Distortion analysis of magnetic excitation-a novel approach for the non-destructive microstructural evaluation of ferromagnetic steel

摘要

The presence of a different ferromagnetic material, between the poles of a U-shaped iron-cored electromagnetic (EM) yoke, has been observed to introduce a distortion in the alternating excitation voltage (V_E) across the coil around the EM yoke. The influence of four different microstructural conditions of a ferromagnetic 18CrNiMo5 gear steel on the distortion behaviour of the magnetic excitation voltage has been investigated. The time derivative of the excitation voltage (dV_E/dt) plotted as a function of total applied voltage (V_T) has been found to show a unique shape for each sample with different microstructural conditions. The systematic changes in the height and position of the peak and the trough on the voltage-time derivative profile reflect the difference in the magnetization process for each microstructural condition. This study reveals the good potential of this simple method of distortion analysis of magnetic excitation for a variety of applications related to material evaluation of ferromagnetic steel components.