Jin-Xi Liu

Interfacial shear horizontal waves in a piezoelectric-piezomagnetic bi-material

The propagation of an interfacial shear horizontal (SH) wave is studied in two bonded semi-infinite materials, one piezoelectric and the other piezomagnetic. Both materials are hexagonal (6 mm) crystals. The dispersion relation is given in an explicit form. Based on the obtained dispersion relationship, conditions for the existence of interfacial SH waves are discussed in detail.

Propagation of Rayleigh-type surface waves in a transversely isotropic piezoelectric layer on a piezomagnetic half-space

Propagation of Rayleigh-type surface waves in a piezoelectric-piezomagnetic layered half-space is investigated. The materials are assumed to be transversely isotropic crystals. The dispersion relations have been numerically derived and computed by considering the coupling piezoelectric and piezomagnetic behaviors. The phase velocities are obtained for four kinds of electric-magnetic boundary conditions at the free surface. The variations of mechanical displacements, electric and magnetic potentials along the thickness direction of the layer are obtained. The effects of different electric-magnetic boundary conditions on the phase velocity and mode shapes of displacements, electric and magnetic potentials have been discussed. The results show that the lowest mode is Rayleigh mode and that the phase velocities of the higher modes tend to the shear wave velocity of the piezoelectric layer as the frequency increases. The electric boundary conditions dominate the phase velocity. The magnetic boundary conditions...

PROPAGATION BEHAVIORS OF SHEAR HORIZONTAL WAVES IN PIEZOELECTRIC-PIEZOMAGNETIC PERIODICALLY LAYERED STRUCTURES

This paper investigates shear horizontal (SH) waves propagating in a periodically layered structure that consists of piezoelectric (PE) layers perfectly bonded with piezomagnetic (PM) layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.

A study of the band structures of elastic wave propagating in piezoelectric/piezomagnetic layered periodic structures

This paper is concerned with wave propagation and localization in piezoelectric (PE) and piezomagnetic (PM) layered periodic structures. Both normal and oblique propagation of waves are considered. The materials are assumed to be transversely isotropic. Wave behaviors are analyzed by calculating the dispersion curves, localization factors and response spectra using the transfer matrix and/or the stiffness matrix methods. The results show that all these quantities can be used to characterize the band structures. Frequency passbands and band gaps exist in PE/PM periodic layered structures. The width of the gaps is determined by the differences between material constants of each constituent in PE/PM composites. The bigger the difference is, the wider the gap is. Most energy is carried by the transmitted waves which are of the same mode as the incident wave. However, the transmission coefficients of the quasi-shear or quasi-pressure waves arising from wave mode conversion may be relatively large at some particular frequencies in some passbands. Compared to coupled transmitted magnetoacoustic and electroacoustic waves, the transmission coefficients of electric potential and magnetic potential waves are a little bigger. This study is useful for the possible applications of PE/PM materials in the fabrication of high frequency acoustic resonance devices.

Propagation of shear horizontal surface waves in a layered piezoelectric half-space with an imperfect interface

We investigate the dispersive behavior of shear horizontal (SH) surface waves propagating in a layered structure consisting of a piezoelectric layer and an elastic half-space, in which the top and bottom of the layer are electrically shorted. The interface between the layer and the half-space is assumed to be imperfect bonding. The degree of imperfection of the interface is described by the so-called shear-lag model. The dispersion equations are expressed in an explicit closed form. The phase velocities are calculated to show the influences of the interfacial imperfection and the material properties of piezoelectric layers on the dispersive characteristics.

Analysis of a monolithic crystal plate acoustic wave filter

We study thickness-shear and thickness-twist vibrations of a finite, monolithic, AT-cut quartz plate crystal filter with two pairs of electrodes. The equations of anisotropic elasticity are used with the omission of the small elastic constant c(56). An analytical solution is obtained using Fourier series from which the resonant frequencies, mode shapes, and the vibration confinement due to the electrode inertia are calculated and examined.

Fracture analysis of bounded magnetoelectroelastic layers with interfacial cracks under magnetoelectromechanical loads: Plane problem

Fracture behaviors of multiple interfacial cracks between dissimilar magnetoelectroelastic layers subjected to in-plane magnetoelectromechanical loads are investigated by using integral transform method and singular integral equation technique. The number of the interfacial cracks is arbitrary, and the crack surfaces are assumed to be magnetoelectrically impermeable. The field intensity factors including stress, electric displacement and magnetic induction intensity factors as well as the energy release rates (ERRs) are derived. The effects of loading combinations, crack configurations and material property parameters on the fracture behaviors are evaluated according to energy release rate criterion. Numerical results show that both negative electrical and magnetic loads inhibit crack extension, and that the material constants have different and important effects on the ERRs. The results presented here should have potential applications to the design of multilayered magnetoelectroelastic structures.

Dynamic stress and electric displacement around a nano-fiber in piezoelectric nanocomposites under electro-elastic waves

In piezoelectric nanocomposites, surface/interface stress and electric displacement have a great effect on the strength of structures. In this work, predicated on nanoscale size-effects, the dynamic stress along the interface of a cylindrical piezoelectric nano-fiber in piezoelectric nanocomposites under electro-elastic waves is studied. The surface/interface model of Gurtin and Murdoch is extended to the case of piezoelectric interface, and the coupling of stress and electric displacement is considered. By introducing a function, the governing equation in piezoelectric materials is decoupled. The displacement and electric potential are expressed by a wave function. The dynamic stress concentration around the nano-fiber is obtained. Through analysis, it is found that the coupling of stress and electric displacement at the surface/interface shows important effect on the dynamic stress and electric displacement around the nano-fiber. The surface/interface effect is also related to the frequency of electro-elastic waves, and the properties of the nano-fiber and the interface. To show the accuracy for certain given parameters, comparison is made with existing results.

Effect of initial stress on propagation behaviors of shear horizontal waves in piezoelectric/piezomagnetic layered cylinders

An analytical approach is taken to investigate shear horizontal wave (SH wave) propagation in layered cylinder with initial stress, where a piezomagnetic (PM) material thin layer is bonded to a piezoelectric (PE) cylinder. Two different material combinations are taken into account, and the phase velocities of the SH waves are numerically calculated for the magnetically open and short cases, respectively. It is found that the initial stress, the thickness ratio and the material performance have a great influence on the phase velocity. The results obtained in this paper can offer fundamental significance to the application of PE/PM composite media or structure for the acoustic wave and microwave technologies.

Surface effect on size-dependent wave propagation in nanoplates via nonlocal elasticity

Within the framework of nonlocal elasticity, the surface layer model is proposed to investigate the wave propagation characteristics in a single-layered nanoplate. The general solutions of nonlocal governing equations are expressed using partial wave technique and the nonclassical boundary conditions are derived. The dispersion relation with the effects of surface and nonlocal small-scale is obtained, and the size-dependent dispersion behaviour is demonstrated. The impacts of surface elasticity, residual surface stress and nonlocal parameter on the dispersion curves of the lowest-order two modes are illustrated. Numerical examples reveal that both the surface effect and nonlocal small-scale effect can obviously decrease the magnitude of phase velocity, and the thinner nanoplate corresponds to the smaller wave velocity and the narrower frequency bandwidth.