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.