Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magn... more Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magnetic investigation of structural low-carbon steel subjected to uniaxial plastic tension. Scattering of the measured magnetic parameters was substantial within the Lüders band region with stabilization at higher strains. Compressive residual stresses in the deformation direction formed a hard magnetization axis with intriguing two-phase remagnetization. The magnetic parameters had the highest sensitivity to strain in this direction. They changed as cos2 with rotation to the perpendicular easy magnetization axis, where the magnetic sensitivity was the lowest. The relation between the deformed steel microstructure (dislocation and residual stress patterns) and the obtained magnetic behaviour is interpreted. The applicability of the examined techniques for the non-destructive characterization of steel degradation is discussed.
The paper investigates applicability of the Barkhausen noise technique as a non-destructive testi... more The paper investigates applicability of the Barkhausen noise technique as a non-destructive testing method and its correlation with the magnetic hysteresis measurement. The hysteresis and the Barkhausen noise experiments were performed at laboratory and industrial configurations on a model series of open flat samples plastically deformed by mechanical tension. The sample magnetic field was measured with the help of a
Structural variation in a series of cast iron samples was non-destructively characterized by mean... more Structural variation in a series of cast iron samples was non-destructively characterized by means of sets of magnetic minor hysteresis loops. The flat samples were magnetized by an attached yoke, and reliable parameters were obtained from the series of minor loops, without magnetic saturation of the samples. It was found, that some magnetic quantities, well known to be closely connected
Degradation of a low-carbon steel with plastic tension has been investigated after unloading by m... more Degradation of a low-carbon steel with plastic tension has been investigated after unloading by magnetic methods (hysteresis and Barkhausen noise (BN) emission). The measurements were done with magnetization in parallel as well as in perpendicular direction to the previous elongation. The dislocation structure formation was checked by transmission electron microscopy (TEM). Evolution of magnetic parameters with applied strain was examined and applicability of magnetic methods for non-destructive testing (NDT) is discussed. It was concluded that the change of the two-peak profile of BN envelope and differential permeability (leading to hysteresis loop bulging) in the parallel direction to the one-peak profile in the perpendicular direction is due to the deformation-driven accumulation of residual stresses.
This work describes a specially designed setup for magnetic hysteresis and Barkhausen noise measu... more This work describes a specially designed setup for magnetic hysteresis and Barkhausen noise measurements. The setup combines two main elements: an improved fast algorithm to control the waveform of magnetic induction and simultaneous direct determination of the magnetic field. The digital feedback algorithm uses only the previous measurement cycle to correct the magnetization voltage without any additional correlation parameter; it usually converges after several tens of cycles. The magnetic field is measured at the sample surface using a vertically mounted array of sensitive Hall sensors. Linear extrapolation of the tangential field profile to the sample surface determines the true waveform of the magnetic field. This unique combination of physically based control for both parameters of the magnetization process provides stable and reliable results, which are independent of a specified experimental configuration. This is illustrated for the industrially attractive measurements of non-oriented electrical steels with a 50 Hz sinusoidal induction waveform.
Surface decarburization of steel was non-destructively and quantitatively investigated by magneti... more Surface decarburization of steel was non-destructively and quantitatively investigated by magnetic hysteresis. Flat samples were prepared from spring steel 54SiCr6 and decarburized layers of different thickness were produced on their surfaces by annealing at 800°C in air for 1, 4, 8 and 20h. Three types of treatment were applied on different samples in order to remove the simultaneously appearing surface oxides. The decarburized layers were examined magnetically by hysteresis loops measurements and the results were related to their optically determined depths. The magnetic measurements showed high sensitivity with respect to free ferrite and mixed ferrite/pearlite layers detection even without removal of the oxide layer. The free ferrite layers were easily and quantitatively detected by minor loops measurements with low field amplitude.
ABSTRACT Structural and magnetic properties of (NdBa)MnO3 thin films grown on several perovskite ... more ABSTRACT Structural and magnetic properties of (NdBa)MnO3 thin films grown on several perovskite substrates by pulsed laser deposition are presented. A high crystal quality epitaxial film with smooth surface and low level of internal strain may be grown up to thicknesses of 70 nm. The in-plane distortion of the film lattice by the substrate-introduced compressive strain promotes corresponding changes in the out-of-plane lattice constant, following the volume-preserving dilation. The films under tensile strain are growing totally relaxed. Different oxygenation conditions during depositions induce correlated changes of structural and magnetic properties of the material. The temperature of ferromagnetic transition of the films is around 100 K and increases with expansion of the unit cell. The magnetic moment in saturation is usually higher along the longest lattice constant of the film. An increase of the bi-axial compressive strain introduced by the substrate results in a rapid increase of the magnetic moment of the films. The observed effects may be explained by a high level of local distortions due to difference in the ionic radii of Nd and Ba.
Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magn... more Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magnetic investigation of structural low-carbon steel subjected to uniaxial plastic tension. Scattering of the measured magnetic parameters was substantial within the Lüders band region with stabilization at higher strains. Compressive residual stresses in the deformation direction formed a hard magnetization axis with intriguing two-phase remagnetization. The magnetic parameters had the highest sensitivity to strain in this direction. They changed as cos2 with rotation to the perpendicular easy magnetization axis, where the magnetic sensitivity was the lowest. The relation between the deformed steel microstructure (dislocation and residual stress patterns) and the obtained magnetic behaviour is interpreted. The applicability of the examined techniques for the non-destructive characterization of steel degradation is discussed.
The paper investigates applicability of the Barkhausen noise technique as a non-destructive testi... more The paper investigates applicability of the Barkhausen noise technique as a non-destructive testing method and its correlation with the magnetic hysteresis measurement. The hysteresis and the Barkhausen noise experiments were performed at laboratory and industrial configurations on a model series of open flat samples plastically deformed by mechanical tension. The sample magnetic field was measured with the help of a
Structural variation in a series of cast iron samples was non-destructively characterized by mean... more Structural variation in a series of cast iron samples was non-destructively characterized by means of sets of magnetic minor hysteresis loops. The flat samples were magnetized by an attached yoke, and reliable parameters were obtained from the series of minor loops, without magnetic saturation of the samples. It was found, that some magnetic quantities, well known to be closely connected
Degradation of a low-carbon steel with plastic tension has been investigated after unloading by m... more Degradation of a low-carbon steel with plastic tension has been investigated after unloading by magnetic methods (hysteresis and Barkhausen noise (BN) emission). The measurements were done with magnetization in parallel as well as in perpendicular direction to the previous elongation. The dislocation structure formation was checked by transmission electron microscopy (TEM). Evolution of magnetic parameters with applied strain was examined and applicability of magnetic methods for non-destructive testing (NDT) is discussed. It was concluded that the change of the two-peak profile of BN envelope and differential permeability (leading to hysteresis loop bulging) in the parallel direction to the one-peak profile in the perpendicular direction is due to the deformation-driven accumulation of residual stresses.
This work describes a specially designed setup for magnetic hysteresis and Barkhausen noise measu... more This work describes a specially designed setup for magnetic hysteresis and Barkhausen noise measurements. The setup combines two main elements: an improved fast algorithm to control the waveform of magnetic induction and simultaneous direct determination of the magnetic field. The digital feedback algorithm uses only the previous measurement cycle to correct the magnetization voltage without any additional correlation parameter; it usually converges after several tens of cycles. The magnetic field is measured at the sample surface using a vertically mounted array of sensitive Hall sensors. Linear extrapolation of the tangential field profile to the sample surface determines the true waveform of the magnetic field. This unique combination of physically based control for both parameters of the magnetization process provides stable and reliable results, which are independent of a specified experimental configuration. This is illustrated for the industrially attractive measurements of non-oriented electrical steels with a 50 Hz sinusoidal induction waveform.
Surface decarburization of steel was non-destructively and quantitatively investigated by magneti... more Surface decarburization of steel was non-destructively and quantitatively investigated by magnetic hysteresis. Flat samples were prepared from spring steel 54SiCr6 and decarburized layers of different thickness were produced on their surfaces by annealing at 800°C in air for 1, 4, 8 and 20h. Three types of treatment were applied on different samples in order to remove the simultaneously appearing surface oxides. The decarburized layers were examined magnetically by hysteresis loops measurements and the results were related to their optically determined depths. The magnetic measurements showed high sensitivity with respect to free ferrite and mixed ferrite/pearlite layers detection even without removal of the oxide layer. The free ferrite layers were easily and quantitatively detected by minor loops measurements with low field amplitude.
ABSTRACT Structural and magnetic properties of (NdBa)MnO3 thin films grown on several perovskite ... more ABSTRACT Structural and magnetic properties of (NdBa)MnO3 thin films grown on several perovskite substrates by pulsed laser deposition are presented. A high crystal quality epitaxial film with smooth surface and low level of internal strain may be grown up to thicknesses of 70 nm. The in-plane distortion of the film lattice by the substrate-introduced compressive strain promotes corresponding changes in the out-of-plane lattice constant, following the volume-preserving dilation. The films under tensile strain are growing totally relaxed. Different oxygenation conditions during depositions induce correlated changes of structural and magnetic properties of the material. The temperature of ferromagnetic transition of the films is around 100 K and increases with expansion of the unit cell. The magnetic moment in saturation is usually higher along the longest lattice constant of the film. An increase of the bi-axial compressive strain introduced by the substrate results in a rapid increase of the magnetic moment of the films. The observed effects may be explained by a high level of local distortions due to difference in the ionic radii of Nd and Ba.
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