Interaction of a finite crack with shear waves in an infinite magnetoelastic medium

The aim of this paper is to investigate the interaction of a finite crack with shear waves in an infinite magnetoelastic medium. Fourier integral transformation is applied to convert the boundary value problem for a homogeneous, isotropic elastic material to the Fredholm integral equation of second kind. The integral equation is solved by the perturbation method and the effect of magnetic field interaction on the crack is discussed. The stress intensity factor at the crack tip is determined numerically and plotted for low frequencies. Moreover, shear stress outside the crack, crack opening displacement, and crack energy are evaluated and shown by means of graphs.

MAGNETOELASTIC ELECTROMAGNETIC ACOUSTIC TRANSFORMATION. PART VI

In the case of EMAT using overhead transducers, a high-frequency alternating and strong polarizing magnetic fields jointly act on the magnetoelastic medium. These fields can be positioned at different directions to each other. The article analyzes the situation when the polarizing field, located along the interface of the media and the normal component of the emitter variable field are orthogonally related. That is, the classic Wiedemann effect is implemented in EMAT. It has been shown that the Wiedemann effect in EMAT contributes primarily to the generation of shear waves. The generation of longitudinal waves is secondary and less efficient. About an order of magnitude less In fact, the Wiedemann effect can only be observed (compared to the Joule effect) for the materials with low conductivity and for the ferrodielectrics. Increasing the efficiency of the method is possible by increasing the frequency of the current in the transducer. When the conductivity and frequency properly seltcted, the efficiency of the method can compete with EMAT performed by means of the Joule effect.

Green’s Function of Magnetoelastic Waves

The matrix (5x5) Green's function of magnetoelastic waves in an isotropic magnetoelastic medium taking into account the dipole-dipole interaction has been derived. The imaginary parts of diagonal and off-diagonal elements of the Green's function in the crossing resonance of spin and longitudinal elastic waves has been investigated. It is shown that under changing the angle of wave propagation θ the amplitudes of Green functions change drastically due redistribution of energy between the magnetic and elastic oscillation. Approximate expressions for the dependence of the widths of the gaps in the spectrum on the angle θ have been also derived.