The following paper presents the basis of a Rayleigh magnetic hysteresis model and the examples of its application for modeling the magnetic characteristics of ferromagnetic materials: ferrites and steels. The presented model allows one to simulate the shape of a magnetic hysteresis loop of the material for the given value of the magnetizing field in the so-called Rayleigh region, as well as to calculate basic magnetic parameters of the material like coercive field, magnetic remanence, and power loss. Four different ferromagnetic materials (two ferrites and two alloy steels) were chosen for the investigation. Each material was investigated within the range of low magnetizing fields, corresponding to the Rayleigh region. On the basis of obtained results, modeling of magnetic characteristics of the investigated materials was performed. Moreover, the range of magnetizing field where the Rayleigh model can be applied for these materials was investigated based on correlation coefficient between experimental results and modeling.

Abstract. Paper presents the frame-shaped cores based methodology of testing of magnetoelastic characteristics of energetic steels such as X30Cr13 steel, subjected to tensile stresses. In presented method, the magnetic circuit of the sample is closed. For this reason, the results of magnetoelastic investigation are independent of the shape of the sample. To validate the proposed method, the influence of tensile stresses on B(H) hysteresis loop of X30Cr13 martensitic corrosion resistant steel was carried out. On the base of these result, clear criteria for non-destructive assessment of mechanical stresses in the material were determined.Keywords: magnetoelastic effect, corrosion resistant steel, stress assessment. IntroductionUnder the influence of mechanical stresses, the shape of B(H) magnetic hysteresis loop changes significantly for both crystalline [1] and amorphous [2] magnetic materials. This effect is commonly known as magnetoelastic effect [3,16]. In spite of the fact that changes of flux density B under stresses are most significant for high permeability amorphous and nanocrystalline alloys [4,5,6], the magnetoelastic effect is also observed in steels [7,8,9]. As a result, measurements of stress-induced changes of shape of hysteresis loop of steel, creates the possibility of non-destructive assessment of mechanical stresses generated during the use mechanical component. Magnetoelastic-effect based non-destructive testing of corrosion resisting steels can be considered only for the martensitic steels, such as X30Cr13 steel. Austenitic steels are non-magnetic, however, under specified mechanical stresses austenite may be conversed to martensite [10,11,12]. This phenomenon is also very interesting from the non-destructive testing point of view, but its principle is different than magnetoelastic effect in martensitic steels.Martensitic corrosion resisting X30Cr13 steel exhibits good resistance to the corrosive effect of salt water, weather and various corrosion agents. Moreover, this steel

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