Magnetic Barkhausen Noise Energy Research Articles

Evaluation of the wear mechanism of ferromagnetic materials based on magnetic barkhausen noise

ABSTRACT As a typical form of damage, wear greatly affects the service properties of products, and non-destructive evaluation of the degree of wear is urgently needed. In this paper, the wear degree of AISI 1045 steel was evaluated by magnetic Barkhausen noise (MBN) testing. The root mean square (RMS) and full width at half maximum (FWHM) of MBN were extracted to establish the quantitative relationships between the tribological indicators and the stress state. The results indicate that the RMS decreases linearly and the FWHM increases quadratically with increasing tribological indicators, which can distinguish among different wear stages, including abrasive, adhesive and fatigue wear. However, the RMS shows a complicated nonlinear relation with the residual stress during the wear process. In addition, the MBN energy parameter is also calculated to reveal the features of the hysteresis loop at the wear scar. Both the coercivity H c and the maximum magnetic permeability μ max are linearly related to the tribological indicators and quadratically related to the stress, which reflects the effect of tribo-magnetisation on the MBN signals. The variation mechanism of MBN under different wear stages is attributed to the combined effect of plastic deformation and the stress state by microstructure observations.

Barkhausen noise hysteresis cycle: Theoretical and experimental understanding

Magnetic Barkhausen Noise (MBN) reflects magnetic domains’ motions during a ferromagnetic part’s magnetization process. For industrial specimens, the raw MBN signal is stochastic and not reproducible, leading to complex analyses. This issue is solved using time-average variables like the Magnetic Barkhausen Noise energy (MBNenergy).Plotting MBNenergy as a function of the magnetic excitation gives rise to a hysteresis cycle. Recent studies have highlighted some exciting properties from this cycle, such as a way to observe the magnetic loss contribution associated with the domain wall motions. Still, questions remain, including in the basic description of MBNenergy.This paper describes a theoretical development to understand MBNenergy further. We demonstrate that in standard characterization conditions, the magnetization variations associated with the domain wall motions are proportional to the square of the envelope of the MBN signal instead of its absolute value.Then, this theoretical conclusion is confirmed experimentally. Finally, the absence of privileged orientation and direction in the MBN effect is verified in the case of unidirectional magnetization.

Temper embrittlement in HY-80 steel: Microstructure, magnetic and microhardness properties

Temper embrittlement is characterized by the migration of impurity elements and carbides towards the grain boundaries of alloy steels, such as HY-80 steel. The accumulation of inclusions at grain boundaries causes dramatic reductions in impact toughness due to the increased susceptibility of intergranular fracture. This kind of failure can be catastrophic for submarines under high pressure with hulls constructed of HY-80 steel. The detection of temper embrittlement is crucial for the safety of the crew. Currently, the most common method of detecting temper embrittlement is destructive, which is costly and inefficient. Non-destructive methods of temper embrittlement detection are more desirable, however, there are no widespread methods currently in use. One possible non-destructive method utilizes Magnetic Barkhausen Noise (MBN). This method was investigated by testing eight HY-80 samples for MBN energy, microhardness, and microstructural changes before and after a heat treatment at 525 °C for a variety of holding times. Scanning electron microscopy showed carbide migration to the grain boundary and spheroidization with increased holding time. Microstructural quantification was performed using computer vision to extract useful data on precipitate behavior during heat treatment. The microhardness of each sample was measured using Vickers microhardness testing before and after heat treatment to further characterize the level of temper embrittlement. Microhardness changes with holding time were attributed to the change in precipitate density and the migration of the precipitates to the grain boundary during temper embrittlement.

Effect of stress on the magnetic Barkhausen noise energy cycles: A route for stress evaluation in ferromagnetic materials

The analysis of the magnetic Barkhausen noise energy hysteresis cycles, MBNenergy(H), is a promising non-destructive testing method for evaluating internal mechanical stresses in ferromagnetic structural steels. This study applies this method to two ferromagnetic materials with significantly different behaviors subjected to uniaxial tensile stress. Coercivity is shown to be the most sensitive tensile stress indicator. A multiscale model is then developed to simulate the stress-dependent MBNenergy(H) anhysteretic behavior. Combined with a hysteresis contribution, it successfully reproduces the whole cycle. 2D simulation predictions reveal that the identification of uniaxial tensile stress is more efficient when the magnetic field is applied with an angle between 30° and 75° from the stress direction. The proposed modeling approach allows the prior determination of the most favorable configurations for the sensor orientation depending on the material tested and all available a priori knowledge of the stress configuration.

Construction of Energy Loops Using Magnetic Barkhausen Noise

Magnetic Barkhausen Noise (MBN), which contains microstructure information of materials, is widely used in Non-Destructive Testing (NDT) of magnetic materials. The magnetic Barkhausen noise energy (<i>MBN</i>_energy) is one of the time-independent indicators for NDT, but the initial <i>MBN</i>_energy has no clear physical meaning and cannot be used to explain the relationship with the hysteresis loop. In this paper, based on the physical mechanism of MBN, the proportional relation is built between MBN voltage signal <i>V</i>_B and energy loss, and then relate it with the energy loss through wall pinning of J-A hysteresis model. We define a novel magnetic Barkhausen noise energy eigenvalue (<i>MBNE)</i> as the time integral of the product of the absolute value of <i>V</i>_B and the sign function sign(d<i>H</i>&#x002F;d<i>t</i>). We have proved that the <i>MBNE</i> is proportional to the irreversible magnetization <i>M</i>_irr. Since <i>M</i>_irr is equal to the saturation magnetization <i>M</i>_s when the magnetization of ferromagnetic material reaches saturation, we scale the <i>MBNE</i> to make its maximum value equal to <i>M</i>_s, and find that the relationship curve <i>MBNE</i>(<i>H</i>) of <i>MBNE</i> with respect to the magnetic field <i>H</i> coincides with the irreversible hysteresis loop <i>M</i>_irr(<i>H</i>). We call the <i>MBNE</i>(<i>H</i>) as the magnetic Barkhausen noise energy loop. Then, the <i>MBNE</i>(<i>H</i>) and <i>M</i>_irr(<i>H</i>) of two kinds of electrical steel sheets are compared by experimental results, which validates the adaptability of the <i>MBNE</i>(<i>H</i>) construction method. The method to obtain <i>M</i>_irr(H) from the MBN raw signal revels the physical mechanism of MBN and the irreversible magnetization process of magnetic material.

Angular magnetic Barkhausen noise of incline- and cross-rolled non-oriented electrical steel sheets

Magnetic Barkhausen noise (MBN) analysis is a relatively new technique used to characterize the magnetic properties of electrical steels. Not only has it been utilized to evaluate the overall core loss of electrical steel sheets, but it has also been employed as a non-destructive testing (NDT) tool to assess the magnetocrystalline anisotropy of ferromagnetic materials. In this study, non-oriented electrical steel sheets produced by inclined and cross rolling were characterized by both MBN and electron backscatter diffraction (EBSD). The angular MBN measured on the surface of the steel sheet was directly compared to the magnetocrystalline anisotropy energy (MAE) calculated from the measured crystallographic texture. The MBN energy corresponding to the saturation-to-remanence part of the hysteresis loop was evaluated, which had been reported to have a close correlation to the MAE in pipeline steels. The results in this study showed that such a relationship did not exist in any of the electrical steel samples examined (including deformed, partially recrystallized, and completely recrystallized), although in some samples the polarities of the MBN and MAE partially coincide. It was shown that the residual stress in the material played an important role in determining the polarities of the angular MBN, which had been ignored in the previous studies when comparing the MBN to the MAE. Possible reasons that caused the discrepancies between the results of this study and those of the previous studies were given.

Evaluation of the stress gradient of the superficial layer in ferromagnetic components based on sub-band energy of magnetic Barkhausen noise

ABSTRACT Since magnetic Barkhausen noise is very sensitive to the change of the stress or residual stress level in components, it is feasible to detect the stress or residual stress profile along the depth direction by the magnetic Barkhausen noise method. An engineering approach was used to validate a theoretical model describing the relationship between magnetic Barkhausen noise and stress magnitude. To generate stress gradients in the specimen of Q235 steel under different deflections, the four-point bending device was used. Then the detected signals obtained in the experiment were divided into different sub-bands to evaluate the stress at different depths. The testing depth was set to be around 100 μm due to the rapid exponential attenuation of the noise signals. In the experiments, the sub-band energy density showed sensitive as the loading displacement increasing. The experimental results showed that the signal energy was also sensitive to the plastic deformation of the material. Within the depth of 100 μm, the stress change was very small. The final experimental results showed that even under such small stress variations, it is sensitive and feasible to use the magnetic Barkhausen noise energy to characterise the change of stress gradients.

Magnetic Barkhausen Noise Testing for Subsurface Discontinuities under DC Magnetization

Subsurface discontinuities are inevitably formed during the long-term operations of pipelines, oil tanks, ship hulls, and the like. However, it is still a big challenge to detect deeply buried subsurface discontinuities using existing nondestructive testing methods. In this paper, based on the high sensitivity of magnetic Barkhausen noise (MBN) to the movement of the domain walls, an MBN test under direct current (DC) magnetization is proposed for subsurface discontinuity detection. Under DC magnetization, subsurface discontinuities will distort the magnetic field distribution in the near-surface layer of the specimen and then affect the movement of the domain walls in this region. Meanwhile, through alternating current (AC) excitation, MBN testing is conducted to detect the movement of the domain walls to evaluate subsurface discontinuities. To validate the proposed technique, MBN experiments under DC magnetization are conducted to quantify subsurface discontinuities with different buried depths. Experimental results indicate that the proposed technique can detect subsurface discontinuities with buried depths of up to 5 mm, and the extracted MBN energy feature has an approximately linear relationship with the buried depth.

Multiscale modelling of the magnetic Barkhausen noise energy cycles

The magnetic Barkhausen noise (MBN) control is popular for materials characterization and as a magnetic Non-Destructive Testing & Evaluation (NDT & E) method. MBN comes from the erratic and unpredictable magnetic domains motion during the magnetization process. Its correlation to the micro-structural properties is evident. MBN is usually studied through time independent indicators, like the MBNenergy, which is obtained by integrating the square of the MBN voltage signal with respect to the time axis. By plotting the MBN energy as a function of the tangent excitation field H, a hysteresis cycle can be observed. After renormalization, the comparison with the classic induction vs excitation B(H) hysteresis loop provides interesting observations. Similar shapes can be observed if the domain wall contribution is preponderant in the magnetization process. On the contrary, strong differences appear if the magnetization rotation mechanism is stronger. There is no available standard for the exploitation of MBN control devices. Usual procedures rely on rejection thresholds based on empirical relations. In this domain, simulation tools able to refine these thresholds and improve the understanding of the physical behavior are highly desired. In this study, a simulation method combining a multiscale model for the anhysteretic behavior and the Jiles-Atherton theory is proposed to simulate precisely the MBNenergy hysteresis cycles. The use of the multiscale model allows separating the contributions of domain wall motion and magnetization rotation mechanisms. The satisfying simulation results validate the approach and constitute a major step toward a comprehensive simulation tool dedicated to MBN.

Magnetic Barkhausen Noise Measurements to Assess Temper Embrittlement in HY-80 Steels

Magnetic Barkhausen noise (MBN) can result from abrupt motion of domain walls due to their interaction with pinning sites during magnetization of ferromagnetic steel. However, understanding domain structure interactions with pinning site density is limited. In this article, the effect of density of pinning sites within grains of HY80 steel, on generation of MBN, was investigated. Pinning site density was modified by a heat treatment that produces temper embrittlement. Temper embrittlement refers to the reduction of fracture toughness of alloy steels when heated or slowly cooled through the embrittling temperature range and arises due to migration of impurity elements to grain boundaries. Samples, machined from a casting, were held at a constant temperature (525 °C) for different holding times, to generate varying degrees of temper embrittlement. MBN signal response was observed to decrease exponentially as a function of holding time with decay constants (relaxation time) in the range of 160-190 h. A reduction in the MBN signal along each sample's easy axis was attributed to different densities of impurity elements, which act as pinning sites for domain wall movement within grains. Samples were also characterized using a scanning electron microscope (SEM), hardness testing, and impact toughness testing. Hardness was observed to increase with holding time and MBN energy decreased linearly with increasing hardness. Furthermore, a linear relationship between impact energy and MBN energy was observed. This implies that MBN signal analysis can be used as an indirect measure of the change in material properties of the sample.

Non-destructive testing on creep degraded 12% Cr-Mo-W-V ferritic test samples using Barkhausen noise

Micro-magnetic non-destructive testing helps in evaluating the mechanical and structural integrity of ferromagnetic components (mostly steel) via local magnetic characterization. As a means of revealing the magnetic domain wall movements, the Barkhausen noise measurement method is a micro-magnetic non-destructive testing method of considerable potential and interest. The Magnetic Barkhausen Noise Energy (MBNenergy) method can be used to reconstruct local hysteresis cycles from Barkhausen noise measurements. These cycles constitute good indicators for understanding the magnetization process and the influence of microstructural and mechanical properties. In this article, the MBNenergy method is employed for evaluating the microstructural changes induced by creep/ageing of high chromium steel subjected to different creep test conditions as stress and temperature. The corresponding magnetic parameters are investigated in relation to precipitations and dislocations. After the experimental analysis, simulations are performed based on the Jiles-Atherton theory for the quasi-static magnetic behavior. This simulation approach yields physically meaningful model parameters that can be analyzed and linked to the sample microstructural characteristics, thereby enabling physical interpretation.

Magnetic Barkhausen Noise Characterization of the Recrystallization of a Non-Oriented Electrical Steel after Cold Rolling at Different Angles to the Hot Rolling Direction

Non-oriented electrical steel sheets are the most commonly used material for the manufacturing of magnetic cores for electric motors and generators. The microstructure and texture of the steel after final annealing have a significant effect on the magnetic properties of the lamination core. To investigate the effect of cold rolling and annealing on the magnetic properties of the steel sheets, a 0.9 wt% Si non-oriented electrical steel was cold rolled at different angles to the hot rolling direction (HRD) and annealed at various temperatures (600°C to 750°C) to produce dissimilar microstructures. The progress of recrystallization was characterized by electron backscatter diffraction (EBSD), and the magnetic response of the steel at various stages of recrystallization was evaluated by magnetic Barkhausen noise (MBN). A number of MBN parameters, e.g. the root mean square, the smoothed envelope, the peak, the full width at half maximum (FWHM) of the envelope, the time integral of the MBN signals and the MBN energy, were analyzed with respect to the fraction of recrystallization during annealing. The results show that cold rolling at different angles to the hot rolling direction induces various deformation microstructures and stored energies, which, in turn, lead to considerably different recrystallization behaviours during annealing. The difference in recrystallization of these materials is also reflected in the MBN parameters.

Characterization and modeling of magnetic domain wall dynamics using reconstituted hysteresis loops from Barkhausen noise

By means of a post-processing technique, we succeeded in plotting magnetic Barkhausen noise energy hysteresis cycles MBNenergy(H). These cycles were compared to the usual hysteresis cycles, displaying the evolution of the magnetic induction field B versus the magnetic excitation H. The divergence between these comparisons as the excitation frequency was increased gave rise to the conclusion that there was a difference in the dynamics of the induction field and of the MBNenergy related to the domain wall movements. Indeed, for the MBNenergy hysteresis cycle, merely the domain wall movements were involved. On the other hand, for the usual B(H) cycle, two dynamic contributions were observed: domain wall movements and diffusion of the magnetic field excitation. From a simulation point of view, it was demonstrated that over a large frequency bandwidth a correct dynamic behavior of the domain wall movement MBNenergy(H) cycle could be taken into account using first-order derivation whereas fractional orders were required for the B(H) cycles. The present article also gives a detailed description of how to use the developed process to obtain the MBNenergy(H) hysteresis cycle as well as its evolution as the frequency increases. Moreover, this article provides an interesting explanation of the separation of magnetic loss contributions through a magnetic sample: a wall movement contribution varying according to first-order dynamics and a diffusion contribution which in a lump model can be taken into account using fractional order dynamics.

Influence of the maximum applied magnetic field on the angular dependence of Magnetic Barkhausen Noise in API5L steels

This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements.

Identification of different processes in magnetization dynamics of API steels using magnetic Barkhausen noise

This work presents a method to identify processes in magnetization dynamics using the angular dependence of the magnetic Barkhausen noise. The analysis reveals that three different processes of the magnetization dynamics could be identified using the angular dependence of the magnetic Barkhausen noise energy. The first process is the reversed domain nucleation which is related to the magneto-crystalline energy of the material, and the second and third ones are associated with 180° and 90° domain walls motions, respectively. Additionally, two transition regions were identified and they are located between the regions associated with the aforementioned processes. The causes involving these processes are analyzed and a method for establishing their location in the Barkhausen noise signal with respect to the applied magnetic field intensity is proposed.

Local Magnetic Properties in Non-oriented Electrical Steel and Their Dependence on Magnetic Easy Axis and Misorientation Parameters

Abstract An understanding of how material parameters, especially orientation and misorientation, influence the magnetic properties of non-oriented electrical steel (NOES) is important for improving the efficiency of the material in service. In this study, the local magnetic properties were measured using magnetic Barkhausen noise (MBN) on different test locations on different strips of NOES material. Local variations in magnetic properties, texture, and misorientation were revealed. A new interpretation for misorientation, called the easy axis misorientation (EAM), was created to describe the alignment of the magnetic easy axes between neighboring grains. This new EAM, visualized as a single value parameter or graphed as a distribution, was shown to be more effective at predicting the isotropic magnetic properties than previously used texture parameters based on standard orientation/misorientation definitions. It was found that a larger EAM value, especially when associated with a lower small angle EAM intensity distribution, was associated with a larger MBN energy. A larger MBN energy has been previously associated with lower losses, and therefore a greater material efficiency.

Magnetic Barkhausen Noise for Characterization of Recovery and Recrystallization

The capacity of magnetic Barkhausen noise (MBN) measurements to characterize recovery and the onset and evolution of recrystallization processes occurring during the annealing of cold rolled low carbon steel is analyzed. Cold rolled low carbon steel samples were isothermally annealed at laboratory under different conditions in order to promote various degrees of recovery or recrystallization. The effect of recovery and recrystallization processes on the MBN envelope, the amplitude of the peak of the MBN envelope, the time integral of the MBN envelope and the MBN energy is discussed and related to the microstructural changes produced by these softening processes. The obtained results prove that several parameters derived from the MBN are able to follow the progress of recovery and recrystallization.

Effect of anisotropic microstructure on magnetic Barkhausen noise in cold rolled low carbon steel

We have measured the orientation and depth dependence of the magnetic Barkhausen noise (MBN) in an industrial pipeline steel sheet. Thin samples were cut out from the sheet cross section at different depths, parallel and transverse to the rolling direction (rolling and transverse samples). The integrated MBN energy has shown no depth dependence for transverse samples. On the other hand, the rolling samples have shown larger MBN noise energy and strong depth dependence. The microstructure of the samples was studied by optical and electron microscopy, parameters related to the shape and the quantity of carbon precipitates and grains were extracted by image processing techniques. The strong depth and orientation dependence of the MBN have been explained by changes of the grain and precipitate microstructure.

Effect of Microstructure Changes on Barkhausen Noise Properties and Hysteresis Loop in Cold Rolled Low Carbon Steel

Low carbon steel specimens cold rolled at ratios of 0-40% have been examined comprehensively by means of magnetic Barkhausen noise (MBN) method and a physical parameter obtained from a hysteresis loop, and their microstructures were studied by a transmission electron microscope. The behaviors of MBN and coercive force with reduction ratio were discussed in relation to microstructure changes. The MBN energy rises rapidly with cold rolling below 10% reduction, and saturates at higher reduction ratio. The peak in averaged rms voltage exhibited the same behavior as that of the MBN energy, whereas the coercive force and the magnetizing current when the averaged rms showed a peak increased monotonically with increasing reduction ratio. These phenomena are attributed to the combined effects of cell texture and dislocation density.

Analysis of the stress dependent magnetic easy axis in ASTM 36 steel by the magnetic Barkhausen noise

The angular distribution of the magnetic Barkhausen noise energy is used to determine the influence of the applied stress in cold rolled ASTM 36 steel. In particular, the magnetic easy axis is predicted by the angular distribution of the magnetic Barkhausen noise energy, which, in turn, is obtained by magnetizing the samples in the radial direction from the center of the sample. The results indicate that the applied uniaxial stress gives origin to a continuous rotation of the magnetic easy axis. In addition, this study reveals that the jump energy distribution presents a clear angular dependence and is very sensitive to the anisotropic behavior of the magnetic Barkhausen noise activity.