Magnetically Induced Potential Noise (MIPN)—A New Method for the Characterization of Magnetic Materials and for New Sensor Applications

This paper discusses a new methodology for characterizing the magnetic properties of ferromagnetic materials. The method uses an alternating electric current to periodically magnetize ferromagnetic materials. The periodic magnetization generates a high-frequency electric potential noise between two electrodes within the excitation circuit. The magnetically induced electric potential noise (MIPN) is related to the discontinuous processes that occur during magnetization similar to magnetic Barkhausen noise. This paper discusses the results of several experiments that measured both electric potential noise and Barkhausen noise signal. A comparison of the results showed that the MIPN correlates directly to magnetic Barkhausen noise. The MIPN signal is small when compared to Barkhausen noise, but it is still easy to measure under laboratory conditions. Therefore, MIPN could be an efficient technique for materials characterization and sensor technology, for example, as fiber stress sensors in a composite aircraft component.     

Magnetically Induced Potential Noise (MIPN)—A New Method for the Characterization of Magnetic Materials and for New Sensor Applications

Abstract

This paper discusses a new methodology for characterizing the magnetic properties of ferromagnetic materials. The method uses an alternating electric current to periodically magnetize ferromagnetic materials. The periodic magnetization generates a high-frequency electric potential noise between two electrodes within the excitation circuit. The magnetically induced electric potential noise (MIPN) is related to the discontinuous processes that occur during magnetization similar to magnetic Barkhausen noise. This paper discusses the results of several experiments that measured both electric potential noise and Barkhausen noise signal. A comparison of the results showed that the MIPN correlates directly to magnetic Barkhausen noise. The MIPN signal is small when compared to Barkhausen noise, but it is still easy to measure under laboratory conditions. Therefore, MIPN could be an efficient technique for materials characterization and sensor technology, for example, as fiber stress sensors in a composite aircraft component.     

磁巴克豪森噪声检测材料疲劳的励磁频率优化研究

磁巴克豪森噪声在铁磁性材料早期疲劳损伤的检测中具有巨大的应用潜力.在疲劳检测过程中,励磁频率作为磁巴克豪森噪声的激发源,对检测结果有重要影响.实验研究励磁频率对磁巴克豪森噪声检测铁磁性材料疲劳时检测结果的影响规律,以20R钢材料为对象进行低周疲劳实验,并在励磁频率分别为9,16,35,60?Hz下对取自同一母材的3个试...     

Nondestructive evaluation of ferromagnetic materials by a “magnetometer like” experimental arrangement

The paper presents experimental results regarding the influence of mechanical stresses and thermal treatments on the Barkhausen noise and magnetization characteristic of MolyPermalloy and MuMetal ferromagnetic samples. The samples are different in stress magnitude and localization and in their thermal history. The level of Barkhausen noise and the changes in magnetization characteristic are estimated by measuring the sensitivity and transduction gain of magnetometer like coils configurations which employ the studied ferromagnetic samples as their nonlinear ferromagnetic cores. The present method is unique in the sense that the two factors (one factor is related to the internal magnetic noise, and the other one is related to the form of the magnetic characteristic) are obtained by employing a single relatively simple experimental arrangement. Various types of stresses, which are different in magnitude and localization, become distinguishable one from the other, when considering their differential effects on the two factors. Several possible experimental arrangements are shown.     

Robust estimation of magnetic Barkhausen noise based on a numerical approach

This paper deals with a multifeature numerical instrument for nondestructive testing of ferromagnetic materials, based on the Barkhausen noise. Starting from traditional instruments based on the root mean square value of the band-pass filtered measured signal, the proposed method is based on the simultaneous analysis of the excitation voltage, the excitation current, and the induced signal. A good repeatability improvement is achieved by monitoring the excitation impedance, while synchronizing the rms evaluation to the excitation current signal increases the robustness with respect to the environmental electromagnetic noise. Moreover, experimental results encourage the use of shape-based features to better characterize the Barkhausen signal.     

Correlation Between AC Core Loss and Surface Magnetic Barkhausen Noise in Electric Motor Steel

Core loss is a significant source of energy loss in electric motor steel laminates. Therefore, there is interest in monitoring the quality and consistency of laminates at various stages of manufacturing. The purpose of this study was to investigate the feasibility of using surface magnetic Barkhausen noise for the evaluation of AC core loss, and further, to examine potential origins of magnetic loss in non-oriented electrical steel. Core loss values were measured by a single sheet tester and Barkhausen noise measurements were performed using pole flux control on eight laminates with various grain size, texture and composition. Magnetocrystalline energy was calculated from X-ray diffraction data to quantify texture. Results demonstrated higher surface Barkhausen emissions for samples with lower core loss. Barkhausen noise analyses were used to examine the interplay among core loss, grain size, magnetocrystalline energy and B–H characteristics. The inverse correlation between core loss and Barkhausen noise emissions was qualitatively explained in terms of the orthogonal vector contribution of microscopic eddy currents to losses associated with bulk currents arising in the sample during magnetization.     

Multi-parameter Evaluation of Magnetic Barkhausen Noise in Carbon Steel

The sensitivity of magnetic Barkhausen noise to many factors has limited its potential application for basic material characterization and detection of residual stress in carbon steel, a common structural material. The present work investigates Barkhausen noise response in plain carbon steel under conditions of varying carbon content, applied elastic stress and different magnetization level. The surface Barkhausen noise measurement system uses a feedback for controlling the flux waveform, which facilitates reproducibility of measurements and also permits extraction of additional parameters from the B–H loop of magnetic circuit. Barkhausen noise parameters correlate with known material parameters, such as coercivity, which vary with carbon content and stress. These results demonstrate the potential for in-situ characterization of carbon steel.     

Characterization of strain-induced martensitic transformation in A301 stainless steel by Barkhausen noise measurement

Kinetics of strain-induced martensitic transformation under biaxial stress state in metastable austenitic AISI 301 stainless steel was characterized by electron back-scattered diffraction and Barkhausen noise measurement. The effect of martensite volume fraction, degree of plastic strain, crystallographic texture and stress state on magnetic properties was evaluated. Increase in Barkhausen noise signal is related both to an increase in the magnetic domains volume fraction due to a transformation of non-magnetic austenite to magnetic martensite and to a reorientation of magnetic domains into 〈1 0 0〉 direction. Up to the saturation of martensite volume fraction, Barkhausen noise is affected by newly created martensite, and subsequently by plastic strain. The intensity of Barkhausen noise signal is strongly angle-dependent as the easy magnetization axis is developed in the transverse direction of pre-strained sheets.     

Magnetic Barkhausen emission study in heat-treated Fe-Nb-Cu-Si-B alloy

Magnetic hysteresis and magnetic Barkhausen emission (MBE) parameters have been studied for as-received and annealed Fe/sub 72/Nb/sub 4.5/Cu/sub 1/Si/sub 13.5/B/sub 9/ alloys. The coercivity rapidly decreased at the initial stage of annealing, in contrast to the slow change of root-mean-square voltage of Barkhausen emissions. The amplitude of the Barkhausen emission signal reduced almost to the background noise level at an intermediate annealing temperature, at which the material exhibited superior soft magnetic properties. Pulse height distribution of the MBE signal showed the existence of a large number of small amplitude pulses at the intermediate range of annealing, an indication that the magnetization process of the system is dominated by the rotation of the magnetization vector within a small volume of nanocrystalline particles. We explain the results by a random anisotropy model, assuming the exchange coupling between the Fe/sub 80/Si/sub 20/ nanograins of higher magnetic moment takes place through the magnetically weaker amorphous matrix.     

Stress Response of Magnetic Barkhausen Noise in Submarine Hull Steel: A Comparative Study

The development of magnetic Barkhausen noise methods for rapid detection of residual stress concentrations has implications for integrity assessment of submarine pressure hulls. However, the stress-response of Barkhausen noise in submarine hull steel, HY-80, is complicated by the influence of the material’s martensitic microstructure. The present work sheds light on the stress-dependent behavior of Barkhausen noise in HY-80 by comparing its signal characteristics with those of more common ferrite/pearlite steels. HY-80 and various ferrite/pearlite steel plates were uni-axially stressed up to and beyond the level for plastic deformation. Barkhausen noise measurements, performed using the same sensor under reproducible flux-controlled magnetization conditions, facilitated a direct comparison of material responses. Results showed that with the application of tensile stress, the Barkhausen noise signal of ferrite/pearlite steels linearly increased, reached a peak value and saturated in the elastic region. By contrast, HY-80 demonstrated a linear increase with tensile stress characterized by a transition from a lower to a seven times higher rate of change for stresses above 200 MPa up to its yield point. The different stress-response of HY-80 was attributed to its martensitic microstructure, which modifies the response of the domain structure under tensile stress conditions.