Propagation Of Magnetoelastic Waves Research Articles

Propagation of Magnetoelastic Shear Wave in an Initially Stressed Inhomogeneous Composite-Layered Structure with an Imperfect Interface

Propagation of Magnetoelastic Shear Wave in an Initially Stressed Inhomogeneous Composite-Layered Structure with an Imperfect Interface

Modelling of coupled magnetoelastic waves in structure containing thin antiferromagnetic films on an elastic substrate

In this work we present a model explaining the properties of magnetoelastic waves propagation in the heterostructure containing an antiferromagnetic layer on a non-magnetic elastic substate. Horizontally polarized shear surface waves (SH-waves) propagating in thin film are Love waves. The dispersion characteristic of magnetoelastic waves in such structure was obtained, and the effect of variation of the thickness of the antiferromagnetic layer and the external magnetic field on the frequency of the magnetoelastic resonance was also studied. It was found that an increase in the magnetic field magnitude leads to the increase in the magnetoelastic resonance frequency, and, on the contrary, with an increase in the thickness of the AFM layer the magnitude of the magnetoelastic resonance frequency decreases. The obtained results can be used to develop devices for generating and processing signals in the GHz and THz frequency ranges.

Управление свойствами магнитоупругих волн в слоистых антиферромагнитных гетероструктурах

In this work we present a model explaining the properties of magnetoelastic waves propagation in the heterostructure containing an antiferromagnetic layer on a non-magnetic elastic substate. The dispersion characteristic of magnetoelastic waves in such structure was obtained, and the effect of variation of the thickness of the antiferromagnetic layer and the external magnetic field on the frequency of the magnetoelastic resonance on the elastic structure was also studied. It was found that an increase in the magnetic field magnitude leads to the increase with pressure of the magnetoelastic resonance frequency, and, on the contrary, with an increase in the thickness of the AFM layer the magnitude of the magnetoelastic resonance frequency decreases. The results obtained can be used to create devices for generating and processing signals in the gigahertz and terahertz frequency ranges.

Analysis of the elasto-magnetic wave propagation in a smart magnetostrictive actuator using a mesh-free method

This work aims to propose an implicit algorithm for solving the magnetoelastic wave propagation in a magnetostrictive actuator. This algorithm is built by combining meshless methods with the Newmark implicit time scheme. The mathematical formulation of vibrations of the actuator is performed by modeling the experimental actuator device by a monodimensional magnetostrictive cylindrical rod attached to an elastic spring, subjected to an axial magnetic field. The formulation of the problem is carried out using the rod model. The study is carried out taking into account mechanical and magnetic effects described by a linear model of strain-stress magnetoelastic relations, whose coefficients depend on the square of the magnetic field, elastic, magnetostrictive, and magnetoelastic characteristics of the elastomagnetic material of which the rod is made. The dynamic equation which describes the magnetoelastic wave propagation in the actuator is obtained by applying the Lagrangian formalism based on the least action principle. The wave propagation is governed by a spatio-temporal partial differential equation whose coefficients are a function of on elastic, magnetostrictive, and magnetic characteristics and implicitly depends on time. The resolution of the dynamic equation is made by adopting two numerical approaches developed by combining the mesh-free collocation methods, the Moving Least Squares (MLS), and the Radial Point Interpolation Method (RPIM) with the Newmark implicit scheme temporal integration. By performing the spatial discretization of the displacement, we obtain a system of linear second-order ordinary differential equations (ODEs), then transform it into a system of first-order ordinary differential equations after integrating Newmark’s implicit time scheme. A comparison of results computed by the proposed numerical approaches RPIM and MLS with experimental data available in the literature is presented. The stability and the solutions qualities of two meshless methods, RPIM and MLS, are also studied. The influence of magnetical and mechanical parameters as well as the coupling coefficients on the performance of the magnetostrictive actuator is also made.

Hypersonic magnetoelastic waves in inhomogeneous structures

This work focuses on the propagation of surface magnetoelastic waves in a inhomogeneous structure containing ferromagnetic layer of smooth and slowly variable thickness. The dispersion relation of magnetoelastic waves and the wave attenuation due to the thickness variation in the studied structure were analytically obtained. We found that the magnetoelastic resonance frequency is changed at different positions in this structure. Then proposed the idea of modifying the magnetic field to control the magnetoelastic resonance region, and finally considered the possible applications of this structure for signal processing.

Interaction of magnetoelastic shear waves with a Griffith crack in an infinite strip

In this research paper, the diffraction of a Griffith crack, situated in an infinite strip of finite thickness, due to magnetoelastic shear wave propagation has been analyzed. The effect of magnetic field on the Griffith crack interaction has been studied. Fourier transform is used to reduce the mixed boundary value problem to the dual integral equations. Finally, with the help of Abel’s transform the integral equations have been converted to Fredholm integral equation of 2nd kind. Fox and Goodwin method is used to solve the integral equation numerically. The analytical expression of Stress Intensity Factor at the crack tip has been illustrated graphically for the cases with magnetic effect and without magnetic effect.

Analysis on the propagation of Griffith crack in a magnetoelastic self-reinforced strip subjected to moving punch of constant load

The present study analysed the characteristics of a moving Griffith crack in a self-reinforced strip of finite thickness and infinite extent with the moving parallel punches of constant load acting on the boundaries of the strip at both sides due to the propagation of magnetoelastic plane waves under mechanical point loading. With the aid of integral transform technique, problem has been reduced to the pair of simultaneous singular integral equations with Cauchy-type singularities. The point load at the edge of the moving crack is considered in terms of Dirac delta function, and the expression of stress intensity factor (SIF) at the crack tip with constant point loading has been established in closed form by using the well-known properties of Hilbert transformation. Moreover, some of the special cases have been deduced from the obtained expression of SIF for the force of constant intensity, without punch pressure and anisotropy in the considered strip. Numerical computations and graphical demonstrations have been carried out to observe the profound effect of magnetoelastic coupling parameter, punch pressure, crack length, distinct positions of point load and the velocity of crack associated with magnetoelastic plane wave on SIF for self-reinforced materials and isotropic material strip. A comparative study of SIF at the tip of moving crack has been made for the self-reinforced and isotropic materials to highlight some of the important peculiarities of the problem.

Распростронение магнитоупругих волн в периодической среде

Распростронение магнитоупругих волн в периодической среде

Propagation and reflection of magneto-elastic plane waves at the free surface of a rotating micropolar fibre-reinforced medium with voids

Propagation and reflection of magneto-elastic plane waves at the free surface of a rotating micropolar fibre-reinforced medium with voids

Extended thermodynamics, effective elastic coefficients and electromagnetoelastic waves in superconducting layer

The paper deals with the analysis of an influence of the thermal field and its relaxation properties on the compressional and flexural magnetoelastic waves propagation in a vibrating superconducting layer. The investigations have been confined only to the vortex elastic field in the type-II superconductor. The description is based on the extended thermodynamical model of interactions. Contrary to the existing dynamical descriptions of electromagnetothermoelastic interactions in solids and/or in the magnetic vortex field of elastic character in the type-II superconductor, the influence of the thermal field on the electromagnetoelastic field (or electromagnetoelastic waves in such a medium) has been considered by the use of the effective elastic coefficients dependent on temperature and the relaxation time of the thermal field in low temperatures.

Propagation and dispersion of shock waves in magnetoelastic materials

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into an acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Finally, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker’s asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot’s gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

Pressure anisotropy and small spatial scales induced by velocity shear.

By including the full pressure tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes the initial isotropic pressure nongyrotropic. This is distinct from the usual gyrotropic anisotropy related to the fluid compressibility and usually accounted for in double-adiabatic models. We determine the time evolution of the pressure agyrotropy and discuss how the propagation of "magnetoelastic perturbations" can affect the pressure tensor anisotropization and its spatial filamentation, which are due to the action of both the magnetic field and the flow strain tensor. We support this analysis with a numerical integration of the nonlinear equations describing the pressure tensor evolution.

Modeling of magnetoelastic shear waves due to point source in a viscoelastic crustal layer over an inhomogeneous viscoelastic half space

In the present study, propagation of magnetoelastic shear wave due to a momentary point source in a viscoelastic crustal layer over inhomogeneous viscoelastic half space has been discussed. Green’s function technique and Fourier transform along with method of successive approximation are used to find the closed-form solutions for displacement and generalized shear wave period equation. Attenuation of the resultant shear wave is computed and effects of magnetic field, width of the layer, complex wave number, viscosity, and inhomogeneity parameters are distinctly marked on dissipation curves using two-dimensional and surface plots. It is found that effect of layer’s magnetoelastic coupling parameter on attenuation pattern of shear wave is just the reverse of half space magnetoelastic coupling parameter. Similarly, internal friction of layer has somewhat different effect on shear wave angular frequency than lower half space viscosity. Certain published results are also derived as special cases to the present study.

The influence of hydrostatic stress on the frequency equation of flexural waves in a magnetoelastic transversly isotropic circular cylinder

In this paper, we investigated the influence of initial stress on the frequency equation of flexural waves in a transversely isotropic circular cylinder permeated by a magnetic field. The problem is represented by the equations of elasticity taking into account the effect of the magnetic field as given by Maxwell's equations in the quasi-static approximation. The free stress conditions on the inner and outer surfaces of the hollow circular cylinder were used to form a frequency equation in terms of the wavelength, the cylinder radii, the initial stress and the material constants. The frequency equations have been derived in the form of a determinant involving Bessel functions and its roots given the values of the characteristic circular frequency parameters of the first three modes for various geometries. These roots, which correspond to various modes, have been verified numerically and represented graphically in different values for the initial stress. It is recognized that the flexural elastic waves in a solid body propagated under the influence of initial stress can be differentiated in a clear manner from those propagated in the absence of an initial stress. We also observed the initial stress has a great effect on the propagation of magnetoelastic flexural waves. Therefore this research is theoretically useful to convey information on electromagnetic properties of the material: for example through a precise measurement of the surface current induced by the presence of the magnetic field.

Actuation, propagation, and detection of transverse magnetoelastic waves in ferromagnets

We study propagation of ultrasonic waves through a ferromagnetic medium with special attention to the boundary conditions at the interface with an ultrasonic actuator. In analogy to charge and spin transport in conductors, we formulate the energy transport through the system as a scattering problem. We find that the magneto-elastic coupling leads to a non-vanishing magnetic (elastic) energy accompanying the acoustic (spin) waves with a resonantly enhanced effect around the anti-crossing in the dispersion relations. We demonstrate the physics of excitating magnetization dynamics via acoustic waves injected around the ferromagnetic resonance frequency.

Propagation of magnetoelastic shear waves in an irregular self-reinforced layer

The propagation of horizontally polarised shear waves in an internal irregular magnetoelastic self-reinforced stratum which is sandwiched between two semi-infinite magnetoelastic self-reinforced media is studied. Two shapes of irregularities on the interface of layer and lower semi-infinite media are considered, namely rectangular and parabolic. The dispersion equation is obtained in closed form. The combined effects of reinforcement, magnetic field and irregularity are also studied. Some important features of the results are highlighted. It is also observed that the dispersion equation is in agreement with the classical Love-type wave equation for an isotropic layer sandwiched between two isotropic half-spaces in the absence of reinforcement, magnetic field and irregularity.

Effect of point source and heterogeneity on the propagation of magnetoelastic shear wave in a monoclinic medium

This paper stands to investigate the possibility of propagation of SH waves due to a point source in a magnetoelastic monoclinic layer lying over a heterogeneous monoclinic half-space. The heterogeneity is caused by consideration of quadratic variation in rigidity. The methodology employed combines an efficient derivation for Green’s functions based on algebraic transformations with the perturbation approach. Dispersion equation has been obtained in the closed form. The dispersion curves are compared for different values of magnetoelastic coupling parameters and inhomogeneity parameters. It is found that as heterogeneity parameters and magnetoelastic coupling parameters increases, the phase velocity increases for both isotropic and monoclinic cases but the increase is more prominent in the monoclinic case. In the isotropic case, when heterogeneity and magnetic field are absent, the dispersion equation is matched with the classical SH wave equation.

Effect of Point Source, Self-Reinforcement and Heterogeneity on the Propagation of Magnetoelastic Shear Wave

This paper investigates the propagation of horizontally polarised shear waves due to a point source in a magnetoelastic self-reinforced layer lying over a heterogeneous self-reinforced half-space. The heterogeneity is caused by consideration of quadratic variation in rigidity. The methodology employed combines an efficient derivation for Green’s functions based on algebraic transformations with the perturbation approach. Dispersion equation has been obtained in the closed form. The dispersion curves are compared for different values of magnetoelastic coupling parameters and inhomogeneity parameters. Also, the comparative study is being made through graphs to find the effect of reinforcement over the reinforced-free case on the phase velocity. It is observed that the dispersion equation is in assertion with the classical Love-type wave equation in the absence of reinforcement, magnetic field and heterogeneity. Moreover, some important peculiarities have been observed in graphs.

Magnetoelastic surface waves in auxetic structure

In modern technologies searching materials of peculiar features is of a fundamental interest for many researchers and engineers. Negative Poisson's ratio materials and structures expand transversely when stretching axially. Nowadays, there is an increasing interest in the development of these novel materials called auxetics. We are interested not only in their mechanical properties, but also in their interaction with external physical fields, e.g. electromagnetic field. It is expected that magnetoelastic surface waves propagation has essential meaning in many other physical and biomechanical applications. The paper aims at investigating propagation of magnetoelastic surface waves along an auxetic elastic halfspace in the presence of an external magnetic field of various orientations related to the limiting plane. Dispersion and existence conditions of those waves have been calculated and analyzed in order to present new features of described interactions. It has occurred that the dispersion properties in the case of the Rayleigh-like magnetoelastic surface waves are significantly different for the auxetic material compared to materials of positive Poisson's ratio.