PSI - Issue 40

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A.M. Povolotskaya et al. / Procedia Structural Integrity 40 (2022) 359–364 A.M. Povolotskaya, A.N. Mushnikov / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 3. The field dependence of differential magnetic permeability µ d ( H ) for the specimens plastically deformed to different values of plastic strain ε: 0 (curve 1), 0.75 (2), 1.28 (3), 1.96 (4), 5.01 (5), 7.53 (6), and 10 % (7).

Fig. 4. Major magnetic hysteresis loops for the specimens plastically deformed to different values of plastic strain ε: 0 (curve 1), 0.75 (2), 1.28 (3), 1.96 (4), 5.01 (5), 7.53 (6), and 10 % (7).

The origin of the appearance of the bends of magnetic hysteresis loops and the second peak in positive fields on the µ d ( H ) dependences for plastically deformed specimens is as follows. As noted above, after plastic deformation, residual compressive stresses appear in a significant part of the grains along the loading axis, which cause the formation of a magnetic texture of the “easy magnetization plane” type. In the fields where magnetoelastic energy becomes greater than magnetostatic energy and the magnetic field energy becomes insufficient to keep the magnetization vectors perpendicular to the “easy magnetization plane”, there begin to occur irreversible transitions of 90-degree domain walls to the most favorable energetically easy direction. A similar formation of two peaks in the µ d ( H ) dependences were described in Nichipuruk et al. (2014), Kuleev et al. (2015), Kuleev et al. (2019), Pal’a et al . (2007) for specimens deformed by static uniaxial tension and in Gorkunov et al. (2019), Gorkunov et al. (2021) for specimens subjected to zero-to-tension cyclic loading with an amplitude exceeding the yield stress of the steel under study. Figure 5 shows the corresponding plastic strain dependences of the value of the peak of the differential magnetic permeability in negative fields  d max . With increasing ε, the parameter  d max behaves similarly to the magnetic characteristics shown in Fig. 2. The most intense changes of  d max occur at plastic strains ranging between 0 and about 2 %. The changes with further deformation are insignificant.