Horizontal Surface Waves Research Articles

Shear Horizontal Surface Waves in a Functionally Graded Magneto-Electro-Elastic Half-Space

We investigate the propagation of shear horizontal (SH) surface waves in a functionally graded magneto-electro-elastic half-space with hexagonal (6mm) symmetry. The material properties vary in the direction perpendicular to the free surface. The surface of the half-space is mechanically free, but subjected to four types of electromagnetic boundary conditions. These boundary conditions are electrically open/magnetically closed, electrically open/magnetically open, electrically closed/magnetically open and electrically closed/magnetically closed. The effects of the electromagnetic boundary conditions and the variation of material properties on the propagation characteristics of SH surface waves are analyzed. The results obtained show that except for the electrically open/magnetically closed condition, three sets of other electromagnetic boundary conditions sustain the propagation of SH surface waves. Different from the case in homogeneous materials, the existing SH surface waves in functionally graded half-spaces are dispersive.

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.

Existence of Shear Horizontal Surface Waves in a Magneto-Electro-Elastic Material

The existence of shear horizontal surface waves in a magneto-electro-elastic (MEE) half-space with hexagonal (6mm) symmetry is investigated. The surface of the MEE half-space is mechanically free, but subjected to four types of electromagnetic boundary conditions. These boundary conditions are electrically open/magnetically closed, electrically open/magnetically open, electrically closed/magnetically open and electrically closed/magnetically closed. It is shown that except for the electrically open/magnetically closed condition, the three other sets of electromagnetic boundary conditions allow the propagation of shear horizontal surface waves.

Dynamic crack propagation in a magneto-electro-elastic solid subjected to mixed loads: Transient Mode-III problem

The transient response of a Mode-III crack propagating in a magneto-electro-elastic solid subjected to mixed loads is investigated through solving the corresponding boundary-initial-value problem in both the cracked solid region and the interior fluid region with treatment of electro-magnetically permeable and impermeable crack face conditions in a unified way. The closed-form results for the dynamic field intensity factors are used to evaluate the dynamic energy release rate through the crack-tip dynamic contour integral. The permeability of the interior fluid region relative to the cracked solid region significantly affects the magneto-electro-mechanical coupling coefficient in the Bleustein–Gulyaev wave function and, consequently, the horizontal shear surface wave speed, the dynamic field intensity factors and the dynamic energy release rate. It is revealed from dynamic fracture mechanics analysis that the dynamic energy release rate thus obtained has an odd dependence on the dynamic electric displacement intensity factor and the dynamic magnetic induction intensity factor. It is also found that the horizontal shear surface wave speed provides the limiting velocity for the propagation of a Mode-III crack in a magneto-electro-elastic solid when there is only applied traction loading.

Existence and spectral properties of shear horizontal surface acoustic waves in vertically periodic half-spaces

The paper is concerned with the propagation of shear horizontal surface waves (SHSW) in semi-infinite elastic media with vertically periodic continuous and/or discrete variation of material properties. The existence and spectral properties of the SHSW are shown to be intimately related to the shape of the properties variation profile. Generally, the SHSW dispersion branches represent randomly broken spectral intervals on the ( ω , k ) plane. They may, however, display a particular regularity in being confined to certain distinct ranges of slowness s = ω / k , which can be predicted and estimated directly from the profile shape. The SHSW spectral regularity is especially prominent when the material properties at the opposite edge points of a period are different. In particular, a unit cell can be arranged so that the SHSW exists within a single slowness window, narrow in the measure of material contrast between the edges, and does not exist elsewhere or vice versa. Explicit analysis in the ( ω , k ) domain is complemented and verified through the numerical simulation of the SH wave field in the time–space domain. The results also apply to a longitudinally periodic semi-infinite strip with a homogeneous boundary condition at the faces.

Shear Horizontal Surface Waves in a Piezoelectric-Piezomagnetic coupled layered half-space

Article Shear Horizontal Surface Waves in a Piezoelectric-Piezomagnetic coupled layered half-space was published on June 1, 2009 in the journal International Journal of Nonlinear Sciences and Numerical Simulation (volume 10, issue 6).

A shear horizontal surface acoustic wave sensor for the detection of antigen–antibody reactions for medical diagnosis

Abstract In this paper we describe the development of a shear horizontal surface acoustic wave immunosensor for medical diagnostics. There exists a strong interest in the rapid detection of antigen–antibody reactions at small concentrations in the μ g/ml region in plasma, serum, or whole blood. Sensors whose operating principle is based on shear horizontal acoustic surface waves are well suited for this. We have used a spin-on glass film for the guidance of the surface wave as well as for the protection of the aluminum structures of the surface wave transducers from aggressive analyte liquids. This film has proven to considerably enhance the sensitivity of the device, and to simultaneously provide a durable protection of the transducers. Furthermore, polymers based on polyvinylamines have been used for the first time for immobilization of the capture protein. This technique effectively prevents the undesired binding of foreign substances like cells, non-specific antibodies, or other proteins at the sensor surface.

Shear horizontal BG surface acoustic waves on piezoelectrics: a historical note

In December of 1968 Jeffrey Bleustein of Yale University published an article predicting the existence of a new type of transverse surface acoustic wave (SAW) that could propagate on the surface of a piezoelectric crystal. This was followed within 20 days by the publication of an article by Yuri Gulyaev in January of 1969 predicting the same basic surface wave propagation. The wave took on the name Bleustein-Gulyaev or BG-wave, joining the names of Rayleigh, Love, Sezawa, and Stonely for distinct types of SAW. But is there more to the story than this? Were there works preceding those of Bleustein and Gulyaev which signaled an interest in exploring a new surface wave mode on piezoelectrics? What about the work of Shimizu, Nakamura, and Ohta, who in April of 1969 published both theoretical and experimental verification of the existence of such a wave independent of the knowledge of the Bleustein and Gulyaev papers? This paper explores the early roots and characteristics of the shear horizontal surface wave on a piezoelectric.

Non-dispersive and dispersive electromagnetoacoustic SH surface modes in piezoelectric media

This paper deals with a detailed analysis of the electromagnetic problem for the propagation of shear horizontal (SH) surface waves in a non-conducting piezoelectric half-space. The compatibility equations are solved in both cases of grounded surfaces and surfaces matched with an external potential. It is shown that a unique quasi-acoustical mode exists in non-dispersive media and the corresponding solution is worked out in a closed form having recourse to a method of complex analysis. Dispersive half-spaces are considered accounting for a one-resonance model and the dispersion equation is numerically solved for a matched surface. Two types of admissible surface waves are found in different frequency ranges. One mode generalises the well-known Bleustein–Gulyaev wave, while the second one is a quasi-electromagnetic mode occurring above the characteristic frequency of the model. Results are compared with those obtained by the quasi-static approximation.

Generally polarized acoustic waves trapped by high aspect ratio electrode gratings at the surface of a piezoelectric material

It has been shown theoretically and demonstrated experimentally that shear horizontal (SH) surface waves can exist when the surface of an isotropic substrate is perturbed by a strong corrugation, for instance consisting of deep grooves etched in the substrate, whereas these waves cannot exist without this perturbation. It is shown in this article that a periodic array of metallic electrodes (wires) exhibiting large aspect ratios deposited over a piezoelectric substrate give rise to surface acoustic waves with general polarization. The admittance of an interdigitated transducer, which is a basic tool for predicting the waves parameters, is calculated by a combination of finite element analysis and a boundary integral method. This approach has been extended to obtain the polarization of the acoustic waves. For different piezoelectric substrates, we predict various surface acoustic modes and their polarization. Along with mostly SH modes, we also find modes mostly polarized in the sagittal plane. We discuss the frequency behavior of the surface modes as a function of the electrode height compared to the period.

A solution for transient surface waves of the B-G type in a dissipative piezoelectric crystal

We derive a solution to the problem of shear horizontal electroacoustic surface waves in a piezoelectric half-space. We formulate a time-domain dynamic problem accounting for time dispersion for both electric and elastic fields and use a separation of variables to express the solution in terms of a wave propagator. Transient surface waves of the B-G type are found to propagate with a constant speed and exponentially decay in space. Their amplitude vanishes at large distances from the boundary as the reciprocal of the depth. Dispersive and non dispersive solutions are compared.

Specral magnitudes and seismograms measure radiation from seismic sources

For over 100 years, efforts have been made to measure the strength of earthquakes. In 1935, Richter established the local magnitude scale, ML, for earthquakes in Southern California using Wood Anderson Seismographs. The seismic waves used had periods ranging from 0.1 s to 2 s. In 1945, Gutenberg [1945a] developed the surface wave magnitude scale (Ms) based on the amplitudes of horizontal surface waves with periods of (20±3) s, recorded at large distances. Gutenberg [1945b] also used seismic body P and S waves, with average periods of 5 s and 10 s, respectively, to introduce the bodywave magnitude scale (mb).

The electromagneto-acoustic surface wave in a piezoelectric medium: The Bleustein–Gulyaev mode

By discarding the quasi-static approximation, this paper gives the exact solutions of a shear horizontal electromagneto-acoustic surface wave mode in a class of piezoelectric media. As the wave speed is much less than the speed of light, the solution degenerates to the well-known Bleustein–Gulyaev wave, or Maerfeld–Tournois wave. Taking into account both optical effect as well as the contribution from the rotational part of electric field, the solutions obtained here are not only valid for any wave speed range, but also provide accurate formulas to evaluate the acousto-optic interaction due to the piezoelectricity.

Analysis and experimental study of surface transverse wave resonators on quartz

Since surface transverse wave resonators are becoming increasingly used in high-frequency electrical component applications, there is a pressing need for reliable simulation tools in this field. We develop analytical techniques for prediction of the resonant peaks of practical devices and apply them to the results of experiments in this laboratory and in others. The devices investigated are three-grating structures composed of three arrays of metal strips or grooves on quartz substrates, which support a shear horizontal surface wave polarization. The outer gratings act as mirrors for the cavity resonance. The influence of the main design parameters on the resonator response is studied.

Acoustoionic interaction of SH surface waves with dilute ionic solutions

A theory describing the acoustoionic interaction of shear horizontal (SH) surface waves with viscous conductive ionic liquid is presented. A Green's function formulation that accounts for the acoustoelectric interaction with ions and dipoles in the solution is obtained for the surface potential in terms of the liquid and piezoelectric crystal parameters. For dilute ionic solutions, simple closed-form expressions for the velocity change and attenuation are obtained in terms of liquid conductivity and dielectric constant and the piezoelectric coupling coefficient. It is shown that SH surface waves in particular and acoustic waves in general can be used to perform microanalysis of dilute ionic solutions, detecting conductivity, dielectric constant, and relaxation frequency. The analysis, which was done for a simple crystal class, the hexagonal (6 mm), shows results which compare very well with exact numerical computations.

Van der Waals coupled surface waves in nonpiezoelectric crystals and thin films

The coupling due to the van der Waals and the dissipative thermal interactions of surface waves propagating along a thin vacuum gap between nonpiezoelectric crystals is investigated. The propagation of the Rayleigh and the shear horizontal surface waves in coupled massive crystals and the slow bending waves in coupled thin films is considered. It is shown that the van der Waals attractive forces cause a negative shift of the velocity and the existence of a terminal point k 0 for the propagation of the long-wavelength Rayleigh and bending waves, in which the frequency of the coupled waves goes to zero. The anomalous absorption of the grazing bulk shear acoustic waves scattered from the gap is predicted.

Nonlinear surface modes in crystals

We examine theoretically the influence of nonlinearity on characteristics of the shear horizontal surface waves in crystals. We demonstrate that the dynamics of the system may be described in the framework of an effective nonlinear parabolic equation, the so-called nonlinear Schrödinger equation. We predict the existence of a set of nonlinear surface modes; the simplest mode is described by a sech-type function of z, z being the distance from the surface. The higher order modes have internal frequencies stimulated by the nonlinearity. All these modes decay in the crystal as u 0 exp( −z z 0 ), z ⪢ z 0~ u 0 −1 where u 0 is the wave amplitude at the surface. The creation of the modes from an arbitrary surface excitation has a threshold.

Velocity of shear horizontal surface waves on an isotropic elastic cylinder with finite width

Theoretical and experimental results describing the propagation of shear horizontal (SH) surface waves on an isotropic elastic cylinder are presented. Analytical formulas for group velocities are developed. The velocity of impulses of the SH surface waves is determined experimentally. Subsequently, the experimental results are compared to the theoretical values. The measured velocity is close to the group velocity calculated according to our theory for cylinders of finite width. As yet, the existing theories consider only the propagtion of SH surface waves over the unlimited cylinders [I. A. Viktorov, Sov. Phys. Acoust. 20, 199 (1974) and L. M. Brekhovski, Sov. Phys. Acoust. 13, 541 (1967)].

Shear horizontal surface waves on piezoelectric ceramic with layered structure

This paper presents theoretical and experimental results describing the propagation of SH (shear, horizontal) surface waves on a piezoelectric ceramic with a surface layer of different polarization than that in the substrate. An analytical formula for the group velocity of the SH surface waves is developed. The velocity of impulses of the SH surface waves is determined experimentally. Further, the theoretical results are compared to the experimental values.

Effects of liquid relaxation time on S H surface waves liquid sensors

Effects of liquid relaxation time on the propagation characteristics of shear horizontal (SH) surface waves at the interface between a piezoelectric crystal and a fluid medium are theoretically analyzed for liquid sensor applications. General closed-form expressions are derived for both velocity change and attenuation coefficient for a Maxwellian viscoelastic fluid that can be treated as a Newtonian fluid or as an amorphous solid, depending on the liquid shear relaxation time. It is shown that relaxation time becomes important as the liquid viscosity and/or the wave frequency increases. The result is a saturation level in the propagation loss and the device sensor frequency shift as the liquid relaxation time approaches the wave period. The effect of liquid relaxation is thus to set detection limits on the range of liquid vicosity that can be measured. However, it is also shown that in actual sensor applications, a trade-off can be performed between the maximum measurable viscosity and the SH surface wave device frequency of operation, and thus the device sensitivity.