Papers by Keyword: Barkhausen Noise

Abstract: The effect of mechanical stress on Barkhausen noise from 45-permalloy plate is reported for as-rolled plate and plates which are annealed at various temperatures up to 1000 K. The data are compared with data of magnetic permeability, coercive force and Vickers hardness. The Barkhausen noise energy detected has been found to increase linearly with nominal stress. The larger the annealing temperature, the less the rate of increase was observed. On the other hand, the magnetic permeability has been found to decrease linearly with nominal stress in a small stress region. Overall features are explained qualitatively by a model in which tensile stress makes the number of effective pinning sites which have appropriate activation energies for discontinuous motion of domain wall more, while annealing process makes just the number of pinning sites such as defects and grain boundaries less.

Abstract: The use of magnetic Barkhausen Noise Analysis (BNA) has been proven to be an effective tool for the non-destructive detection of microstructural anomalies in ferrous materials. Used as an in-process tool for the detection of grinding burn, heat treat defects and stresses, BNA is a quick comparative and quantitative alternative to traditional destructive methods. Applications of BNA as a quality control tool in gear production have existed for nearly two decades. This paper presents examples that demonstrate how BNA is used to evaluate changes in microstructural properties. Quantitative results correlate BNA test values to X-Ray diffraction values for the detection of changes in surface residual stress. Other quantitative analysis correlates BNA test values to surface hardness values for the detection of re-tempering burn. Qualitative results correlate BNA test values to acid etch patterns/colors for the detection of grinding burn defects. Robotically automated systems can test gear teeth and provide immediate feedback for process control and quality assurance.

Abstract: The objective of this study is to estimate the feasibility of advanced nondestructive method(X-ray diffraction, AE(acoustic emission) and BN(barkhausen noise)measurement application for fatigue life evaluation of the high-temperature pipeline steel such as main steam pipe etc. in power plant. In this study, various nondestructive tests using various types of specimen simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages such as 1/4, 1/2 and 3/4 of fatigue life, respectively. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the variation of the full width at half maximum intensity decreased in proportion to the increase of fatigue life ratio. And also, AE and BN signal due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.

Abstract: The potentialities of using the magnetic Barkhausen noise measurement in characterization of metallurgical transformations have been highlighted in multi-phase High Strength (HS) steels. This kind of steels are composed of different metallurgical constituents, such as ferrite, bainite, martensite or residual austenite. Recently, we found that it was possible to assess the proportion of phases in ferrite-martensite steels and in industrial Dual-Phase steels too. In this work, we show that the Barkhausen noise measurements can be also suitable to follow bainitic transformation in a TRIP steel.

Abstract: Barkhausen noise properties of amorphous and nanocrystallized FINEMET type soft magnetic materials are investigated. It is obtained that the amorphous-nanocrystalline tranformation has a well observable effect on both the root main square, RMS, values and the critical exponents of the probability distributions of peak heights and durations.

Abstract: The micromagnetic measurement method is a well known technique for a qualitative estimation of residual stresses in ferromagnetic materials. The application due to the advantages of a fast and manageable use is hindered by the high complexity of the calibration procedure for the quantitative residual stress determination when additionally a changing microstructure influences the measured signals. Therefore basic investigations were performed for the residual stress determination of welded joints by the micromagnetic method. A multi-parameter approach by using different micromagnetic techniques was evaluated by a linear regression analysis. For each structural steel a regression polynomial can be calculated for the residual stress determination of differently welded specimens. The accuracy of the prediction depends on the magnetization direction. The experimental results show, that this strategy enables a useful possibility of an easier method for the determination of residual stresses in welded joints.

Abstract: In this work, we show that the measurement of the Barkhausen noise allows the residual stresses in each of the two phases of ferrite-martensite steels to be characterized. We have first studied the effect of a tensile and a compressive stress on the Barkhausen noise signature. We observed that for a ferrite-martensite steel, the application of a tensile stress increases the Barkhausen activity of the martensite and ferrite phases, whereas a compressive one reduces it. In a second time, we induced residual stresses by applying a plastic deformation to ferrite-martensite steels. After a tensile plastic deformation, we observed that (i) compressive residual stresses appear in ferrite, and (ii) tensile residual stresses appear in martensite. An opposite behavior is observed after a compressive plastic deformation. These results show that the Barkhausen noise measurement makes it possible to highlight in a nondestructive way the distribution of the stresses in each of the two phases of a ferrite-martensite steel. This result could be used to characterize industrial Dual- Phases steels that are plastically deformed during mechanical processes.

Abstract: Magnetic Barkhausen noise measurements have been carried out to characterize ferritemartensite duplex microstructures and industrial Dual-Phase steels. We have first studied ferritemartensite duplex steels, for which the volume fraction and the carbon content of martensite were higher than for industrial Dual-Phase steels. We found linear evolutions between ferrite peak parameters and its proportion. We applied these results to industrial Dual-Phase steels and show that Barkhausen noise measurement can be successfully used for Dual-Phase steels characterization, and in particular for assessment of ferrite proportion.

Abstract: Magnetic Barkhausen noise measurement (MBN) is a relatively new non-destructive detection technique. Its working principle is based on Barkhausen discontinuities or noise when a ferromagnetic material is subjected to a varying magnetic field. MBN is being used to characterise the stress state of a ferritic stainless steel (AISI 430). Other magnetic parameters such as saturation induction (BMax), remnant induction (BR), coercive field (HC) and maximal relative permeability (PMax) derived from the hysteresis loop have also been used to support the results achieved using MBN. Microstructural changes due to cold working and heat treatments were characterized by the applied magnetic measurements. The MBN technique was proved to be a useful non-destructive and quantitative method for microstuctural investigation of the investigated ferritic stainless steel.