Barkhausen Noise Method Research Articles

Dependence of Barkhausen Noise in Plastically Deformed Steel on Frequency and Nonlinearity of Magnetizing Field

The Barkhausen noise was measured in plastically deformed low-carbon steel at various frequencies of the magnetizing fleld. Strip samples magnetized by a yoke were used for investigation. The measured amplitude distributions and power spectra are compared with the results of the Alessandro, Beatrice, Bertotti, Montorsi model of the Barkhausen noise. The measurement results at the triangular magnetizing current and the triangular magnetic fleld in the sample were compared and the difierences will be discussed. The Barkhausen noise (BN) method of nondestructive testing provides good sensitivity to residual stress levels and changes in the microstructure of a magnetic material. In this work, the BN was measured in plastically deformed low-carbon steel. Plastic deformation changes the average number of individual pulses in large Barkhausen jump due to the change of the dislocation density and distribution of residual microstresses in the sample. The in∞uence of the plastic deformation on the BN is usually investigated using the deflned (triangular or sinusoidal) magnetizing current with some low frequency [1]. In this paper, we tried to investigate the in∞uence of the magnetizing frequency on the measurement results. In addition, when the triangular current from the power amplifler is used as magnetizing current in coils of the yoke, the nonhomogeneity of magnetic circuit causes that the magnetic fleld in the sample is not proportional to the current, and therefore the fleld rate is not constant [2]. Further, the magnetizing frequency and the deformation of samples heavily in∞uence the nonlinearity of the sample magnetization characteristic, so the samples are not measured with the same fleld amplitude. To impose the constant fleld rate with the deflned fleld amplitude, the fleld was measured by the tangential Hall probe on the sample surface and the digital feedback was used. The impact of this feedback on measurement results will be discussed.

Characterization of Dual-Phase Steels Using Magnetic Barkhausen Noise Technique

The aim of this work is to nondestructively characterize the dual phase steels using the Magnetic Barkhausen Noise (MBN) method. By quenching of AISI 8620 steel specimens having two different starting microstructures, from various intercritical annealing temperatures (ICAT) in the ferrite-austenite region, the microstructures consisting of different volume fractions of martensite with morphological variations have been obtained. The microstructures were first conventionally characterized by metallographical investigations and hardness tests. Then, the MBN measurements were performed using a μSCAN commercial system. Good correlations between the martensite volume fraction, hardness and MBN emission have been obtained. MBN signal height clearly decreased as the ICAT, therefore the volume fraction of martensite increased. The effect of the initial microstructure prior to intercritical annealing has also been differentiated by the MBN measurements. It has been concluded that MBN method can be used as a useful tool for nondestructive characterization of dual phase steels.

Monitoring the Microstructural Changes During Tempering of Quenched SAE 5140 steel by Magnetic Barkhausen Noise

The aim of this work is to characterize the microstructures of quenched and tempered steels non-destructively by a diverse set of parameters of the Magnetic Barkhausen Noise method (MBN fingerprint, frequency spectra, pulse height distribution, root-mean-square, and total number of pulses). Identical specimens from a SAE 5140 steel bar were prepared. All specimens were austenitized at 860°C for 30 minutes and water-quenched identically. The quenched specimens were then tempered at various temperatures between 200°C and 600°C. The microstructures were characterized by metallographic examinations and hardness measurements. Pulse height distributions, noise signal envelopes and frequency spectra were used to evaluate Barkhausen activity. The results show that as the tempering temperature increases, the Barkhausen activity increases due to the enhancement of domain wall displacement with softening of the martensite. An excellent correlation was found between Barkhausen parameters and hardness values.

Comprehensive analysis of Barkhausen noise properties in the cold rolled mild steel

Low carbon steel specimens cold rolled at ratios of 0%, 5%, 10%, 20% and 40% have been comprehensively investigated by magnetic Barkhausen noise method, and their microstructures were studied by transmission electron microscope. A broad peak formed between 15 and 60 kHz in the fast Fourier transformation spectrum increases with rolling ratio. Barkhausen noise energy and rms voltage rise rapidly with cold rolling below 20%, and saturate at higher rolling ratio. This phenomenon is attributed to the combined effects of cell texture and dislocation density.

Comparison of magnetic Barkhausen noise and ultrasonic velocity measurements for microstructure evaluation of SAE 1040 and SAE 4140 steels

The aim of this study is to compare the performance of magnetic Barkhausen noise and ultrasonic methods for the evaluation of the microstructure of commercial steels. Following the austenitization of the specimens made of SAE 1040 and SAE 4140, various heat treatments were carried out to obtain microstructures consisting of martensite, tempered martensite, fine pearlite–ferrite, and coarse pearlite–ferrite. The microstructures were initially characterized by SEM investigation and hardness measurements. The magnitude and position of Barkhausen noise peaks were determined via a commercial system. The propagation rates of longitudinal waves were determined with the ultrasonic pulse-echo technique. Barkhausen noise response and sound velocity goes to minimum for the as-quenched martensite, and both tend to increase in the following sequence: tempered martensite, fine pearlite–ferrite, and coarse pearlite–ferrite. However, the magnetic features are more sensitive to the microstructure variations than to the sound velocity.

Investigation of as-quenched and tempered commercial steels by Magnetic Barkhausen Noise method

This study aims to characterise as-quenched and tempered steels by the Magnetic Barkhausen Noise method, and to contribute to optimisation of heat treatment processes. Identical austenitisation and quenching procedures were applied to SAE 1040 and SAE 4140 specimens to eliminate the effect of grain size. Samples were tempered at 200°C and 600°C for 2 hours. Microstructures were characterised by metallographic examinations and hardness measurements. Amplitude, position and frequency spectrum of signals were evaluated using a commercial system. As the tempering temperature increases, in contrast to the reduction in hardness, magnetic response increases due to the enhancement of domain wall displacement.

Fusion of electromagnetic inspection methods for evaluation of stress-loaded steel samples

The magnetic leakage flux, multifrequency eddy current and Barkhausen noise methods were used to evaluate changes in materials properties induced by stress. Seven samples made of ferromagnetic low carbon steel with different stress level were prepared. The results showed tensile deformed samples at room temperature with a yield at around 350 MPa, residual strain between 0.7% and 14% and tensile stress from 100 MPa to 389 MPa.

Fatigue damage assessment in AISI 8620 steel using Barkhausen noise

The Barkhausen noise method has long been applied to measure time degradation of engineering materials. In this paper, fatigue damage evolution of an engineering structural AISI 8620 steel is studied by using Barkhausen noise measurements. The influence of applied alternating stresses and number of cycles on a Barkhausen noise parameter was evaluated. For stress range between fatigue and yield limit of the material, it was found that the Barkhausen noise increase with increasing applied stress. The Barkhausen noise increases rapidly at the begin of test, in the early stage of fatigue life. When the applied maximum stress is above yield limit of the material, plastic strain has to be accounted for, and no equivalence between fatigue damage and Barkhausen noise can be stated.

Effect of stress-induced martensite phase on barkhausen noise in Fe-30.2%Pd alloy

The possibility of detecting the phase transformation of stress-induced martensite in a ferromagnetic shape memory alloy Fe-30.2at%Pd thin foil was investigated by using the Barkhausen noise (BHN) method. Stress-induced martensite twining was observed by laser microscopy above a stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twining in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to the austenite phase at weak magnetic fields. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field levels. The BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.

Detectability of stress-induced martensite phase in ferromagnetic shape memory alloy Fe–30.2at.%Pd by Barkhausen noise method

The possibility to detect the phase transformation of stress-induced martensite in ferromagnetic shape memory alloy Fe–30.2at.%Pd thin foil was investigated by using Barkhausen noise (BHN) method. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twin in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.

107 磁性形状記憶合金スマート複合材料の設計と評価(OS 複合機能化材料・デバイスとその加工プロセス)

The possibility to detect the phase transformation of stress-induced martensite in ferromagnetic shape memory alloy Fe-30.2at%Pd thin foil was investigated by using Barkhausen noise (BHN) method. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twin in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.

Determination of welding residual stress distribution in API X65 pipeline using a modified magnetic Barkhausen noise method

A modified magnetic Barkhausen noise (MBN) method was applied to obtain the residual stress distribution in an API X65 pipeline weldment. Different weldment microstructures affected the magnetic response and yielded different MBN values. In order to reflect the microstructural variations in the heat-affected zone (HAZ), calibration samples were extracted from four different regions: weld metal, coarse-grained HAZ (CGHAZ), fine-grained HAZ (FGHAZ), and base metal. This approach yielded that compressive residual stresses existed in the CGHAZ contrary to the tensile results using the base-metal-based calibration method. Compared with the results from the mechanical saw-cutting method, it can be concluded that the data obtained with the HAZ-based calibration method were more reliable.

Relation between residual stress and Barkhausen noise in a duplex steel

The relation between residual stress and Barkhausen noise (BN) was evaluated in a duplex stainless steel. The residual stresses had been created to the test piece by local heating. Rms value, position of the maximum of the BN burst, its full width half maximum, power spectrum and pulse height distribution were characterised. All the parameters depended to some extent on the residual stresses and none of them was totally independent on the other parameters. The best parameter for the residual stress evaluation was the rms value of the BN amplitude. The rms value varied according to the total stress (macrostress+homogeneous microstress) in the ferrite phase. The stress component perpendicular to the direction of the magnetization had also some influence. Based on the results it is possible to evaluate the residual stresses of the ferrite phase of duplex stainless steels by the BN method.

Application of Barkhausen noise to biaxial residual stress measurements in welded steel tubes

The relationship between Barkhausen noise and biaxial stress was studied in mild steel specimens in as received and annealed conditions. In the as received condition the saturation stress of the Barkhausen noise was higher but the stress sensitivity was lower than in the annealed condition. In the as received condition the Barkhausen noise response was different in the rolling and transverse directions. In the annealed condition no difference was observed. The stress sensitivity was found to be independent of stress perpendicular to the magnetising direction in the annealed condition. In the as received condition the stress sensitivity depended on the perpendicular stress. The biaxially calibrated Barkhausen noise method was applied to residual stress measurements of welded steel tubes. The results were compared with X-ray diffraction and hole drilling results. In the axial direction of the tube all methods produced consistent results. In the hoop direction of the tube Barkhausen noise and X-ray diffraction provided similar results. They were different from those obtained with the hole drilling method.

Quantification of the Barkhausen noise method for the evaluation of time-dependent degradation

The Barkhausen noise (BN) method has long been applied to measure the bulk magnetic properties of magnetic materials. Recently, this important nondestructive testing (NDT) method has been applied to evaluate microstructure, stress distribution analysis, fatigue, creep and fracture characteristics. Until now the BN method has been used only qualitatively in evaluating the variation of BN with variations in material properties. For this reason, few NDT methods have been applied in industrial plants and laboratories. The present investigation studied the coercive force and BN while varying the microstructure of ultrafine-grained steels and SA508 cl.3 steels. This variation was carried out according to the second heat-treatment condition with rolling of ultrafine-grained steels and the simulated time-dependent degradation of SA 508 cl.3 steels. An attempt was also made to quantify BN from the relationship between the velocity of magnetic domain walls and the retarding force, using the coercive force of the domain wall movement. The microstructure variation was analyzed according to time-dependent degradation. Fracture toughness was evaluated quantitatively by measuring the BN from two intermediary parameters; grain size and distribution of nonmagnetic particles. From these measurements, the variation of microstructure and fracture toughness can be directly evaluated by the BN method as an accurate in situ NDT method.

Vibratory Stress Relieving Treatment of Welded Steel Components Studied by Barkhausen Noise Method and X-Ray Diffraction

In this study the effectiveness of vibratory stress relieving (VSR) treatment on the residual stresses of axially welded steel tubes made of mild steel was investigated. Residual stresses of the tubes were measured before and after the VSR treatment by Barkhausen noise and X-ray diffraction. Slight, inhomogeneous stress reduction was observed in some of the tubes in the vicinity of the weld seam. Despite of this slight stress reduction, the VSR treated tubes distorted approximately the same amount as untreated tubes during machining. The mechanism behind the observed stress reduction is discussed.

Residual Stress Measurements with Barkhausen Noise Method in Pipelines and Gas-Turbine Details

Residual stress determination in pipelines and critical gas-turbine parts with the help of non-destructive methods is a current problem. In this work we present the results of the residual stress measurements obtained by the Barkhausen method using the RollScan 200-1.

Characterisation of Residual Stress Relaxation in Fatigue Loaded Welded Joints by X-Ray Diffraction and Barkhausen Noise Method

The fatigue behaviour of welded joints is dependent on the weld geometry, its microstructure, the cyclic material properties of the different weld zones and the magnitude and relaxation behaviour of residual stresses. The degree of plastic deformation and the quasi-static residual stress relaxation in the weld was simulated by a FEM-model and coincided well with the residual stresses measured by X-ray diffraction. Under fatigue loading, an advancing residual stress relaxation in the weld is accompanied by a characteristic change in the micromagnetic parameters resulting from the Barkhausen noise measurements. Using a multiparameter regression approach, the problem of ambiguity of micromagnetic parameters can be solved and the micromagnetic testing method can be used for the residual stress determination in welded joints. The results indicate that a characteristic change of the residual stresses and in the behaviour of the micromagnetic parameters shortly before failure of the welded joint can be used as an indicator of severe fatigue damage within the weld.

Detection of fabrication stresses by the Barkhausen noise method : 38843 Karjalainen, L.P.; Rautioaho, R.H. The Effects of Fabrication Related Stresses on Product Manufacture and Performance, Cambridge (United Kingdom), 23–25 Sep. 1985. pp. 149–161. Edited by J.F. Alder. The Welding Institute (1987)

Detection of fabrication stresses by the Barkhausen noise method : 38843 Karjalainen, L.P.; Rautioaho, R.H. The Effects of Fabrication Related Stresses on Product Manufacture and Performance, Cambridge (United Kingdom), 23–25 Sep. 1985. pp. 149–161. Edited by J.F. Alder. The Welding Institute (1987)

Evaluating heat treatment defects, grinding burns and stress in steels by the Barkhausen noise method : 39655 Titto, K.; Karvonen, I. Proceedings of the 4th European Conference on Non-Destructive Testing, London (United Kingdom), 13–17 Sep. 1987. Vol. 3, pp. 1894–1903. Pergamon Press, 3173 pp. (1988)

Evaluating heat treatment defects, grinding burns and stress in steels by the Barkhausen noise method : 39655 Titto, K.; Karvonen, I. Proceedings of the 4th European Conference on Non-Destructive Testing, London (United Kingdom), 13–17 Sep. 1987. Vol. 3, pp. 1894–1903. Pergamon Press, 3173 pp. (1988)