Evaluation of Barkhausen Noise and Magnetoacoustic Emission Signals Properties for Plastically Deformed Armco Iron

Abstract

The paper presents the results of the investigation of the influence of different modes of plastic deformation on the magnetoacoustic properties of Armco iron. Two sets of samples have been investigated-the first one consisted of preannealed samples that had been subsequently cold rolled, and the second one consisted of samples cut out from commercially available Armco plates, subjected to tensile loading. The process of cold rolling leads to the broadening of the envelopes and to the appearance of the third central peak [attributed to the domain-wall (DW) pinning]. In the case of the nonannealed samples, the Barkhausen envelope for the as-received sample reveals one, broad maximum that is transformed by the following tensile deformation initially into two and then three peaks. In order to detect subtle changes of the Barkhausen noise (BN) properties, a multiparameter [fast Fourier transform (FFT), pulse height distribution, wavelet transform] analysis was performed. As for the magnetoacoustic emission (MAE) signal, both deformation modes result in visible increase in peak separation as well as in the increase of the MAE intensity. As for the peak separation, it can be understood as the result of both the increase of the coercivity of the samples and the decrease of the slope of the B(H) loops since the MAE signal is generated mainly during creation/annihilation of DW occurring mainly at the knee regions of the B(H) loops.