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Barkhausen pulses (BPs) in ferroelectrics manifest themselves as sharp peaks in switching current during polarization reversal. The total input of BPs in previously studied ferroelectric crystals i...

Nowadays, precision manufacturing industries are required faster surface inspection tools for the achievement of high productivity. In this context, the Barkhausen noise (BN) technique is adopted as a quick response technique in the grinding for qualitative evaluation of surface integrity of AISI D2 tool steel. Present work investigates the effect of eco-friendly coolant, i.e., cryogenic, on surface integrity of ground sample in the plunge grinding mode at different downfeed and compared with dry and wet environments. Surface integrity was assessed in respect of surface roughness, microstructure, and microhardness. Magnetic response of ground surface was reported by Barkhausen noise analyzer in the form of root mean square (rms), peak, and number of pulses. From the outcomes, it was perceived that no significant variations were found in the microstructure and microhardness of the ground surface and subsurface after cryo-grinding owing to lower thermo-mechanical loading. Besides, lower surface roughness was obtained in the case of cryo-grinding because of thermal softening effect. A linear correlation between BN input parameters, i.e., magnetic field intensity and BN responses at different magnetizing frequency could be achieved. Finally, better BN responses, including higher rms, peak, and number of pulses, were found under the cryogenic environment.

This article reviews the ferromagnetic hysteresis, magnetomechanical, and Barkhausen properties of magnetic materials and presents an integrated model to describe these effects and the underlying mechanisms that cause these effects. Hysteretic properties of ferromagnets, such as permeability, coercivity, remanence, and hysteresis loss are known to be sensitive to external factors including applied stress, temperature, and heat treatment, and internal factors like residual strain, microstructure, grain size, and anisotropy and the presence of precipitates of a second phase, such as iron carbide in steels. It thus becomes imperative to characterize the effect of these factors on the hysteresis parameters. Currently, several models such as Preisach, Stoner–Wohlfarth, and Jiles–Atherton are used to describe the magnetic hysteresis of ferromagnetic materials. We review here the quasistatic Jiles–Atherton hysteresis model which describes hysteresis in terms of domain wall motion enabling a connection to be made to the physical response of the magnetic material. This model has been extended to include the magnetomechanical effect and the Barkhausen effect in ferromagnetic materials. Theoretical work presented here provides a conceptual framework linking together these magnetic property measurements with model parameters and to the structure of the material.

Control of the stress-strain state, compressive and tension stresses, accumulated fatigue damage is one of the goals of non-destructive testing. We consider data of current research in the field of eddy current and electromagnetic methods of non-destructive testing aimed at solving the problem of monitoring the accumulated damage in structural steels and alloys. Developments for practical implementation of the coercive force method, the eddy current structurescopy of non-magnetic materials, the method of higher harmonics and remanence-based control, the method of magnetic noise (Barkhausen noise) are considered. The physical foundations of non-destructive testing methods are considered along with their brief comparative analysis. Examples of non-destructive testing of critical units, such as operating oil and gas pipelines, aircraft parts, bearing parts, pressure vessels, crane parts, etc. are given. The possibility of using the eddy current method for control of the austenitic phase of cold rolled austenitic steels (AISI 304, AISI 321, AISI 316) is analyzed. The examples of static and fatigue tests of the samples of various steels and alloys are given: St3, St20, St45, D16T, AMg6, AMg6N, 12Kh18N9T, 08Kh18N9, 40Kh, R91. Metrology issues and the impact of interfering parameters affecting the measurement error are considered. The equipment used for a number of methods is discussed. Conclusions regarding the limits of applicability and limitations of the considered methods are drawn. The review provides links to both the fundamental works in the field of electromagnetic structurescopy and to modern research in this area which is important for the practical implementation of the devices based on electromagnetic and magnetic methods of non-destructive testing.

Steel weld seams are characterized by heterogeneity of their microstructure. Microstructure affects the nature of the distribution, sign and magnitude of residual stresses. In combination with unfavorable factors (low temperature, metal hypoductility and an unsuccessful joint form) residual stresses lead to a decrease of load carrying capacity of a whole structure. In a weld seam residual stresses are distributed in a complex way and can affect the build quality of heavy section welded structures. Monitoring of residual stresses remains a big problem. Residual stresses in welds are often evaluated only by modeling. Unfortunately, all mathematical models describe the stress state of the welded material with low accuracy. Simple quality control, the results of which can be easy interpreted, is necessary. Welded joints made by manual arc welding and by automatic submerged arc welding were investigated. Butt seams of steel sheets of different thickness have been welded. Steel was low-carbon and low-alloyed. It is often used in welded structures for various purposes, including construction, and for pipelines manufacture. The temperature range of welded structures operation is very large – from-70 to 450С. The authors studied the structure of butt weld seams by the Barkhausen noise method, which is interesting as it represents an alternative to the known methods, which characterizes the structure and stress state of material. The relationship between the weld microstructure and magnetic noise is shown. Studies have allowed us to establish the relationship between the structure and magnetic properties and to evaluate the feasibility of applying the Barkhausen noise method to welded structures.

The article presents variations of rms Barkhausen noise envelopes in the medium-carbon steel used in automotive and power industry. The material was subjected to different loading processes: monotonic loading at room temperature, and constant loading at elevated temperature. The first one enforced a plastic deformation, whereas the second one, a creep. The changes of Barkhausen signal were analysed using microstructural observations including X-ray measurements. In the second part of the paper, the magnetic structure and pinning effect were illustrated by means of the Lorentz microscopy.

This paper presents a systematic study of magnetic non-destructive evaluation of corrosion attack in rope wires via Barkhausen noise emission. Reduction of the effective cross-sectional area due to corrosion is a major factor affecting rope wire bearing capacity. To investigate the potential of Barkhausen noise technique for such purpose, wires of variable corrosion extent were measured and the correlation between the corrosion depth and Barkhausen noise parameters was analysed. It was found that Barkhausen noise parameters exhibit very good sensitivity to the variable corrosion depth. However, the evolution of the magnetic parameters saturates when the corrosion depth exceeds 300 μm. Furthermore, it was observed that Barkhausen emission arises from the wire itself as well as from the corroded layer, including a mixture of oxides and non-corroded fragments.

The aim of this research is to propose a normalization principle for the Barkhausen noise response eliminating a dynamic contribution to the basic signal. To achieve this, it is suggested to reduce the rms profile (envelope) of the Barkhausen noise by the square root of the field rate of change, i.e. U rms ( H ) / dH / dt . This derived from our recent findings showing that the total rms intensity of the Barkhausen noise rises as the square root of the magnetizing frequency 〈 U rms 〉 ∝ f mag and that the rms profile of the Barkhausen noise is determined by the field rate of change U rms ( H ) ∼ dH / dt . Validity of the suggested normalization principle has been proved for various iron-based steels starting from harder steels with a high coercive field H c of several kA/m up to a soft electrical steel and a nanocrystalline ribbon with dc H c ≃ 10 - 30 A/m. At low magnetizing frequencies, the proposed normalization fully compensates the envelope differences giving a stable quasi-static peak near H c . The shape of these stabilized peaks demonstrates a strong resemblance to the differential permeability curves obtained from the concurrent measurements of the magnetic hysteresis loops.

Barkhausen noise (BN) generated by the stochastic movements of domain walls is one of the most popular non-destructive testing signal. To measure the property of material, the feature(s) extracted from BN signal has been focused by the existing studies. Although the physical characteristic of several BN features could be proven, many features used in the BN-related works are prone to being interfered by the noise, temperature and other measurement conditions. In this paper, to build a stable and unified representation of BN signal, a novel BN feature extraction and hardness prediction method is proposed. The proposed method includes BN-reconstructed AR model, modified slow feature analysis for fusing different AR-order signal and discriminant incoherent component analysis for the hardness prediction. In the experiment, all potential parameters involved in our method were tested to show the relationship between the parameters and hardness prediction accuracy. Then our proposed method was compared with other component-analysis-based methods and self-defined isolated-feature-based prediction methods. The experimental result implies that our proposed method outperforms other methods, including features generated by component analysis methods and the combination of conventional BN features.

A study of the dielectric properties and the Barkhausen effect in the PMN-PT-based multicomponent ceramics near the morphotropic phase boundaries in electric fields was performed. It is shown that ...

In the present paper, application of data fusion coupled with three electromagnetic nondestructive technologies (magnetic hysteresis loop, Barkhausen noise, and eddy current) has been explored to achieve higher accuracy and reliability of measurements. The ability of the proposed methodology has been evaluated for determining microstructural changes of D2 cold work tool steel during tempering with focus on decomposition of retained austenite and determination of this phase, quantitatively. The proposed data fusion method takes advantage of ordered weighted averaging aggregation operator and fuzzy defined interval to fuse the data produced by different experiments to obtain more accurate and reliable results. The fusion process also uses redundant information produced by applying different mapping functions modeled by neural networks. The results of the experiments revealed that applying data fusion to the outputs obtained from different experiments produces more accurate results compared to the situation that only outputs of one experiment are used.

Magnetic Barkhausen noise (MBN) plays significant roles to describe the dynamic of domain walls (DWs), but an in-depth understanding of the correlation between Barkhausen effect and magnetostrictive effect during magnetization process is still limited. In this study, we investigated MBN signals and the frequency spectra in a high-magnetostrictive Fe30Co70 alloy wire (λs = 102 ppm) by evaluating the stress effects on MBN profiles at the stress range of 0–150 MPa using tensile test machine. The results from MBN profiles revealed that MBN in the high magnetic field region was responsible for the localized changes of magnetic flux density, dB/dt induced by magnetic distortion related to non-180° DWs or the magnetization rotation. In MBN spectra, the peak shift towards lower frequencies with the increase of stress indicates that the rough pulse-like MBN outbreaks increase, and it results mainly from the increase of DW jumping length which is caused by the pinning effect at grain boundaries where DW energy is relatively high. In addition, stress dependence of the root mean square (RMS) value of MBN showed a good sensitivity (0.038 mV/MPa). Overall, these findings indicate that new MBN measurement system utilizing magnetostrictive materials can be helpful for a wide range of applications such as mechanical stress sensors and energy harvester systems.

In the present work a new system for nondestructive evaluation of applied stress on the pipeline steels surface is proposed. This system is based on applying a magnetic field on the pipe surface, whose direction changes due to rotatory permanent magnets. The variation of magnetic field direction produces the Barkhausen signal, which is measured by a pick-up coil. The angular dependence of the magnetic Barkhausen noise signal energy is influenced by the pipe surface curvature due to the changing head-probe liftoff. Also, the said angular dependence changes with the applied tensile stress due to the magneto-elastic effect. The result of Barkhausen noise measurements in the pipeline surface submitted to applied tensile stress reveals that, since the effect of curvature on the angular dependence remains constant, the effect of applied stress could be determined by analyzing the angular dependence variation of the Barkhausen signal with the applied stress.

We report the crossover of Barkhausen noise statistics upon a change in the measurement geometry. The behaviour is akin to the angle dependent critical to sub-critical crossover of avalanche statistics as present in avalanche models with random anisotropy directions. The samples studied were 15-25 nm thin films of iron, grown on (001) GaAs by pulsed laser ablation. Use of planar Hall effect as a probe for the magnetic state facilitated this work, which would be impractical to do in a MOKE setup. We compare our data with simulations of a random anisotropy Ising model, and demonstrate striking similarity between experimental and simulated avalanche size distributions. Further, through micromagnetic simulations, we conclude that crystallite misorientations were the origin of domain wall pinning in our system leading to Barkhausen noise.

This paper reports the non-destructive evaluation of railway wheels via the Barkhausen noise technique across the wheel width. This study correlates non-destructive Barkhausen noise parameters with conventional destructive analyses expressed in terms of metallographic and SEM observations, microhardness profiles, residual stress, and average grain size measurements. The condition of the wheel surface was altered remarkably due to the real and long-term wheel operation. The results of investigations indicate non-homogenous distribution of Barkhausen noise emission as well as the corresponding surface state with respect to the wheel width. Severe plastic deformation and superimposed elevated temperatures alter the grain size considerably in the near-surface as well as the subsurface region. It was found that Barkhausen noise is strongly correlated with the average grain size within the Barkhausen noise sensitive depth, whereas the correlation with the residual stress distribution is quite poor.

This study investigates alterations in magnetic anisotropy and the marked asymmetry in Barkhausen noise (MBN) signals after the uniaxial plastic straining of steel S235 obtained from a shipyard and used as standard structural steel in shipbuilding. It was found that the initial easy axis of magnetisation in the direction of previous rolling, and also in the direction of loading, becomes the hard axis of magnetisation as soon as the plastic strain attains the critical threshold. This behaviour is due to the preferential matrix orientation and the corresponding realignment of the magneto-crystalline anisotropy. Apart from the angular dependence of MBN, the asymmetry in the consecutive MBN bursts at the lower plastic strains is also analysed and explained as a result of magnetic coupling between the grains plastically strained and those unaffected by the tensile test. It was found that, by increasing the degree of plastic strain, the marked asymmetry in MBN tends to vanish. Moreover, the asymmetry in MBN bursts occurs in the direction of uniaxial tension and disappears in the perpendicular direction. Besides the MBN technique, XRD and EBSD techniques were also employed in order to provide a deeper insight into the investigated aspects.

International audience; A directional local magnetic measurement technique as example of measuring the angular dependence of the magnetic Barkhausen noise in electrical and construction steels at typical quasi-static frequency by the magnetic needle probe (MNP) method is presented. The directional measurement configuration of the MNP method is typical of a half-turn search coil sensor coupled to high gain analogue amplification and high order filtration stages, owing to its very weak induced electromotive force. The method exploits the MBNenergy(H) hysteresis cycle (time integration of the square of the MBN voltage signal as a function of the tangent excitation field H) and brings forth stable indicators possibly related to the Magnetocrystalline Anisotropy Energy (MAE). Experimental tests performed on grain-oriented Fe-Si and low carbon steel specimens, and comparison with the conventional search coil measurement results were worth the validation of the MNP method. These results put to the front the good directional selectivity of the MNP method over the conventional MBN sensors adversely affected by the transverse fields at the material surface. Eventually, the printed magnetic needle probe (PMNP) sensor was relatedly described to provide non-invasive directional measurements for continuous structural health monitoring.

This study is focused on the asymmetrical Barkhausen noise emission of a hard milled surface during cyclic magnetisation. The Barkhausen noise is studied as a function of the magnetising voltage and the hard milled surface is compared with a surface after heat treatment. The asymmetry in the Barkhausen noise emission after hard milling occurs due to the typical "sandwich" structure and the different magnetic hardnesses of the different layers beneath the free surface. Furthermore, this asymmetry is also due to the preferential orientation of the matrix in the direction of the cutting speed and magnetostatic fields, which hinder or favour the premagnetising process. Web of Science 14 5 art. no. 1293

International audience; 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.

Portevin–Le Chatelier deformation bands obey predictions of a simple mean-field model of critical avalanche dynamics., The plastic deformation of metal alloys localizes in the Portevin–Le Chatelier effect in bands of different types, including propagating, or type “A” bands, usually characterized by their width and a typical propagation velocity. This plastic instability arises from collective dynamics of dislocations interacting with mobile solute atoms, but the resulting sensitivity to the strain rate lacks fundamental understanding. Here, we show, by using high-resolution imaging in tensile deformation experiments of an aluminum alloy, that the band velocities exhibit large fluctuations. Each band produces a velocity signal reminiscent of crackling noise bursts observed in numerous driven avalanching systems from propagating cracks in fracture to the Barkhausen effect in ferromagnets. The statistical features of these velocity bursts including their average shapes and size distributions obey predictions of a simple mean-field model of critical avalanche dynamics. Our results thus reveal a previously unknown paradigm of criticality in the localization of deformation.

We present numerical findings on the behavior of the athermal nonequilibrium random-field Ising model of spins at the thin striplike ${L}_{1}\ifmmode\times\else\texttimes\fi{}{L}_{2}\ifmmode\times\else\texttimes\fi{}{L}_{3}$ cubic lattices with ${L}_{1}l{L}_{2}l{L}_{3}$. Changing of system sizes highly influences the evolution and shape of avalanches. The smallest avalanches [classified as three-dimension- (3D) like] are unaffected by the system boundaries, the larger are sandwiched between the top and bottom system faces so are 2D-like, while the largest are extended over the system lateral cross section and propagate along the length ${L}_{3}$ like in 1D systems. Such a structure of avalanches causes double power-law distributions of their size, duration, and energy with larger effective critical exponent corresponding to 3D-like and smaller to 2D-like avalanches. The distributions scale with thickness ${L}_{1}$ and are collapsible following the proposed scaling predictions which, together with the distributions' shape, might be important for analysis of the Barkhausen noise experimental data for striplike samples. Finally, the impact of system size on external field that triggers the largest avalanche for a given disorder is presented and discussed.

Barkhausen noise phenomenon depends on several parameters such as applied/residual stress, chemical composition (carbon content, inclusions, etc.), microstructural parameters (grain size, grain boundary distribution), and crystallographic texture of materials. Therefore, modeling Barkhausen noise from the material's characteristics is always a challenge due to the complexity of the phenomenon. This chapter reviews existing models on Barkhausen effect and provides details of their formulation on relating physical properties of ferromagnetic materials.

Barkhausen noise is well-known as a versatile tool for the evaluation of (applied/residual) stress and magnetic properties (for the sake of example: stress anisotropy and magnetic easy axes) and the detection of defects of the structure in ferromagnetic materials. Currently, another important application of this phenomenon is its capacity of estimating the magnetocrystalline anisotropy energy in ferromagnetic materials. This chapter explains in detail the method for computing the magnetocrystalline anisotropy energy in a polycrystal from X-ray texture, and electron backscatter diffraction measurements; it also explains how Barkhausen noise can be used to estimate magnetocrystalline anisotropy energy in low-carbon steels. Furthermore, the role that the crystallographic texture plays in the observed correlation between magnetocrystalline anisotropy energy and Barkhausen noise is also discussed. This finding suggests that Barkhausen noise is potentially important method for characterization of magnetic material properties.

This paper shows evidence of the capability of electron backscatter diffraction (EBSD) to accurately estimate the magnetocrystalline anisotropy energy (MAE) of API 5L steels. The crystallographic texture of five circular steel samples was characterized by X-ray global texture and EBSD microtexture measurements. The average MAE of each one of these samples was estimated from the set of individual grain orientations obtained from orientation maps measured by EBSD. The angular dependence of EBSD-derived MAE was compared with predictions made from X-ray texture and Barkhausen noise (BHN) measurements. The average MAE determined from the EBSD data is in good agreement with the predictions made from X-ray and BHN measurements for all the studied samples. This agreement can be explained by the fact that the number of grains used to predict the average MAE from the EBSD results was statistically sufficient to reproduce the MAE predicted by the other two methods. The EBSD measurement strategy for the accurate MAE estimation was established in terms of parameters such as the number of individual grain orientations to be measured, the sample's texture acuity and grain size, the use of equivalent orientations given by the statistical orthorhombic symmetry of the studied samples, and different measurement planes.

Barkhausen noise, driven by thermal fluctuations in stationary magnetic field, and Barkhausen jumps, driven by sweeping magnetic field, are demonstrated to be effects of different orders of magnitude. The critical magnetic field for domain walls depinning, followed by avalanched and irreversible magnetization jumps, is determined. Magnetoresistive response of NiFe/M/NiFe (M = Au, Ta, Ag) trilayers to stationary and sweeping magnetic field is studied by means of anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) measurements. Thermal fluctuations result in local and reversible changes of magnetization of the layers in thin film magnetic junctions, while the sweeping magnetic field results in reversible and irreversible avalanched domain motion, dependently on the ratio between the values of sweeping magnetic field and domain wall depinning field. The correlation between AMR and PHE responses to Barkhausen jumps is studied. The value of this correlation is found to be dependent on the α angle between the directions of magnetic field and current path.

Dynamic response of magnetic hysteresis, magnetic Barkhausen noise and magneto-acoustic emission in a soft ribbon and electrical steels was studied comprehensively. The measurements were performed under controllable magnetization conditions: sinusoidal/triangular waveforms of the magnetic induction and a triangular waveform of the magnetic field. Magnetizing frequency was varied in a wide range: f mag = 0.5 – 500 and 0.5–100 Hz for the ribbon and the electrical steels, respectively. Magnetization amplitude was fixed on a near-saturation level H max ≃ 100 A/m. Barkhausen noise signal was detected by a sample-wrapping/surface-mounted coil and differently filtered. It was found that intensity of the Barkhausen noise rises approximately as a square root function of the magnetizing frequency. Whereas, level of the magneto-acoustic emission follows the hysteresis loss trend with an additional linear term (classical loss component).

We have combined a flip-chip high-Tc dc SQUID magnetometer with a ferromagnetic flux antenna made from 250 insulated 25-μm-thick stripes of amorphous soft magnetic Vitrovac 6025 foil inserted through the pick-up loop of the superconducting flux transformer. The ferromagnetic flux antenna provides improved magnetic coupling of the high-Tc SQUID to magnetic fields of ~0.4 nT/Φ0 to ~0.18 nT/Φ0. The orientation of the stripes was chosen to be normal to the foil tape rolling direction in order to minimize contributions from Barkhausen noise. A magnetic field resolution of ~2 fT/√Hz at 1 kHz and 77 K was achieved. Details of the technology and noise spectra of the novel composite high-Tc SQUID sensor are presented and their prospective applications for biomagnetic research and nondestructive evaluation are discussed.

In the present work a model for the correlation between magnetocrystalline anisotropy energy and Barkhausen noise is proposed. The link between the magnetocrystalline anisotropy energy and the magnetic Barkhausen noise is due to the influence of the crystallographic texture on the domain nucleation process which produces the Barkhausen signal in the branch from saturation to remanence. The statistical distributions of magnetic free poles and local fields of nucleation and subsequent growth of reversed domains were obtained for a large number of grain boundaries and used to estimate the number and size of Barkhausen events at each angular position from 0 to 360° in ten degree-steps. The good agreement observed between the modeled magnetocrystalline energy and the prediction of this energy made from X-ray texture and Barkhausen noise measurements corroborates the validity of the proposed model.

The paper presents a new concept for evaluation of surface damage of rails subjected to long-term cyclic loading. A rail cyclically loaded during 20 years of traffic was examined by combination of several non-destructive techniques with high sensitivity to surface damage, namely positron annihilation spectroscopy, X-ray line profile analysis and magnetic Barkhausen noise. The parameters of magnetic Barkhausen noise were correlated with the parameters describing the rail surface integrity, i.e. thickness, hardness, stress state and microstructure of the damaged layer. Good correlation between these parameters was observed and it has been demonstrated that thickness of the damaged layer can be measured non-destructively by the magnetic Barkhausen noise technique. Cyclic loading of the rail introduced a high density of dislocations into the sub-surface region and also vacancies which agglomerated into small clusters. Phase analysis of the rail surface revealed that repeated severe plastic deformation induced multiple phase transitions.

Twin-disk tests are an effective method to characterize the material response to rolling sliding contact, to reproduce the damage phenomena of real components at a laboratory scale in controlled working conditions. Usually the monitoring is performed by means of “gross” parameters, such as weight loss, coefficient of friction and Barkhausen noise, and micrographs of the sample sections, at the end of the test. Visual inspection of the sample contact surface at the macro-scale yields further information about the process under analysis. In twin-disk tests, the samples are visually inspected at predetermined steps, typically by acquiring the image of their surface when the samples are stationary. The availability of a system able to capture the images of the samples while they roll during the tests is of interest to better monitor the damage evolution. In this paper, we present the results of the experiments carried out to extract quantitative information from the images captured on railway wheel samples during rolling contact tests: suitable image processing has been designed with the objective of finding meaningful, synthetic indices for the monitoring and the interpretation of the wear process, also in relation to prior knowledge about the process. The experimental work was focused on the definition of the indices, on the analysis of their behavior on different steels, and on their usefulness to predict uneven wear during the tests on the test bench.

This study has been done by separately measuring Magnetic Barkhausen noise (MBN) under different structure characteristics, namely the carbon content, hardness, roughness, and elastic modulus in commercial steels. The result of the experiments shows a strong dependence of MBN parameters (peak height, Root mean square (RMS), and average value) on structure characteristics. These effects, according to this study, can be explained by two kinds of source mechanisms of the MBN, domain wall nucleation and wall propagation. The discovery obtained in this paper can provide basic knowledge to understand the existing surface condition problem of Magnetic Barkhausen noise as a non-destructive evaluation technique and bring MBN into wider application.

This work analyzes the differences between the magnetic Barkhausen noise corresponding to the initial magnetization curve and Barkhausen noise corresponding to one branch of the hysteresis loop in API-5L steel. The outcomes show that the Barkhausen noise signal corresponding to the initial magnetization curve and that corresponding to the hysteresis are significantly different. This difference is due to the presence of different processes of the domain wall dynamics in both phenomena. To study the processes present in magnetization dynamics for an applied field of H > 0, research into the angular dependence of a Barkhausen signal using applied field bands has revealed that a Barkhausen signal corresponding to the initial magnetization curve is more suitable than a Barkhausen signal corresponding to the hysteresis loop.

A relationship between microstructural steel features and an outcome of the Barkhausen noise (BN) measurement was studied. Two different microstructures, martensite and pearlite-ferrite were used. Commonly, BN is linked directly to the sample hardness. A BN outcome from both martensite and pearlite-ferrite was, however, similar even though martensite has three times higher hardness. To reveal the connection between microstructural features and BN, a typical industrial BN measurement was mimicked by in-situ transmission electron microscopy (TEM). Martensite needed higher field strength to move domain walls (DWs) than pearlite-ferrite. In martensite, DWs gathered to areas with high dislocation density. Fe3C lamellae in pearlite were strong pinning sites. DWs perpendicular and parallel to martensite laths started to move with the same field strength value. In pearlite, DWs perpendicular to lamellae started to move before the parallel ones. The RMS envelope of ferrite-pearlite starts earlier than that of martensite due to soft ferrite. Magnetically harder pearlite probably caused “a tail” and the envelope ends almost at the same time with martensite. . Nevertheless, similar peak width values were found for both samples. Martensite and pearlite have a lot of strong pinning sites, dislocations and Fe3C, respectively. Fe3C density is not as high as dislocation density. Ferrite has strong pinning sites only at low incidence, but as known, huge BN information volume compared to martensite and pearlite. This resulted in the similar pulse count from martensite and ferrite-pearlite. publishedVersion

A new method is presented for the estimation of the angular dependence of the magnetocrystalline energy from Barkhausen noise in API 5L steels in the branch from saturation to remanence. The magnetocrystalline energy was predicted from X-ray texture measurements and compared with the estimations produced from Barkhausen noise measurements in circular samples of six steels with different microstructures, crystallographic textures, and measuring planes. The angular dependences of the magnetocrystalline energy obtained from Barkhausen noise were in good agreement with the predictions made from X-ray texture measurements for all the studied steel samples and measuring planes. The results of this study corroborate that Barkhausen noise measurements based on the proposed method have the ability of accurately determining the magnetocrystalline energy in low-carbon steels and confirm that the strong correlation between the magnetocrystalline energy and the angular dependence of the Barkhausen noise signal is mainly due the role that crystallographic texture plays in the magnetization process of ferromagnetic materials in the branch from saturation to remanence.

The non-destructive testing methods based on Barkhausen noise and eddy current are very versatile and flexible. The application of these techniques in materials and components testing, production processes and new fields of utilization has been an aim of the authors for almost one decade of research. This paper provides an overview of the history of micromagnetic testing, the fundamentals of micromagnetism in ferromagnetic materials and allows an insight into several ongoing research projects in the wide-ranging fields of materials characterization and production engineering.

Barkhausen noise emission in soft magnetic bilayer ribbons has been investigated. The monolithic amorphous Fe73.5Nb3Si13.5B9Cu1/Fe74.5Nb3Si13.5B9 bilayer system was produced by double-nozzle melt-spinning. It was subsequently used to measure the Barkhausen noise emission in the amorphous state as well as in the annealed state as a function of magnetizing voltage. The asymmetry of the Barkhausen noise emission during cyclic magnetization was also investigated. It was found that the amorphous ribbon produces the conventional single burst, whereas the annealed ribbon emits bursts in which Barkhausen noise originating from the different layers can be easily distinguished. Moreover, a gentle asymmetry in the consecutive Barkhausen noise envelopes produced by ascending and descending magnetic fields was detected. The hysteresis loop for the annealed ribbon exhibits a two-step magnetization process in which the contribution of the different layers can be clearly distinguished.

This paper investigates the potential of Barkhausen noise emission for characterisation of soft magnetic composites based on ferromagnetic powders and resin coating. The powder samples are investigated as a function of variable resin fraction, as well as particle size, by the use of Barkhausen noise and EBSD techniques. Magnetic domain wall’s thickness and energy are calculated and the first constant of magneto-crystalline anisotropy is determined from magnetisation curves measured via a vibrating magnetometer. Moreover, the domain walls alignment is analysed and correlated with the Barkhausen noise signals and the extracted parameters. It was found that a reduced resin fraction, as well as increasing particle size of the ferromagnetic particles, contributes to the stronger Barkhausen noise emission. In this particular case, the Barkhausen noise emission strongly correlates with the coercive field whereas the correlation with hysteresis loss is weaker.

A magnetic method for the in-situ inspection of the combined effects of both, clamping force (CF) and the distribution of the surface residual stress (RS) on a face milled workpiece are presented. FE simulations have been conducted and evaluated, illustrating the impact of clamping on the workpiece surface deflection and thus, the machining accuracy. Furthermore, magnetic Barkhausen noise (MBN) signals were acquired on a hot-work tool steel workpiece after three different milling procedures: Face milling, one pass of micro-milling and 38 passes of micro-milling. Finally, the MBN signal on the unclamped workpiece was obtained. The MBN signal energy MBNenergy presented the highest values with the probe oriented in the pick (clamping) direction for all stages of milling process where the CF was applied. After unclamping the workpiece, the higher value of the MBNenergy was obtained with the probe oriented in feed direction of the milling processes revealing the true effect of the RS. These results were in agreement with the literature and confirmed by numerical simulations and X-ray diffraction based residual stress measurements.

Two kinds of thermally aged Fe-Cu alloys with different Cu proportions 0.05% and 0.45% were prepared and their magnetic properties were investigated to apply magnetic nondestructive testing techniques for the assessment of irradiation embrittlement of materials. Initially, the alloy is 10% cold rolled and then isothermally aged at 500 °C and 400 °C with different aging time up to 1000 h in order to create Cu-precipitates in the Fe metal matrix. The hysteresis loop (HL), Barkhausen noise (BN) and Magnetic Adaptive Testing (MAT) parameter were measured for magnetic properties studies and mechanical properties were investigated by Vickers hardness. The HL, BN were decreased and the MAT parameter was increased by thermal aging. The changes of these parameters were explained by copper rich precipitations (CRPs) formation, interaction with domain walls and dislocation movement pinned by CRPs. It was confirmed by TEM and EDX analysis.

Austenitizing and tempering temperatures are the effective characteristics in heat treating process of AISI D2 tool steel. Therefore, controlling them enables the heat treatment process to be designed more accurately which results in more balanced mechanical properties. The aim of this work is to develop a multiresponse predictive model that enables finding these characteristics based on nondestructive tests by a set of parameters of the magnetic Barkhausen noise technique and hysteresis loop method. To produce various microstructural changes, identical specimens from the AISI D2 steel sheet were austenitized in the range 1025–1130 °C, for 30 min, oil-quenched and finally tempered at various temperatures between 200 °C and 650 °C. A set of nondestructive data have been gathered based on general factorial design of experiments and used for training and testing the multiple response surface model. Finally, an optimization model has been proposed to achieve minimal error prediction. Results revealed that applying Barkhausen and hysteresis loop methods, simultaneously, coupling to the multiresponse model, has a potential to be used as a reliable and accurate nondestructive tool for predicting austenitizing and tempering temperatures (which, in turn, led to characterizing the microstructural changes) of the parts with unknown heat treating conditions.

Magnetic Barkhausen Noise (MBN) and Magneto Acoustic Emission (MAE) were studied in A508 Class II forged steel used for pressure vessels in nuclear power stations. The magnetic experimental determinations were completed with a macro graphic study of sulfides and the texture analysis of the material. The analysis of these results allows us to determine connections between the magnetic anisotropy, texture and microstructure of the material. Results clearly suggest that the plastic flow direction is different from the forging direction indicated by the material supplier

Magneto-acoustic emission (MAE) in a grain-oriented electrical steel is measured in a wide range of the magnetizing frequencies f mag = 0.5 − 100 Hz at the controllable sinusoidal/triangular waveforms of the magnetic induction B(t). Magnetic field is measured directly by a Hall sensor positioned on the steel surface. Intensity of the MAE signal (rms value) follows a loss separation formula a f mag + bf mag + c and reveals a linear relationship with the hysteresis loss. Number of the MAE individual pulses drops with the magnetizing frequency hyperbolically. Shape of the induction waveform at the fixed magnetizing amplitude and frequency has no visible impact on the above-mentioned behaviour. However, rms profiles of the MAE signal are driven by the field rate of change dH / dt . Integration of the MAE profiles allows to evaluate the hysteresis coercive field.

Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were applied to follow changes. It is shown, that observed bursts can be explained only with appearance of acoustic Barkhausen Effect (ABE). Interesting source localization is shown during heat treatment and consecutive stress test, which can be explained acoustic emission due to material transition from martenzit phase to bainite phase. Observed ABE opens the way to apply it in industry using magnetic stresses to provoke acoustic response for characterization of the state of the magnetic materials.

This paper deals with extraction of pure Barkhausen noise from the raw signals received in high-frequency regimes. The raw Barkhausen noise signals measured in high-frequency regimes contain components which cannot be attributed to the interaction of Bloch Walls with pinning sites and stress states such as the thermal noise of the sensor and the mechanical vibrations of the sensor-exciting core. Due to the variable ratios of thermal noise to Barkhausen noise as well as distortion of the signal due to vibrations, the raw signal as received and the pure Barkhausen noise signal can differ remarkably, thus making signal interpretation a debatable issue. For this reason, the post-processing method of the measured signal is presented here. In addition, the properties of μScan 500 device are analysed in detail.

The statistics and form of avalanches in a driven system reveal the nature of the underlying energy landscape and dynamics. In conventional metallic ferromagnets, eddy-current back action can dominate the dynamics. Here, we study Barkhausen noise in Li(Ho,Y)F4, an insulating Ising ferromagnet that cannot sustain eddy currents. For large avalanches at temperatures approaching the Curie point, we find a symmetric response free of drag effects. In the low temperature limit, drag effects contribute to the dynamics, which we link to enhanced pinning from local random fields that are enabled by the microscopic dipole-coupled Hamiltonian (the Ising model in transverse field)., 14 pages, 3 figures

Previous studies of Barkhausen noise in PZT have been limited to the energy spectrum (slew rate response voltages versus time), showing agreement with avalanche models; in barium titanate other exponents have been measured acoustically, but only at ambient temperatures. In the present study we report the Omori exponent (-0.95$\pm$0.03) for aftershocks in PZT and extend the barium titanate studies to a wider range of temperature., Comment: 10 pages and 17 figures

This paper investigates magnetic field and stress-induced magnetic domain reorientation and its correlation with Magnetic Barkhausen Noise (MBN). The magnetic domain dynamics and MBN of grain-oriented transverse and longitudinal electrical steels are studied by using time-resolved magneto-optical imaging. Time and frequency-domain characteristics of MBN signal are investigated for evaluation of stress state and magnetocrystalline anisotropy. Transitions between magnetic domain states with differing tensile stress and magnetic anisotropy directly influence the MBN signal. Its shown that 180° domain wall (DW) reorganization and DW-type conversion generate peaks in the MBN measurement for longitudinal and transverse electrical steel, respectively. The magnetic domain imaging reveals complicated domain arrangement processes in transverse electrical steel. The results provide a physical insight into bulk micromagnetic phenomena.