The paper presents the results of multiparameter analysis of Barkhausen noise (BN) signal properties. In addition to the commonly used quantifiers of the BN signal, such as amplitude, integral of the BN envelope or results of pulse count analysis, we propose an additional analysis based on the change in magnetizing current amplitude. As it turns out the character of the change of the BN signal (as a function of the plastic deformation level) measured for various magnetizing currents differs significantly. Being so, a comparison of the results obtained for at least two magnetizing intensities gives a much better description of a plastic deformation level. In addition to that we observe two monotonic changes in the BN signal properties-a systematic shift of the BN signal peak position and the increase in the frequency for which the maximum in the BN FFT spectra occurs.
The paper describes an application of nondestructive volumetric magnetic and ultrasonic techniques for evaluation of the selected mechanical parameter variations of P91 steel having direct influence on its suitability for further use in critical components used in power plants. Two different types of deformation processes were carried out. First, a series of the P91 steel specimens was subjected to creep and second, one to plastic deformation in order to achieve the material with an increasing strain level up to 10%. Subsequently, non-destructive and destructive tests were performed. Magnetic methods based on measurements of magnetoacoustic emission and magnetic hysteresis loop changes as well as the ultrasonic method based on acoustic birefringence measurements, were applied. Finally, the static tensile tests were carried out in order to evaluate the mechanical parameters. It is shown that some relationships between the selected parameters coming from the non-destructive and destructive tests may be formulated.
The magnetic Barkhausen effect is useful for assessing 1D and 2D stress states of ferromagnetic steel objects. However, its extension to technically important materials, such as duplex anisotropic steels, remains challenging. The determination of magnetisation inside the studied object and the electromagnet for various geometries, materials and magnetisation angles is a key issue. Three-dimensional, dynamic finite element analysis has been applied to reproduce time-varying fields inside and outside the prototype of a double-core magnetising setup. Useful relationships between characteristics (peak height and location) and magnetic induction vector have been proposed. The qualitative plausibility of simulation has been validated with an experiment and an analytic formula of skin depth. The angular anisotropy of magnetic Barkhausen effect (MBN) in an isotropic sample has been shown in simulation and confirmed experimentally. The numerical model, despite some limitations, seems to be an efficient tool for calibrating stress/MBN relationships at least in isotropic structural steel components.Keywords Electromagnetic finite element method · Dynamic magnetisation of bulk volume · Eddy currents · Magnetic Barkhausen effect (MBN) B Marek Augustyniak
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