Fundamental study on smart eddy current testing for identification of crack orientation by controlling electromagnetic field using electrically anisotropic plate

This work proposes a smart eddy current testing (ET) method for identifying crack orientation by introducing an additional electrically anisotropic plate. The key idea of the proposed approach is to insert the anisotropic plate between an eddy current (EC) probe and a test piece for controlling the electromagnetic field. Distribution of the space magnetic field and induced current density was numerically investigated. The simulation results showed that deformation of the magnetic field distribution occurs in the case of inserting an anisotropic plate. Meanwhile, it makes the magnetic field distribution directional and its direction will be changeable and controllable by rotating angle θ of the anisotropic plate. Furthermore, redistribution of the induced current density can be observed in the test piece, which results in two identical peak areas, and they are symmetric with respect to an axis perpendicular to the rotation angle. Subsequently, output voltage of the EC probe was calculated to quantitatively analyze the sensitivity for identifying crack orientation. Findings show that the output voltage from the probe was affected by the angle between the conductivity angle θ of the anisotropic plate and the crack orientation.