in Y directions. Scanning the probe over the sample surface and utilizing computer (PC) controlled data acquisition/evaluation systems the magnetic image of the sample can also be obtained.

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