Search

Present study primarily focuses on interpreting the propagation pattern of Shear horizontal (SH) wave in a piezo-composite layered cylinder. The structure consists of three concentric cylinders com...

The electromagnetic acoustic transducer (EMAT) is widely used in In-Line Inspection of gas pipeline. However, the transduction efficiency of the EMAT transmitter is lower compared with the traditional piezoelectric transducer and needs improving. To enhance the amplitude of the received signal, an improved periodic-permanent-magnet EMAT is provided as well as its construction method to generate shear horizontal guided waves propagating in the circumferential direction. By designing a racetrack coil and magnetic array with the same radian of the annular pipeline, the EMAT is more suitable to generate the circumferential wave in the pipeline. The performance of the EMAT transmitter has been assessed with the validated finite element model.

In this work, the scalability between frequency and electromechanical coupling factor ( $k_{t}^{2}$ ) is demonstrated by shear horizontal surface acoustic wave (SH-SAW) resonators based on lithium niobate on insulator (LNOI). The dispersive characteristic is observed from the simulation, and is later substantiated by the fabricated devices with various wavelengths. A high electromechanical coupling factor ( $k_{t}^{2}$ ) of 25.1% was recorded throughout the measurement at a normalized LN thickness of 0.25. Linear response was also disclosed under different input power, verifying the adoption of LNOI topology. Thus, the measured results unveil the potential usage of SH-SAW resonators for wideband applications in communication systems.

The propagation of shear horizontal (SH) surface waves in piezoelectric semi-infinite bodies is investigated theoretically. The surface stress exerting on the boundary is taken into account through...

In this work, the shear horizontal (SH) wave dispersion in two dissimilar nanolayers is investigated by using the surface elasticity theory in which the surface effects are featured by surface elastic constants. It is found that the SH wave dispersion shows distinct dependence on the nanolayer thickness as well as the surface elastic constants. The larger the surface elastic modulus and/or the smaller the thickness, the higher the phase velocity. In particular, as the wave frequency approaches zero, the analytical relation between the phase velocity in the first mode dispersion and the surface elastic constants is deduced. Thereby, a facile method is suggested to determine the surface elastic constants from the phase velocity of SH waves scattered in nanolayers.

It this study, omni-directional shear-horizontal wave transduction is performed using a specially configured magnetostrictive patch transducer in a ferromagnetic plate. For a ferromagnetic plate, unavoidable magnetic flux leakage into the plate not only results in poor transduction efficiency but also generates unwanted waves within the plate. These problems must be overcome to inspect ferromagnetic plates using the transducer. Therefore, we investigate the reasons for the poor performance and propose a method to improve its performance. The effectiveness of the proposed method was validated through simulations and experiments.

The fundamental shear horizontal (SH) wave in thin-walled structures shows appealing features for structural health monitoring (SHM) applications. Its efficient generation and reception however remain a critical and challenging issue. Magnetostrictive transducers (MsTs) show proven ability in exciting strong SH waves due to the high piezomagnetic coefficient of the ferromagnetic foil. In this study, to investigate the fundamental SH wave generation using MsTs and their design, a theoretical model is established based on the shear-lag model and the normal mode expansion method. The coupling of an MsT with a host plate is achieved by a bonding layer, whose mechanical property is modelled through the continuous shear stress across the thickness. The theoretical model is validated using finite element simulations in terms of generation mechanism and some typical features associated with the fundamental SH wave component. Meanwhile, wave field is visualized using a 3D Laser scanning vibrometer system. Experimental results within a wide frequency range show a good agreement with the theoretically predicted results. Influences of the coil configuration and bonding conditions are further investigated using the proposed model. The study offers guidelines to system design and optimization for fundamental SH wave generation in views of guided-wave-based SHM applications.

This study aims to develop a shear horizontal guided wave based technique to evaluate the interfacial adhesion of aluminium-epoxy-aluminium tri-layer in a lap shear joint. A 3-D Multi-physics finite element model was developed to investigate the physics of the interaction of SH modes with a tri-layer structure. By employing the boundary stiffness approach, different cases of interfacial adhesion-ranging from perfect bond, intermediate and weak bond, were simulated. Frequency-wavenumber analysis reveals that at the bond overlap region, the incident SH0 wave mode-converts to fundamental (SH0-like) and first-order(SH1-like) modes. The dispersion characteristics of first-order mode (SH1-like) was found to be dependent on the adhesion level, and this influences the time responses collected on a receiver plate in guided wave through-transmission configuration. Experiments were carried out on aluminium-epoxy-aluminium lap shear joints using PPM-EMAT transducers. The analysis shows that this technique can detect and quantify different levels of adhesion, rather than merely classifying as good or bad bonds.

The authors have recently reported on the attractive properties of shear-horizontal type feature guided (SHB) waves for the inspection of 90� plate bends. Further to this, here the interaction of the SHB mode with transverse and longitudinal defects in the bend region is studied using 3D finite element simulations validated by experiments. Trends are discussed in light of the underlying wave mechanics principles. The results show that the SHB mode yields improved through-thickness defect resolution capabilities as compared to regular plate guided SH waves in view of mode confinement and higher frequencies used. � 2015 Elsevier Ltd. Allrightsreserved.

In this work, a guided shear horizontal mode surface acoustic wave (SH-SAW) sensor, fabricated by patterning gold (Au) interdigitated electrodes (IDE) on a 64° YX-LiNbO3 based piezoelectric substrate, was used for the detection of heavy metal compounds. A flow cell, with a reservoir volume of 3 μL, which employs inlet and outlet valves for the microfluidic chamber and polydimethylsiloxane (PDMS) based microfluidic channels, was also designed and fabricated using an acrylic material. The frequency based response of the SAW sensor toward varying concentrations of heavy metal compounds such as lead nitrate (PbNO3) and cadmium nitrate (CdNO3) were investigated. As the surface acoustic wave propagates on the substrate, between input and output IDEs, a shift in the resonant frequency of the SAW device was observed due to the change in velocity of the wave caused by the varying concentrations of the test analytes. The results obtained demonstrated the capability of the system to detect picomolar level concentrations. The response of the SAW sensor is analyzed and presented in this paper.

The propagation characteristics of surface acoustic waves (SAWs) on Y-cut X propagating Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PIN-PMN-xPT) substrates with different PT composition (x=0.28 and 0.32) were theoretically analyzed. The calculated results indicated existence of a shear horizontal (SH) SAW with ultrahigh electromechanical coupling factor K2. The variation of SAWs properties with rotated Euler angle θ was also investigated. The largest K2 for the SH SAW could reach 60% when θ=45°. The K2 for the SH SAW with different PT contents was calculated, and it was found that the K2 for the 0.32PT substrate was larger than that for 0.28PT substrate. The influence of Mn-doping on SAW properties for YX-PIN-PMN-0.28PT substrate was also analyzed. The simulated results showed that after Mn-doping the velocity increased while the K2 decreased, which confirmed the phenomenon of “hard” effect caused by Mn-doping.

We have investigated thermal effect on band gaps of shear horizontal (SH) waves propagating through a layered metallic periodic structure. For a metallic material, the lattice length varies slightly with temperature while the Young's modulus is strongly thermosensitive. Firstly, the dispersive equation without thermal effect was derived by the transfer matrix method. Secondly, the thermal effect on the material coefficients was investigated. Finally, the dispersive curves at different temperatures with changing incident angles were drawn. It reveals that the band gaps get a greater impact in high-frequency regions than those in low-frequency regions. The results can provide theoretical basis for the production of phononic crystals.

This paper aims at the theoretical analysis of the propagation of shear horizontal waves in an ultra-thin plate-like film with nano-scale thickness via the surface elasticity theory. Both the surface and the bulk of the material are assumed to be isotropic and linearly elastic. The governing equations with non-classical boundary conditions are derived. Numerical calculations are performed for the first few symmetric and antisymmetric modes of shear horizontal waves. It is found that the surface effects become significant with the decrease of the film thickness. In contrast to the classical case, all the modes in the thin film at nano-scale are dispersive. A special symmetric mode appears and stays close to the descending first antisymmetric mode. They may escape and stop propagating above certain frequencies.

We study the propagation of shear horizontal waves between the interface of two piezoelectric materials with an electro-mechanical imperfect contact. Mechanical and electrical imperfections are modeled by means of a spring and a capacitor, respectively. The corresponding mathematical expressions for the imperfect contact are given in this article. The system of differential equations for the waves in the considered half-space is derived and the associate solutions are found. A general expression for the dispersion relation, not reported previously in the literature, is given in an explicit form, with the diverse limit cases analyzed in detail. In some of these limit cases, new expressions are also obtained, which predict the existence of interfacial waves. In the other cases, where already reported results exist, a comparison with them is done. Some physical interpretations are derived from the limit cases. The influence of mechanical and electrical imperfect contacts are shown in some numerical examples.

The prototype implementation of a permanently installable high temperature crack monitoring system is described. The system uses an array of waveguides to excite shear horizontal (SH) waves on the surface of the component that is to be inspected. The waveguide is made of poorly heat conducting stainless steel so that it can sustain a large temperature gradient. This ensures that conventional piezoelectric transducers can be used at one end of the waveguide to excite ultrasonic waves while the other end is in contact with the component to be monitored which is situated in a harsh environment at elevated temperature (up to 600 °C). Different crack monitoring strategies using SH waves are discussed. Simulation and experimental results for the array prototype on notched plates are presented. Furthermore, experimental results on samples containing fatigue cracks are shown and measurement results that were collected from a notched plate in a furnace at 550 °C are also presented.

We analyze the propagation of shear horizontal (SH) piezoelectric waves guided by a plate of polarized piezoceramics between two piezoceramic half-spaces with imperfectly bonded interfaces. The interfaces are described by the so-called shear-lag model with an elastic constant characterizing the interface physical behavior. Exact dispersion relations are obtained. It is found that the waves are sensitive to the physical nature of the interfaces. The results are useful for acoustic wave devices.

The Propagation characteristics of a shear horizontal (SH) wave in a trilayer structure having a viscous fluid layer is analyzed from a numerical analysis. Acoustic phase changes under application of electric fields in a nematic liquid crystal cell are measured using the SH wave. The acoustic phase advances with increasing the applied electric field. This result corresponds with the viscosity change based on a molecular reorientation of the liquid crystal. In dynamic response measurement, the response times in the phase and the optical measurements are different, because the measured area of the acoustic phase is only the vicinity of the glass surface.

The acoustic phase of a shear horizontal (SH) wave propagating into a nematic liquid crystal cell is measured. To investigate the acoustic phase depending on the director angle of a liquid crystal, the two SH wave devices having different initial molecular orientations are fabricated. The acoustic phase change of the SH wave devices is measured for various applied electric fields. The numerical analyses are also performed by considering director distribution in the nematic liquid crystal layer. The experimental acoustic phase changes are well accorded with the calculated shear stresses as a viscous resistance.

The interference of humidity on an ammonia sensor was studied in this work. The shear horizontal surface acoustic wave (SH-SAW) device coated with l -glutamic acid hydrochloride was fabricated and used as an ammonia sensor. The sensitivity of the SH-SAW ammonia sensor was 4.6 ppm/ppm and the mass loading dominated the perturbation in dry air at 50 °C. As the humidity rose in the environment, the perturbation was primarily from the elastic effect. This work estimated the cross-sensitivity of the interference of humidity. Finally, the neural network technique was used to identify ammonia in the environment.

Circumferential shear horizontal (SH) waves are used for the inspection and sizing of axial cracks in pipelines. Experiments on two sample pipes having notches with different depths and lengths were carried out utilizing magnetostrictive sensor (MsS) technology for generating circumferential shear horizontal guided waves. A simplified two-dimensional model for crack sizing in pipes was studied through wave-reflection amplitude coefficients. The wave-reflection amplitudes are affected by both defect depths and lengths. To estimate the defect depth, which is critical, length compensation was taken for defects shorter than the beam width. An axial scan was carried out for the defect length estimations and the length compensation. Based on this axial scan, an approximate two-dimensional theory has been developed that has improved the defect depth estimation greatly. Two-dimensional boundary element modeling analysis and normal mode expansion technology are used to study defect sizing theoretically in a pipe-l...

In this work a modal analysis was employed to study generation of the second harmonics of shear horizontal (SH) modes in a solid plate. Under second order perturbation, second-harmonic generation will occur accompanying SH mode propagation due to the bulk elastic non-linearity of plate material. In solid plate the total second-harmonic fields of a SH mode propagation are regarded as sum of the fields of a series of double frequency Lamb modes (DFLMs). The contribution of each DFLM component to the total second-harmonic fields is dependent of the difference of phase velocities of the corresponding DFLM and SH mode. The analysis results show that the DFLM field component may have cumulative growth effect once its phase velocity exactly or approximately equals that of a SH mode. It is also found that the fields of the total second harmonics of a SH mode are only symmetrical. The examples of field distributions of several DFLMs on the plate surface are considered.

Shear horizontal waves, in the form of transient perturbations, are considered at the interface between two different viscoelastic solids. The admissibility of these interfacial waves is studied via the asymptotic expansion of the Laplace transform of the viscoelastic kernel. The compatibility condition is reduced to a set of algebraic systems which can be solved iteratively to the desired order in the asymptotic expansion. Two classes of solutions are found which correspond to transient waves decaying away from the interface and attenuated along the propagation direction. Numerical examples are given to illustrate the results.

In this paper, we realize the topological edge modes of a shear horizontal (SH) guided wave in the one-dimensional (1D) composite structure that exist at the phononic band gaps opened at the center of the Brillouin zone (BZ), or at the zone boundary, or both. Furthermore, we investigate the topological edge modes in periodic acoustic systems result from both Bragg scattering and local resonances. In particular, we find and demonstrate that, in our system where topological and trivial defect states coexist, these results provide a new paradigm for manipulating the existence of the interface states in a set of prescribed band gaps that can have potential applications in the design of novel acoustic devices.

We developed a Green’s function formalism to investigate the localized and resonant acoustic modes of shear horizontal polarization associated with the surface of a substrate supporting a periodic array of wires. Each material is assumed to be an isotropic elastic medium. The calculation can be applied to an arbitrary choice of the shape and elastic parameters of the wires. The surface modes are obtained as well-defined peaks of the densities of states (DOS). In this paper, we calculate the dispersion curves of the surface modes for wires of parabolic section, and discuss their behaviour as a function of the elastic parameters, the height and the periodicity of the wires.

We study the shear horizontal and sagittal elastic waves in polytype superlattices, formed by the periodic repetition of three different constituent materials. We use the surface Green function matching method for N non-equivalent interfaces in order to obtain the dispersion relations and the density of states. In this way it is possible to obtain the spatial localization of the different modes. The influence of the variation of the thickness of the constituent materials on the dispersion relation of the elastic modes is studied.

Acoustic wave devices are often used as chemical sensors. Those described in the literature are merely based on bulk waves or on surface waves (SAW), also called Rayleigh waves. In this paper we describe another type of device, based on shear-horizontal acoustic plate mode (SH-APM) waves. Experimental results with various modes concerning the influence of the temperature, the viscosity and the concentration of NaCl and tris(hydroxymethyl)aminomethane (Tris) in aqueous solution are presented: they show the better sensitivity of higher-order modes. These results show that this device can be used as a sensor in a biological medium.

Inclined incidence of a shear horizontal elastic wave on a periodic structure of piezoelectric layers with metallized interfaces is considered. The layers are supposed to be made from the identical crystal of hexagonal symmetry but have alternating widths d1,d2. Due to the condition of fixed electropotential, each interface provides the reflection proportional to the parameter of electromechanical coupling q2. The interference of the reflected waves in the periodic structure causes the existence of the Bragg resonances in the reflection‐transmission spectrum so that ‖R‖max≊1 for a sufficiently large number of layers. Since q2≪1, the considered reflection spectrum exhibits some specific features such as high selectivity, modulation of the heights of the Bragg maximums depending on the value d1/(d1+d2), and the extinction effect.

Theoretical description of Brillouin scattering from shear horizontal (SH) acoustic surface phonons in a generic multilayer structure with arbitrarily smooth interfaces is given. To evaluate the p-s Brillouin cross-section, the SH phonon spectrum, the transmitted zeroth-order field and the fluctuating polarization vector radiating the Brillouin light are computed numerically by means of a method that can take into account any depth profiles of elastic, elasto-optic and dielectric properties of the medium including electromagnetic absorption. As an application the case of a silicon on insulator structure with both sharp and diffuse interfaces is illustrated.

A shear horizontal mode surface acoustic wave (SH-SAW) device has many attractions for chemical-sensing applications in liquid media. The SH-SAW that propagates on 36° rotated Y-cute, X-propagating LiTaO3 is affected by a strong acoustoelectric interaction between the piezoelectric potential and electric properties of the adjacent liquid. This paper describes an enzyme-immobilized SH-SAW biosensor in which the detection principle is the acoustoelectric interaction due to the pH change in the enzyme reaction. Two kinds of enzymes, urease and cholinesterase, are immobilized on the sensor surface and highly sensitive detection of the enzyme reaction is obtained experimentally. The urease-immobilized SH-SAW biosensor is implemented in a liquid-flow system. By using the cholinesterase-immobilized SH-SAW sensor, we have succeeded in detecting an inhibition effect of a pesticide.

We present a novel, smart sensing system developed for the flavour analysis of liquids. The system comprises both a so-called “electronic tongue” based on shear horizontal surface acoustic wave (SH-SAW) sensors analysing the liquid phase and a so-called “electronic nose” based on chemFET sensors analysing the gaseous phase. Flavour is generally understood to be the overall experience from the combination of oral and nasal stimulation and is principally derived from a combination of the human senses of taste (gustation) and smell (olfaction). Thus, by combining two types of microsensors, an artificial flavour sensing system has been developed. Initial tests conducted with different liquid samples, i.e. water, orange juice and milk (of different fat content), resulted in 100% discrimination using principal components analysis; although it was found that there was little contribution from the electronic nose. Therefore further flavour experiments were designed to demonstrate the potential of the combined electronic nose/tongue flavour system. Consequently, experiments were conducted on low vapour pressure taste-biased solutions and high vapour pressure, smell-biased solutions. Only the combined flavour analysis system could achieve 100% discrimination between all the different liquids. We believe that this is the first report of a SAW-based analysis system that determines flavour through the combination of both liquid and headspace analysis.

Oblique incidence of a shear horizontal elastic wave on a periodic structure of identical piezomagnetic layers, separated by thin superconductive coatings, is considered. The Bragg resonance of reflection arising due to the s state on the interfaces is analyzed. It is shown that for a sufficiently large number of layers the reflection coefficient R may change from zero to R ≈1 for the n-s transition.

A Love plate device, based on an SSBW piezoelectric substrate coated with a polymer (PMMA) layer, was used to excite a surface guiding shear horizontal wave. The surface mass sensitivity of the device was calculated as a function of the thickness of the polymer layer, usin a modelling theory derived for the polymer-Love plate. LB films were used to assess experimentally the surface mass sensitivity and results were compared with theoretical predictions. Investigation of protein interaction with the PMMA surface was performed by following the adsorption of IgG in the range 1–400 μg/ml. Finally, the deposition of a protein multilayer, consisted of IgG/anti-IgG and protein A, was clearly detected using the polymer-coated Love plate device.

We investigate the effective viscosity of a nematic-liquid-crystal (NLC) for viscosity measurement using a shear horizontal (SH) wave propagating through a glass substrate loaded with the NLC. The phase measurement of the SH wave determines the NLC viscosity because SH wave propagation depends on loaded material viscosity. Using this viscosity measurement, we can also determine the viscosity anisotropy of the NLC with director reorientation. In experiment, phase shifts are detected when voltages are applied to a NLC layer. The measured phases show an unpredictable shift which cannot be explained by conventional director angular dependence of viscosity. To analyze the phase shifts quantitatively, we introduce average effective viscosity for the viscosity measurement using SH wave. This effective viscosity is calculated considering the NLC director configuration and SH wave penetration into the NLC layer. The phase shifts calculated from the effective viscosity well agree with the measured phase shifts. The use of effective viscosity enables quantitative analysis for NLC viscosity measurement using the SH wave and also clarifies the mechanism of the unpredictable SH wave phase shift with director reorientation.

Inelastic electron scattering measurements and lattice dynamical analysis of the vibrational properties of Ag(110) surfaces are presented. The measurements include detection of odd-symmetry shear horizontal modes throughout the two-dimensional Brillouin zone, and the lattice dynamical analysis explores the effects on surface interaction models arising from the requirement that shear mode properties are correctly accounted for by the model. This new constraint leads to a lattice dynamical model which is significantly different from models which are deduced on the basis of only evensymmetry surface vibrational modes.

The propagation characteristics, mainly the propagation loss and the bulk wave radiation loss of a pure shear-horizontal-type surface acoustic wave on (0/spl deg/, 0, 90/spl deg/)-cut langasite with a high-density thin film such as a gold (Au) film or a tantalum pentoxide (Ta/sub 2/O/sub 5/) dielectric film, are investigated experimentally. The cut angles /spl theta/ of 0/spl deg/, 10/spl deg/ and 20/spl deg/ were chosen because the coupling factor of 1.0% and a zero temperature coefficient of delay (TCD) can both be expected around these cut angles. The experimental results showed that the propagation characteristics, that is the energy-trapping effects of loading with the with the Ta/sub 2/O/sub 5/ film, depend on the cut angle. For the Au film, the propagation loss and the bulk wave radiation loss showed relatively small values at /spl theta/=10.

A shear horizontal surface acoustic were (SAW) that propagates on 36° rot. Y-cut X-propagating LiTaO3 immersed in a liquid is affected by an acoustoelectric interaction between the piezoelectric potential and the electrical properties of the materials in the liquid. Using the SAW device, pH changes in enzymatic reactions can be detected by the measurement of the SAW velocity change caused by a pH change associated with the reactions. In this paper, preliminary experiments on a urea—urease reaction and the inhibition effect of the butyrylcholine chloride-cholinesterase reaction due to a pesticide are reported.

Using the mathematical software MapleV, a model was previously developed to determine the mass sensitivity of Shear Horizontal Acoustic Plate Mode (SH-APM) sensors. The theoretical approach and results obtained are briefly recalled in this paper. They led to the realization of test devices. To validate the model in the case of a mass loading effect, SH-APM devices were tested in gas medium and allowed the detection of organophosphorous vapors.

One-port surface acoustic wave resonators (SAW) were fabricated and characterized using Y-cut X propagating relaxor based ferroelectric single crystals of Pb(Mg1/3Nb2/3)O3-33%PbTiO3 and Pb(In1/3Nb2/3)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT). The experimental results demonstrated ultrahigh electromechanical coupling factor K2 of ∼60% for shear horizontal SAW and a relatively strong spurious resonance due to the Rayleigh-type SAW which can be sufficiently suppressed with Au electrode of large thickness. Characteristics of temperature stability, sensitivity to DC bias voltage, and homogeneity for the two resonators were evaluated and compared. The results showed similar instability of domain structure, and PIN-PMN-PT resonators have better temperature stability, but inferior homogeneity compared to that of PMN-33%PT resonators.

High-resolution He atom inelastic-scattering experiments provide evidence for the shear horizontal surface phonons on the {ital in} {ital situ} cleaved NaCl(001) surface. The measurements were made in a sagittal plane along the [210] azimuth and beyond the first surface Brillouin zone. A slab calculation using the breathing shell model and a surface perturbation that fulfills invariance conditions is used to identify the polarizations of the observed surface phonons. {copyright} {ital 1996 The American Physical Society.}

Experimental evidence and a theoretical explanation of Brillouin scattering from shear horizontal surface acoustic phonons in an Si buffer with a buried SiO2 layer are given in both the discrete and continuum parts of the spectrum. This is the first experimental observation of Brillouin scattering from sheer horizontal acoustic phonons in the continuum spectral region. The intensity and position of peaks in Brillouin spectra have been qualitatively described in terms of the layer projected phonon density of states calculated for such a structure.

We present an exact numerical method for obtaining the variation in the density of states associated with the adsorption of wires on a flat surface and with channels cut into an otherwise planar surface. This general method is presented for the determination of the resonances of shear horizontal polarization associated with such surface protuberances or indentations.

The dispersion curve of the shear horizontal surface phonon along \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} X\ifmmode\bar\else\textasciimacron\fi{} ([1\ifmmode\bar\else\textasciimacron\fi{}10]) on Ni(110) has been measured with use of high-resolution electron-energy-loss spectroscopy. The frequency of this phonon at X\ifmmode\bar\else\textasciimacron\fi{} is found to be 169 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Theoretical calculations provide an excellent account of the loss spectra measured in scattering geometries where excitation of shear horizontal modes is forbidden, and those in which they contribute strongly. The frequency of the shear horizontal phonon at Y\ifmmode\bar\else\textasciimacron\fi{} is measured also, and found to be approximately 116 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. A model introduced earlier for Ni(110) is in reasonable accord with the data, though a full account requires the introduction of noncentral forces into the lattice dynamics.

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.