PSI - Issue 20

Eduard Gorkunov et al. / Procedia Structural Integrity 20 (2019) 4–8 Eduard Gorkunov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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then decreases, reaches zero, and continues decreasing, this time with a negative sign (curve 1 in figure 4a). For the cyclically loaded specimens (curves 2 and 3 in figure 4a), ║ ( Н ) is positive at all the values of magnetic field strength. Note that, as the number of cycles increases, the area of the positive portion of the field dependence of magnetostriction increases, and so does the magnitude of its peak.

Fig. 3. The field dependence of differential magnetic permeability for the specimens tested for the zero-to-tension cycling with different numbers of cycles n : n = 0 (curve 1), n = 30 (2), n = 50 (3), n = 100 (4), and n = 300 (5) thousands. For the unloaded specimen ( n = 0), the transverse magnetostriction ┴ ( H ) first decreases to a minimum with growing magnetic field strength, then increases, reaches zero, and continues increasing with a positive sign (curve 1 in figure 4b). The transverse magnetostriction of the cyclically loaded specimens is negative in the entire range of magnetic field strength variation. The area of the negative portion of the transverse magnetostriction increases with n , and so does the absolute value of its minimum. This behavior of ║ ( Н ) and ┴ ( H ) is inherent in -iron-based magnets affected by compressive stresses, this being indicative of the formation of residual compressive stresses after cyclic loading along the axis of cyclic tension and residual tensile stresses in the transverse direction.

Fig.4. The dependences ║ ( Н ) (a) and ┴ ( H ) (b) for specimens tested for zero-to-tension cycling with different numbers of cycling n : n = 0 (curve 1), n = 30 (2), and n = 100 (3) thousands.