Comparison of AC and pulsed magnetization-based elasto-magnetic methods for tensile force measurement in steel strand

Abstract

AC and pulsed magnetization-based elasto-magnetic measurement methods of tensile force in steel strand are compared in the study. Completely opposite conclusions on the dependency of maximum magnetic induction on the tensile force are drawn from the two modes. The opposite conclusions are consistent with the predicted results before and after the Villari reversal point. Harmonic and spectral analysis techniques are introduced to investigate new feature parameters for tensile force characterization. In AC mode, the distortion factor of the induced voltage signals demonstrates the better stability and force prediction accuracy than the conventional time-domain feature parameters of maximum magnetic induction and coercive force. In the pulsed mode, the linear correlation between the spectral amplitudes of the induced pulsed signals and the tensile force is analyzed. A new parameter, the summation of the spectrum amplitudes in a particular band, is introduced to characterize tensile force. The calibration curve for tensile force measurement with the new parameter shows a lower prediction error and hysteresis error compared to the time-domain analysis results. Conclusions obtained from the comparative study on the performance of the two magnetization modes and two types of parameters may provide new insights into the improvements in the tensile force detection accuracy of the elasto-magnetic methods.