EDDY CURRENT FLAW DETECTION METHOD AND DEVICE

PROBLEM TO BE SOLVED: To detect a signal due to foreign matter such as a surface flaw and a nonmetallic inclusion in the vicinity of a surface, out of an eddy current flaw detection signal of a specimen, without being affected by a false signal of an unevenness or the like, an electromagnetic noise...

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1. Verfasser: KODAMA TOSHIBUMI
Format: Patent
Sprache:eng
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Zusammenfassung:PROBLEM TO BE SOLVED: To detect a signal due to foreign matter such as a surface flaw and a nonmetallic inclusion in the vicinity of a surface, out of an eddy current flaw detection signal of a specimen, without being affected by a false signal of an unevenness or the like, an electromagnetic noise and the like, by a method dispensing with a significant additional facility. SOLUTION: In eddy current flaw detection impressing an alternating current as an excitation signal to an induction coil neighboring to the surface of the specimen to induce an eddy current in the vicinity of the specimen surface, and detecting a change of a magnetic field generated by a result of a change in the eddy current as a detection signal that is an electromotive force of a detection coil, a complex detection signal z(1) is formed using a signal component having a phase same to that of the excitation signal as a real number part x, a signal component having a phase difference of 90° with respect to that of the excitation signal as an imaginary number part y, and a relative distance l between the detection coil and the specimen as a parameter, out of the detection signal, and an abnormal part in the specimen is determined in the case where an output when a filter H(1) having an impulse response of a preset complex number acts on the detection signal exceeds a preset threshold value. COPYRIGHT: (C)2005,JPO&NCIPI