In the inspection of the steel wall of the tank in the petrochemical plant etc., it is necessary to detect the opposite side defect from the surface of the steel wall. In this paper, the electromagnetic inspection method using alternating (ac) and static (dc) magnetic field is proposed. And, this method is investigated by verification experiment and 3-D nonlinear finite-element method (FEM) taking account of hysteresis(minor loop) and eddy current. It is shown that the detection of opposite side defect is possible by the differential permeability of minor loop of which the position on the hysteresis loop is affected by the existence of defect.
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2.
GotohY. and TakahashiN., Evaluation of Detecting Method with AC and DC Excitations of Opposite Side Defect in Steel using 3D Non-Linear FEM Taking Account of Minor Loop, IEEE Transactions on Magnetics44(6) (2008), 1622-1625.
3.
VertesyG., MeszarosI. and TomasI., Nondestructive indication of plastic deformation of cold-rolled stainless steel by magnetic minor hysteresis loops measurement, J. Magn. Magn. Mater.285(3) (2005), 335-342.
4.
MiyataK., OhashiK., MuraokaA. and TakahashiN., 3-D magnetic field analysis of permanent-magnet type MRI taking account of minor loop, IEEE Trans. Magn.42(4) (2006), 1452-1454.
