Use of Time-Frequency Representation of Magnetic Barkhausen Noise for Evaluation of Easy Magnetization Axis of Grain-Oriented Steel

Abstract

The paper presents a new approach to non-destructive evaluation of easy/hard magnetization axis in grain-oriented SiFe electrical steels based on the Barkhausen phenomenon and its time-frequency (TF) characteristics. Anisotropy in steels is influenced by a number of factors that formulate the global relationship and affect the Barkhausen effect. Due to the observed high variability in the dynamics of magnetic Barkhausen noise (MBN) over time, obtained for various directions in grain-oriented steel, it becomes justified to conduct MBN signal analyses in the time-frequency domain. This representation allows not only global information from MBN signal over entire period to be expressed, but also detailed relationships between properties in time and in frequency to be observed as well. This creates the opportunity to supplement the information obtained. The main aspect considered in the work is to present a procedure that allows an assessment of the resultant angular characteristics in steel. For this purpose, a sample of a conventional grain-oriented SiFe sheet was used. Measurements were made for several angular settings towards the rolling and transverse directions. A data transformation procedure based on short-time Fourier transform (STFT) as well as quantitative analysis and synthesis of information contained in the TF space was presented. Angular characteristics of selected TF parameters were shown and discussed. In addition, an analysis of the repeatability of information obtained using the proposed procedure under various measurement conditions was carried out. The relationship between the selection of calculation parameters used during transformation and the repeatability of the obtained TF distributions were demonstrated. Then the selection of the final values of the calculation parameters was commented upon. Finally, the conclusions of the work carried out were discussed.

Analysis of the Possibility of Using Various Time-Frequency Transformation Methods to Barkhausen Noise Characterization for the Need of Magnetic Anisotropy Evaluation in Steels

“…In contrast, the direction of hard magnetization requires the use of higher field values for the same purpose. Barkhausen Noise is one of the methods that can be used to characterize anisotropic properties, as the noise activity and the dynamics of the MBN phenomenon are strictly dependent on the direction of the magnetizing field with respect to the rolling axis [20,21,[25][26][27]. Before the measurements, no additional treatment was made to the material.…”

“…the MBN phenomenon are strictly dependent on the direction of the m with respect to the rolling axis [20,21,[25][26][27]. Before the measurements, no ment was made to the material.…”

“…The excitation current was 370 mA, which corresponds to the value of approximately 1.6 kA/m of magnetizing field. A detailed description of the transducer and measuring system can be found in [19][20][21]28]. Before the data acquisition process, the signal was filtered using analog filters with the pass band set to the 2 kHz-100 kHz range.…”

“…The analysis provides information on changes in MBN activity in specific time periods of the magnetization process for different directions of the magnetic field, which may be helpful in explaining the source of the resultant anisotropy characteristic in ferromagnetic materials. In paper [21], the determination of easy and hard magnetization axes were presented by analyzing the MBN signals using the STFT transform. The influence of the measuring condition on the quality of information on magnetic anisotropy was also analyzed by the authors.…”

Analysis of the Possibility of Plastic Deformation Characterisation in X2CrNi18-9 Steel Using Measurements of Electromagnetic Parameters

“…A synthetic description of the theoretical basis related to this article is included in [ 16 ], where an analysis was conducted of the possibility of assessing active stresses in steel elements by measuring electromagnetic diagnostic signals. Many articles were referred to in [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], where information can be found on the theoretical basis of the applied electromagnetic methods.…”