Nondestructive evaluation of hardness using AC permeability and impedance analysis

The equivalent circuit for the relation between the impedance of the coil wound around the magnetic yoke and the permeability of the material was analyzed for a quantitative estimation of an initial permeability of materials from the impedance measurement of the magnetic yoke. The optimum design of the magnetic yoke for an impedance measurement is also considered. In addition, a potential of NDE for the hardness of deformed low carbon steel using the impedance measurement was confirmed experimentally.