Barkhausen Effect and Emission of Elastic Waves Under Remagnetization of Ferromagnets

The traditional acoustic emission (AE) method implementation requires applying an external load to the controlled object. Considering that the load required for the small defects’ propagation can be much higher than the optimal loading modes of the object of control, the application of this approach in the practice of AE diagnostics is limited. To avoid this, in ferromagnetic materials, AE can be excited by an external magnetic field caused by the spontaneous movement of the walls of magnetic domains—the Barkhausen effect. Thus, by combining the signals of magnetoelastic AE with known physical phenomena, it is possible to create techniques for effectively detecting and quantifying the degree of degradation of structural materials, for example, under the influence of hydrogen-mechanical factors. The nature of the Barkhausen effect, its practical application, and separate theoretical approaches to the interpretation of physical essence are described in this chapter of the monograph. The most common models of magnetoelastic AE signals, which are caused by Barkhausen jumps, and the main relations of the theory of magnetoelasticity are analyzed.