부산대학교 도서관

A new method is developed to measure reversible permeability as a function of frequency and bias field for application to modeling of magnetostrictive electromagnetic acoustic transducer; these transducers are used for ultrasonic nondestructive evaluation of magnetic materials. The method is based on a new model developed to predict the impedance of a rectangular eddy current coil when placed in proximity to a ferromagnetic specimen; inputs to this model are geometry of the coil, frequency, permeability, and conductivity of the specimen. This method was applied to a specimen of SAE1018 carbon steel. Experimental measurements of the specimen impedance, combined with the new theoretical model, enabled the reversible permeability to be determined in the presence of bias field levels ranging from 0 to 46 000 A/m and frequencies ranging from 350 kHz to 1.1 MHz. Frequency and bias field dependence of reversible permeability for this specimen is consistent with a model of magnetic domain rotation and wall movement. [ABSTRACT FROM AUTHOR]