Barkhausen Signal Research Articles

Streamlining Barkhausen effect measurements: A simplified apparatus approach

The application of the Barkhausen Effect technique is hindered by the complexity and need for standardization in Barkhausen measurement devices. These devices typically comprise several modules for excitation, measurement, conditioning, and signal acquisition/processing, making them more complex than simpler methods such as Eddy Current or Magnetic Flux Leakage. Variations in device parameters among researchers can affect result consistency and interpretation. To address this issue, we propose a streamlined Barkhausen device consisting of a low-complexity measurement-excitation unit directly connected to the power grid. In the proposed device, nearly all signal conditioning and processing are transitioned from hardware, as used in the classic Barkhausen setup, to digital processing. This transition significantly enhances the standardization of the resultant Barkhausen signal. Comparative analysis between this simplified device and a traditional setup revealed no significant differences in signal parameters. The proposed device could function as a portable solution for preliminary tests to determine the feasibility of using the Barkhausen measurement technique. Adopting this simplified device could enhance the utility of the Barkhausen technique across various applications.

A three-dimensional numerical model for computing the actual voltage induced in a Barkhausen surface coil

This investigation presents a novel three-dimensional simulation model designed for the analysis of Magnetic Barkhausen Noise (MBN). The model’s formulation is directly deduced from Maxwell’s equations, establishing a Boundary Value Problem (BVP) with boundary conditions tailored to a specific configuration involving a lengthy steel rod encased within a solenoid, subjected to sinusoidal current excitation, all contained within an air enclosure. This chosen configuration holds physical equivalence to the majority of setups commonly utilized in Barkhausen experiments. Utilizing the proposed three-dimensional model, it became feasible, for the first time, to computationally assess the voltage induced in the coil by the flux emanating from all spatial directions. The findings indicate that the MBN signal is primarily generated by the flux rate aligned with the direction of the applied field. Nevertheless, simulations confirm additional contributions to the signal originating from magnetic flux in directions significantly deviating from the applied field direction. It is demonstrated that these contributions from lateral flux significantly influence the angular dependence of the Barkhausen signal energy, showcasing a notable alignment between the proposed model and experimental results. The results underscore the capability of the proposed model to facilitate the simulation of Barkhausen Noise.

Application of Machine Learning Techniques to Determine Surface Hardness Based on the Barkhausen Effect

Abstract Ensuring product and part quality impacts manufacturing productivity, efficiency and profitability. The goal of every manufacturing company is to quickly identify reduced quality in order to take appropriate measures to improve quality. The use of non-destructive testing methods such as Barkhausen noise in combination with artificial intelligence (AI), which immediately classifies the data, offers a way to implement the desired quality monitoring in a production line. In the present study, the measured data of the Barkhausen signal of surface hardened components with different degrees of tempering were analyzed. For this purpose, suitable AI models were developed and trained with the processed measurement data to generate prediction values for the surface hardness. Data preparation and further processing was carried out using the Spyder development environment with the Python programming language. The following models were applied, tested and optimized during the study: Support vector machine, random forest regression and an artificial neural network. The models were able to predict hardness levels with high accuracy after effective training. Overall, the neural network showed the best results. The applied procedures and methods are fast, non-destructive and provide results with acceptable measurement error, which allows their use in the production environment. Further improvements will be sought in the future, e. g. by applying a larger amount of training data, by changing the features used in the training and by increasing the measurement accuracy when capturing the Barkhausen signal.

What does a Barkhausen surface coil actually measure ?

The surface coil, which measures the magnetic flux rate from the sample surface, is the most used sensor for Magnetic Barkhausen signal measurement. However, there is little knowledge about how the magnetic flux corresponding to Barkhausen events is leaked from the sample surface and which components of the magnetic flux density contributes to the induced signal. The present work shows an effort to answer these questions by measuring the normal and tangential components of the signals induced in the surface coil and analyzing these measurements using a micro-mesoscopic model of Barkhausen effect. The results show that the presence of even a small tilt angles of the surface coil induces not only components of the applied field in the coil, as thought so far, but also induces tangential components of the Barkhausen signal. The presence of both components of the Barkhausen effect in the induced signal due to the tilt of the surface coil could be a result of the sample surface irregularities or due to the non-uniformity of the coil winding. Finally, the outcomes also reveal that magnetic flux contributing to the induced signal comes from a ring of the material surface surrounding the surface coil. These findings have important implications for Barkhausen setup and applications.

Measurement Potential of the Barkhausen Effect for Obtaining Additional Information on the Component Condition in Manufacturing

AbstractThe measurement of Barkhausen noise is one of the non-destructive testing methods which allows the use within the production line and within the cycle time at a high production volume. The aim of the present study was to answer the question, whether it is possible to extract the informations that the Barkhausen noise includes, concerning work-piece conditions, from the signal characteristic and more important assigning these findings. Therefore, soft machined and heat treated shaft components made of the ferromagnetic material Cf53 (1.1213) were analyzed to find characteristics in the Signal that allow to separate clearly an increase in temperature of the tested area from a change in the microstructure. For this purpose the shafts were analyzed at higher temperatures (up to 80 °C) and after an additional annealing process (to change the microstructure specifically). Both investigated situations (higher temperature and modified microstructure) showed different characteristic in the Barkhausen signal, thus an assigning is possible. Metallographic investigation and hardness measurements has been carried out to support the results.

Research on pipeline internal stress detection technology based on the Barkhausen effect

Focusing on the requirements of pipeline in-line testing for stress concentration, mechanical scratches and corrosion discrimination, a numerical calculation and experimental verification study of the internal testing excitation of oil and gas pipelines based on the Barkhausen effect (magnetic Barkhausen noise (MBN)) is carried out. This paper uses finite element calculation to determine the optimal position of the sensor, quantitatively analyses the influence of parameters, such as the excitation structure size and excitation intensity, on the magnetisation field of the pipeline and obtains the optimal exciting parameters for acquiring continuous Barkhausen signals, which can provide references for designing the pipeline in-line inspection gauge for stress concentration. The feasibility of the continuous Barkhausen noise (CBN) method for long-distance pipeline stress detection is verified by simulating the operating conditions of the internal detector in the pipeline using dynamic rotating excitation.

Enhancing the precision of magnetocrystalline anisotropy energy estimation from Barkhausen Noise using a deep neural network

Recent works in the literature have demonstrated that the angular dependence of magnetocrystalline anisotropy energy could be estimated from magnetic Barkhausen noise in carbon steels using the energy of a Barkhausen signal band associated with the magnetic domain nucleation. However, although the estimations of this magnitude using the Barkhausen noise signal have practical advantages with respect to X-ray method, it is not as precise as the latter. This work proposes a method that uses a deep neural network for significantly enhancing the estimation precision of the shape of the angular dependence of the magneto-crystalline anisotropy energy using Barkhausen signal. Additionally, the proposed algorithm allows to estimate for the first time the amplitude of this angular dependence using the Barkhausen signal. The results are also compared with the determination of magnetocrystalline anisotropy energy using a feature selection method. The most significant features of the Barkhausen signal for computing the magnetocrystalline anisotropy energy are analyzed.

Variation of Barkhausen Noise, Magnetic and Crystal Structure of Ferromagnetic Medium-Carbon Steel after Different Loading Processes

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.

A model for the influence of plastic deformation on Magnetic Barkhausen Noise in carbon steel

In this work, a model for the influence of tensile plastic deformation on Barkhausen Noise is proposed. This model is based on a previous model that allows to explain the influence of magnetizing parameters, applied field frequency and electric conductivity on Barkhausen Noise. In order to analyze the effects of plastic deformation on Barkhausen Noise, the model was modified to include the presence of dislocations tangles, the change of the mean coercivity and the change of local coercive field standard deviation as a function of the tensile plastic deformation. The simulations of the model are compared with Barkhausen signal, obtained from three different steel subjected to six levels of plastic deformation. The experimental results show that the amplitude of Barkhausen signal decreases, the main peak field increases and the signal envelope width increases with the increase of tensile plastic deformation. The simulated Barkhausen envelope shows the same behavior as the experimental envelope considering that the number of dislocation tangles increase, the mean value of the local coercive field increases and the standard deviation of the local coercive field increases with the increase of plastic deformation.

Barkhausen noise signal of different steels upon face-turning process

This paper deals with understanding the effects of excitation field parameters on the nature of Barkhausen noise profile in order to improve the validity of Barkhausen noise results for the machining process. The experiment has been performed on total of four samples, two of high carbon steel and two of high carbon chromium steel. First, all samples are subjected to process annealing and later one sample of each steel was subjected to face-turning process. Barkhausen noise measurement was performed in two steps: first, magnetizing frequency varied and magnetic field intensity kept constant, and second, magnetic field intensity varied and magnetizing frequency kept constant. Magnetic Barkhausen noise profile is obtained by fitting Gaussian function to the root-mean-square distribution of the Barkhausen signal. The complicated behaviour of the profiles with frequency suggests optimum frequency determined statistically, which reflects the stochastic behaviour and can be applied to describe and control the face-turning process. The peak value of the profiles with amplitude of the sinusoidal magnetic field intensity has found to resemble exponential decay correlation.

A novel system for non-destructive evaluation of surface stress in pipelines using rotational continuous magnetic Barkhausen noise

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.

Effect of Barkhausen Detection Distance in Cold and Temper Rolled Low Carbon Steels: A Novel Approach

In this paper, a novel arrangement for magnetic Barkhausen noise detection is introduced. Measurements have been performed using two low carbon steel plates of 1 mm thickness. The measurements were conducted along the rolling and the transverse directions. The new arrangement includes a displacement of the detection coil in predetermined steps in while the magnetizing yoke is kept stationary introducing a cyclic magnetization in the rolling direction and transverse to it. In general, the intensity of the Barkhausen signals decreased as a function of coil displacement in both plates. In the temper rolled plate, Barkhausen noise profile shape changed from a single peak to a double peak one when coil has been displaced by 5 mm away in both magnetizing directions. Peaks are more apparent while magnetizing in the transverse direction. The appearance of two peaks profile in the temper rolled plate may be attributed to two stages of magnetization taking place at different times as a function of the applied field. Magnetization in the transverse direction results in a partition of the internal magnetizations into two main components perpendicular to each other. The internal components of magnetization involve the magnetic easy axes in the rolling direction and the forced magnetization in the transverse direction due to the applied field. Another assumption to interpret the findings may be due to the internal demagnetization field in the soft material below surface. The findings support this assumption in such a way that the demagnetizing field is strong enough in the transverse direction than in the rolling direction. This assumption is supported by the experiment on cold rolled plate. In the cold rolled plate, the resultant MBN profiles are composed of one peak throughout the test due to high dislocation density and hence a very weak demagnetizing field.

Non-destructive Case Depth Determination by Means of Low-Frequency Barkhausen Noise Measurements

The availability of a fast and reliable method for non-destructive case depth determination which can be used to directly monitor the quality of various heat treatment processes is of great interest. Conventionally hardened steel components are analyzed by means of depth-resolved microhardness measurements providing the case hardening depth (CHD) of the material. However, as a consequence of mechanical destruction, the investigated part cannot be used in its original state anymore and needs to be replaced by a twin part whose properties might be different. In this work, a new approach of non-destructive CHD determination based on Barkhausen noise analysis with an excitation frequency of 0.5 Hz is described. The use of a low frequency allows to enhance the penetration depth of the external magnetic field and to reduce the eddy current damping of the filtered Barkhausen (BN) signal at the same time. In this way, simultaneous information about the hard case and the soft base material core is experimentally accessible. Various measurands derived from the detected BN signals are sensitive to the different magnetic properties of the case and the core. The so-obtained correlations with the measured CHD can be used for non-destructive CHD determination by means of appropriate calibration data. The investigated sample set consists of cylindrical parts of 18CrNiMo7-6 which were case-hardened and ground in order to provide graded CHD values up to 3.6 mm. The sensitivity of the tested low-frequency method will be quantitatively demonstrated over the complete range of interest and its potential for industrial applications will be discussed.

Model for the correlation between magnetocrystalline energy and Barkhausen noise in ferromagnetic materials

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.

Barkhausen noise signal analysis of heat treated samples at various magnetising frequencies

Signal processing of magnetic Barkhausen noise was performed to reveal the useful information content of the signal which would otherwise difficult due to stochastic nature of the signal. Magnetic Barkhausen noise signal was measured from different heat treated steel samples which were further processed to investigate the effect of heat treatment on Barkhausen noise signal. The dependence of Barkhausen signal upon magnetising frequency was also discussed in terms of RMS value of Barkhausen noise envelope. Variation in the RMS value of the Barkahusen noise profile with magnetising frequency and mechanical properties was explained using micromagnetic theory. The present study shows that magnetic Barkhausen noise signal depends upon mechanical properties as well as on magnetising frequency which needs to be optimised in order to use magnetic Barkhausen noise as a characterisation tool.

Residual stress evaluation by Barkhausen signals with a magnetic field sensor for high efficiency electrical motors

The iron loss of industrial motors increases by residual stress during manufacturing processes. It is very important to make clear the distribution of the residual stress in the motor cores to reduce the iron loss in the motors. Barkhausen signals which occur on electrical steel sheets can be used for the evaluation of the residual stress because they are very sensitive to the material properties. Generally, a B-sensor is used to measure Barkhausen signals, however, we developed a new H-sensor to measure them and applied it into the stress evaluation. It is supposed that the Barkhausen signals by using a H-sensor can be much effective to the residual stress on the electrical steel sheets by referring our results regarding to the stress evaluations. We evaluated the tensile stress of the electrical steel sheets by measuring Barkhausen signals by using our developed H-sensor for high efficiency electrical motors.

Comparison of angular dependence of magnetic Barkhausen noise of hysteresis and initial magnetization curve in API5L steel

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.

Frequency fluctuation signal processing and its application to the Barkhausen signals

Frequency fluctuation signal processing and its application to the Barkhausen signals

Study of subsurface initiation mechanism for white etching crack formation

The present paper describes a novel way to detect early stages in the gradual transformation of SAE 52100 bearing steel material to white etching cracks (WEC). The underlying transformation is recorded and investigated by a complementary use of Barkhausen noise measurements, ultrasonic measurements and scanning electron microscopy. While ultrasonic measurements can only be used to detect cracks in a failed component, the recently improved Barkhausen noise measurement technique can be used to detect possible early stages of microstructural transformation. A cross section from a region without ultrasonic signal but with a Barkhausen signal has been investigated by the use of scanning electron microscopes in order to reveal possible pre-stages of WEC formation. These findings support that WEC are locally initiated in subsurface regions. Within those modified regions, carbides start to dissolve in consequence of deformation accumulation, which has been identified as an early state of WEA microstructure formation.This paper is part of a Themed Issue on Recent developments in bearing steels.

The Attempt of New Approach to Evaluate Surface Integrity

Machined surface of hard steel parts like gears, bearings, camshafts etc. is full of local imperfections which are commonly described in terms of surface integrity. This surface integrity is usually quantified with the level of residual stresses or amplitude of Barkhausen noise signal for instance. The contribution introduces parameter called Sum of Effective Residual Stresses (SERS) to describe the level of surface damage after grinding. Experimental data obtained by X-Ray Diffraction (XRD) and Barkhausen Noise Analysis (BNA) methods of ground gears are shown. The way to use SERS approach for experimental determination of penetration depth of Barkhausen signal in steels is proposed, too.