Improvement in the Equivalent Indirect Hysteresis Cycles Obtained From the Distortion of the Voltage Measured in the Excitation Coil

The equivalent indirect hysteresis cycle ( $B_{\mathrm {ec}}$ – $H$ cycle) obtained from the distortion of the voltage measured in the excitation coil facilitates the implementation of magnetic nondestructive characterization systems reducing hardware and error sources, as pick-up coils and their conditioning stages are not necessary. The aim of this article is to propose a sine-fitting (SF) algorithm in order to obtain the $B_{\mathrm {ec}}$ – $H$ cycles for nondestructive testing applications. Although the parameters of $B_{\mathrm {ec}}$ – $H$ cycles are not an accurate measurement of magnetic properties, they are equivalent to those of the indirect hysteresis cycles and thus are sensitive to different material processing variables. The $B_{\mathrm {ec}}$ – $H$ cycles of low carbon, dual phase, and ultrahigh strength steels obtained using SF and synchronous demodulation (SD) algorithms are compared. The parameters of $B_{\mathrm {ec}}$ – $H$ cycles obtained using the SF algorithm evidence greater sensitivity to material processing variables and are linearly correlated with parameters of indirect hysteresis cycles.