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概要

Abstract Magnetic NDE of ferromagnetic steel using spectrum analysis of induced voltage at pick-up coil and magnetic induction has been studied. Magnetic yoke, having an excitation coil and a pick-up coil, was located on a specimen, and a sinusoidal current was applied to the excitation coil for magnetizing the specimen. A voltage induced at the pick-up coil was measured, and the corresponding magnetic in duction was calculated. Then, their frequency spectrums were obtained thorough Fourier analysis. For deformed specimen, higher harmonic components decrease as compared with undeformed specimen. Klirrfactors for the induced voltage and the magnetic induction were defined a nd evaluated. Those values decrease with increasing reduction ratio of the specimen; this means the waveforms of induced voltage and mag netic induction for a less deformed specimen has a large distortion in those waves. Those changes reflect nonlinearity of the magnetizat ion curve of specimen. The results in this study indicate a capability of Magnetic NDE using spectrum analysis of measurement wave forms.

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