Morched Ben Amor

Love waves propagation in a transversely isotropic piezoelectric layer on a piezomagnetic half-space

A theoretical approach is taken into consideration to investigate Love wave propagation in a transversely isotropic piezoelectric layer on a piezomagnetic half-space. The magneto-electrically open and short conditions are applied to solve the problem. The phase and group velocity of the Love wave is numerically calculated for the magneto-electrically open and short cases, respectively. The variations of magneto-electromechanical coupling factor, mechanical displacements, electric and magnetic potentials along the thickness direction of the layers are obtained and discussed. The numerical results clearly show the influence of different stacking sequences on dispersion curves and on magneto-electromechanical coupling factor. This work may be relevant to analysis and design of various acoustic surface wave devices constructed from piezoelectric and piezomagnetic materials.

Effect of a functionally graded soft middle layer on Love waves propagating in layered piezoelectric systems

Numerical examples for wave propagation in a three-layer structure have been investigated for both electrically open and shorted cases. The first order differential equations are solved by both methods ODE and Stiffness matrix. The solutions are used to study the effects of thickness and gradient coefficient of soft middle layer on the phase velocity and on the electromechanical coupling factor. We demonstrate that the electromechanical coupling factor is substantially increased when the equivalent thickness is in the order of the wavelength. The effects of gradient coefficients are plotted for the first mode when electrical and mechanical gradient variations are applied separately and altogether. The obtained deviations in comparison with the ungraded homogenous film are plotted with respect to the dimensionless wavenumber. The impact related to the gradient coefficient of the soft middle layer, on the mechanical displacement and the Poynting vector, is carried out. The numericals results are illustrated by a set of appropriate curves related to various profiles. The obtained results set guidelines not only for the design of high-performance surface acoustic wave (SAW) devices, but also for the measurement of material properties in a functionally graded piezoelectric layered system using Love waves.

Lamb waves propagation in layered piezoelectric/piezomagnetic plates

HighlightsThe first order differential equation and stiffness matrix method are developed.The phase velocity of the Lamb wave is calculated for the magneto‐electrically open and short cases.The influence of stacking sequences and thickness ratio on dispersion curves and on magneto electro‐mechanical coupling factor. Abstract A dynamic solution is presented for the propagation of harmonic waves in magneto‐electro‐elastic plates composed of piezoelectric BaTiO3(B) and magnetostrictive CoFe2O4(F) material. The state‐vector approach is employed to derive the propagator matrix which connects the field variables at the upper interface to those at the lower interface of each layer. The ordinary differential approach is employed to determine the wave propagating characteristics in the plate by imposing the traction‐free boundary condition on the top and bottom surfaces of the layered plate. The dispersion curves of the piezoelectric–piezomagnetic plate are shown for different thickness ratios. The numerical results show clearly the influence of different stacking sequences as well as thickness ratio on dispersion curves and on magneto‐electromechanical coupling factor. These findings could be relevant to the analysis and design of high‐performance surface acoustic wave (SAW) devices constructed from piezoelectric and piezomagnetic materials.

Lamb waves propagation in functionally graded piezoelectric materials by Peano-series method.

The Peano-series expansion is used to investigate the propagation of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb wave modes in a functionally graded piezoelectric material (FGPM) plate. Aluminum nitride has been retained for illustration, it is polarized along the thickness axis, and at the same time the material properties change gradually perpendicularly to the plate with an exponential variation. The effects of the gradient variation on the phase velocity and the coupling electromechanical factor are obtained. Appropriate curves are given to reflect their behavior with respect to frequency. The highest value of the electromechanical coupling factor has been observed for S0 mode, it is close to six percent, conversely for A0 mode it does not exceed 1.5%. The coupling factor maxima undergo a shift toward the high frequency area when the corresponding gradient coefficient increases. The Peano-series method computed under Matlab software, gives rapid convergence and accurate phase velocity when analysing Lamb waves in FGPM plate. The obtained numerical results can be used to design different sensors with high performance working at different frequency ranges by adjusting the extent of the gradient property.

Guided modes modelling in viscoelastic multilayered composites

Due to the periodicity of the composite structure the Floquet wave approach seems well suited for multilayered medium characterization. The pass and stop band domains for [0/45/90/-45] cross ply composites have been plotted. Dispersive guided wave propagation through a lossy composite laminates immersed in water have been investigated. Our interest is focused on a guided mode inside the frequency range from 1.6 MHz to 5 MHz. Within the considered frequency range, these modes have been pointed out by both reflection coefficient and density of energy analysis in term of incident angle. In this paper it is investigated how by fine-tuning the frequency and the incident angle, internal displacement and stress field vary in the multilayer. When the frequency is increased the mode changes from a plate mode to a surface mode. The description includes real Floquet wave numbers as well as complex wave numbers.

Influence of attenuation on the behavior of refracted elastic waves at the interface between anisotropic media

During the ultrasonic non-destructive evaluation of complex materials, like multilayer or composite materials, the behavior of the ultrasonic waves at the interface of samples is strongly dependent upon the anisotropy as well as the attenuation characteristics of the propagation media. In the generally arbitrary case, the incident wave is assumed to be inhomogeneous. Therefore the application of the Snell-Descartes laws requires to consider the real as well as the imaginary parts of all the quantities encountered during the study. In that aim, we use a representation of the complex slowness curves so-called slowness interface curves which point out the evolution of the interaction of the waves at the interface with the inhomogeneity factors, i.e. the imaginary part of the slowness vectors. The continuous distortion of the curves with the inhomogeneity factor increasing is an interesting approach of these complicated phenomena.