Barkhausen Noise Measurements Research Articles

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.

Multi-parameter Evaluation of Magnetic Barkhausen Noise in Carbon Steel

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

A System for Controllable Magnetic Measurements of Hysteresis and Barkhausen Noise

A specially developed setup for precise measurement of the magnetic hysteresis and Barkhausen noise is presented in this work. A novelty of the setup consists in a unique combination of two main features: an accurate local determination of the magnetic field and an improved feedback control of the magnetization process. Firstly, the magnetic field is measured by two Hall sensors at different distances above the sample. Linear extrapolation of this measured profile of the tangential fields to the sample surface gives the true local values of the magnetic field. Secondly, a digital feedback loop for precise control of the ac magnetization process is proposed. The system combines two known methods of magnetizing signal adjustment: linear corrections of the magnetizing voltage amplitude and phase. The presented system is able to adjust the waveform of the magnetic induction or field to the prescribed sinusoidal or triangular shape. This provides stable and physically accurate results, which are independent of a specific experimental configuration.

Determination of burn thresholds of precision gears in form grinding based on complex thermal modelling and Barkhausen noise measurements

Thermal damage control in high efficiency form grinding of precision gears is critical for obtaining the required gear surface integrity and ensuring the contact strength in service life. Complex thermal models have been developed to determine the variation of burn thresholds of power under different grinding parameters in form grinding mode of gears. The thermal models analyse in detail the variation of local contact geometry between the grinding wheel and gear surface, and the variation of heat partitioning to different thermal parts including the workpiece, wheel, grinding fluid and grinding chips. The burn thresholds of power in the form grinding of carbonised steel gears have been determined by relating the grinding temperature with the Barkhausen Noise and micro-hardness measurements for the ground surfaces. The models and the determined burn thresholds can be used for presetting the parameters and conditions of grinding process and monitoring the grinding process to avoid the occurrence of thermal damages to the gear surfaces.

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

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

Tool Geometry Influence on Surface Integrity of Machined Austenite Stainless Steel

The goal of this contribution was to describe the microstructure and properties changes of difficult to cut materials after turning. Surface residual stresses, roughness, microstructure of AISI 304 type stainless steel were studied as a function of side rake angle o. Residual stresses and phase composition of surface and sub-surface layers were determined using X-ray diffraction techniques. The presence of strain-induced martensite was investigated using Barkhausen noise, optical microscope, and microhardness measurement.

Investigation of Two-Stage Magnetic Barkhausen Noise Measurement Method at Power Line Frequency

Investigation of Two-Stage Magnetic Barkhausen Noise Measurement Method at Power Line Frequency

Evaluation of the Residual Stress State of 42crmo4 Steel Sheets in a Production Line

The residual stress state of a mechanical component is an important factor in its production planning and in estimates of its lifecycle since it can be responsible for geometric distortions and degradation of fatigue properties. Therefore, the development of reliable methods for non-destructively quantifying these stresses remains in the interest of most manufacturing industries; Barkhausen magnetic noise measurements have been investigated in several applications and remains a viable option. However, its effective implementation has occurred mostly in components with simple geometries and insignificant microstructural gradients; even in these cases, successful industrial adoption of the method depends on previous calibration with samples that are often difficult and costly to prepare and validate. This work aims at investigating the capability of the method of characterizing the residual stress state in a simple but generally useful application: samples of hot-rolled steel sheets collected at two different stages of processing in an industrial mechanical conformation and heat treatment plant. In this analysis Barkhausen noise measurements were compared to X-ray diffraction results, and statistical analysis tools were used to correlate the results.

An accurate method for determining residual stresses with magnetic non-destructive techniques in welded ferromagnetic steels

The scope of the present research work was to investigate the proper selection criteria for developing a suitable methodology for the accurate determination of residual stresses existing in welded parts. Magnetic non-destructive testing took place by the use of two magnetic non-destructive techniques: by the measurement of the magnetic Barkhausen noise and by the evaluation of the magnetic hysteresis loop parameters. The spatial distribution of residual stresses in welded metal parts by both non-destructive magnetic methods and two diffraction methods was determined. The conduction of magnetic measurements required an initial calibration of ferromagnetic steels. Based on the examined volume of the sample, all methods used were divided into two large categories: the first one was related to the determination of surface residual stress, whereas the second one was related to bulk residual stress determination. The first category included the magnetic Barkhausen noise and the X-ray diffraction measurements, while the second one included the magnetic permeability and the neutron diffraction data. The residual stresses determined by the magnetic techniques were in a good agreement with the diffraction ones.

New parameters in adaptive testing of ferromagnetic materials utilizing magnetic Barkhausen noise

A new method of magnetic Barkhausen noise (MBN) measurement and optimization of the measured data processing with respect to non-destructive evaluation of ferromagnetic materials was tested. Using this method we tried to found, if it is possible to enhance sensitivity and stability of measurement results by replacing the traditional MBN parameter (root mean square) with some new parameter. In the tested method, a complex set of the MBN from minor hysteresis loops is measured. Afterward, the MBN data are collected into suitably designed matrices and optimal parameters of MBN with respect to maximum sensitivity to the evaluated variable are searched. The method was verified on plastically deformed steel samples. It was shown that the proposed measuring method and measured data processing bring an improvement of the sensitivity to the evaluated variable when comparing with measuring traditional MBN parameter. Moreover, we found a parameter of MBN, which is highly resistant to the changes of applied field amplitude and at the same time it is noticeably more sensitive to the evaluated variable.

Examining the Correlation Between Microstructure and Barkhausen Noise Activity for Ferromagnetic Materials

Barkhausen noise emissions occur in ferromagnetic materials on application of an externally varying magnetic field. These emissions primarily occur due to the presence of pinning sites or discontinuities within a material which act as inhibitors to domain wall motion. Overall, Barkhausen noise emissions can capture variations in microstructure, chemical composition, lattice strain, and grain size, and can detect the presence of residual stresses in materials. In this paper, the Barkhausen noise response for a Jominy end-quench test steel sample is examined. Microstructural variations in the form of constituent phases, such as martensite, bainite, pearlite, or ferrite, can be detected via changes in Barkhausen noise signatures. Through Barkhausen noise measurements, it is observed that characteristic peaks corresponding to different phases appear in the spectrum. The characteristic peaks become distinct when the contribution to Barkhausen noise from individual phases becomes significant. This analysis method may be further used to monitor microstructural evolution, and thus understand the contributions of constituent phases to material properties. The technique may be used as a potential tool for the nondestructive evaluation of ferromagnetic materials employed in industrial applications.

An experimental procedure for surface damage assessment in railway wheel and rail steels

The assessment of damage in rail–wheel cyclic contact requires considering the combined action of different damage mechanisms, such as wear, ratcheting, surface or subsurface crack nucleation and propagation. Models, usually requiring experimental calibration, are available for assessing these phenomena. The best way to calibrate them is based on cyclic contact tests, as these represent the real working conditions more closely. However, some experimental information, such as microstructural changes or crack paths, can be obtained only by destructive methods at the end of the tests, and their evolution cannot be monitored; other parameters, such as the wear rate, can only be determined during time consuming breaks to the tests. In this work, non destructive measurements of vibrations, torque and Barkhausen noise were introduced as indicators of damage evolution in cyclic contact tests on a high performance steel for railway wheels, coupled with a rail steel. In particular, their correlation with surface state, wear rate, subsurface microstructure and presence of cracks was shown.

Optimizing Detection Parameters of Magnetic Barkhausen Noise Using Heat Affected Zone in Welded Ship Steel Plate

Magnetic Barkhausen noise measurements on a welded marine steel plate were performed in a line that passes through the weld bead and extends to the base metal from both sides of the weld. The heat affected zone was characterized by a pattern in the peak height as a function of distance from the weld bead. Barkhausen noise profile analysis by extracting relevant parameters like peak position, profile area and profile half width was also performed. The result showed a clear variation in MBN profile parameters in a way similar to that of the profile peak height. It could be concluded that MBN profile parameters superimposed as a function of measurement distance from the weld bead may provide an accurate determination of the affected material near the weld bead. The variation in MBN profile parameters was enhanced by microstructural and mechanical changes along the measurement line. This experiment demonstrates that the Barkhausen noise profile parameters could be used to track various manufacturing and maintenance processes of steel instead of using a single parameter like the root mean square (rms) to eliminate the variability of results and narrow the tolerance of acceptance criterion.

Variations of the Magnetic Permeability and Barkhausen Noise in a Welded Low Carbon Steel

The present paper investigates the utilization of both the magnetic Barkhausen noise and permeability measurements for the nondestructive distinguish of the three welding zones in a welded low carbon steel.

Anisotropic Magnetic Properties of MilledBearing Steel Surface

For many reasons, the steel surfaces are machined to obtain required physical properties. Suitable methods are required for the management and control of the manufacturing processes, which are simultaneously su ciently robust and sensitive. The non-destructive testing methods, sensitive to the magnetic properties of the surface, are very suitable for this purpose. The Barkhausen noise (BN) measurement, which reveals the discontinuous movement of the magnetic domains in the thin surface layer during magnetisation reversal process is very robust, while magneto-optical Kerr e ect (MOKE) method, using polarized light for orientation measurements of magnetic domains at the surface, is very sensitive and provides detailed information about hysteresis curves (HC) of the materials. In this contribution our results obtained on the milled 100Cr6 bearing steel are presented. These properties were obtained by MOKE laboratory measurements and bring very interesting facts about the magnetisation reversal process, which depends on the orientation of the magnetic eld with respect to the cutting direction. Our results clarify the strong anisotropy of BN, which is observed during the industrial application of this method.

Effect of <inline-formula> <tex-math notation="TeX">\(\alpha \) </tex-math></inline-formula>-Particle Irradiation on the Magnetic Properties of Ni Nanowires

We report the effect of α-particle irradiation on the magnetic properties of nickel (Ni) nanowires (NWs) arrays with diameter of each NW ~100 nm prepared by electrodeposition using anodic alumina oxide (AAO) membranes. Different doses of α-particles irradiation, up to 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> α/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> were used to observe the effect. Structural characterization indicates the reduction in crystallinity of Ni NWs after irradiation. Coercivity (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) was found to increase with α-particle dose due to the formation of pinning centers. The magnetic easy axis changed direction from in-plane (with AAO template) to the out-of-plane due to the decrease in magnetocrystalline anisotropy by α-particle irradiation. Furthermore, the effect of α-particle irradiation on Ni NWs was studied by magnetic Barkhausen noise measurements.

White Etching Crack Root Cause Investigations

White etching crack (WEC) failure is distinct to classical fatigue and driven by the composition of lubricants under special loading conditions; for example, slippage and electricity. The white etching area (WEA) within WEC contains carbon supersaturated ferrite (bcc-iron) and carbides, with a size of a few nanometers. This article presents investigations supporting the hypothesis that WEC processes start within a failure-free period by successive accumulation of a structural distortion. This can be measured by acoustic emission. Failure statistics show a steep ascent in the Weibull diagram (ß values beyond 1) leading to the assumption that WEC processes start unsuspicious, as one would see as a failure-free period, but imply a hidden subsurface accumulation of material defects. It is suggested and supported by the evidence presented within this article that WEC is neither related to the presence of nonmetallic inclusions nor related to other impurities in the steel. Instead, the failure is a sequence and accumulation of plastic deformations in the microstructure. Within the SAE 52100 material as discussed in this article, this accumulation is located in the microstructure around cementite, seen in a turn of hard magnetization toward soft magnetization proven by Barkhausen noise measurements. This decay is caused by the plastic deformation of such domains. Distortions in the vicinity of a cementite first would lead to carbon supersaturation by diffusion processes and later to a plastic deformation of the carbides. In the end, the complete distorted region will release the accumulated energy by downsizing the microstructure toward WEC.

Numerical and Experimental Determination of the Residual Stress State in Multipass Welded API 5L X70 Plates*

Abstract Residual stress distributions in multipass welded API 5L X70 steel plates were determined by numerical and experimental methods. SYSWELD finite element software was used for numerical simulations. Microstructure variations were also considered for calculation of residual stresses. The continuous cooling transformation diagram was obtained via JMatPro software. The results showed that residual stress distribution is sensitive to number of weld passes, and microstructure changes. The simulation results were compared with those obtained by Magnetic Barkhausen Noise measurements on the welded plates. Simulation and experimental results gave qualitatively similar tendencies for the variation of the residual stress state.

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

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

Two-stage method of Barkhausen noise measurement

A simple method of measuring the Barkhausen noise in two stages was developed. The purpose of the proposed method was to remove the magnetizing frequency component from the induced electromotive force signal without using complex analog or digital filters, which also suppress the Barkhausen noise. In the first stage, an instance of the electromotive force signal was temporarily recorded, and in the second stage another instance of the electromotive force signal subtracted from the previously recorded instance of the electromotive force signal was measured. Using this method we will obtain only the stochastic component of the electromotive force signal – the Barkhausen noise. The method is illustrated on measuring the Barkhausen noise in an electrical steel sample. The experiments proved that with this method we are able to remove the dominant continuous component from the induced electromotive force signal and we can simplify the measurement. The general problems associated with the method are discussed.