Love wave propagation in functionally graded piezoelectric material layer

Ningbo University, Ning-po, Zhejiang Sheng, China
Ultrasonics (Impact Factor: 1.94). 04/2007; 46(1):13-22. DOI: 10.1016/j.ultras.2006.09.004
Source: PubMed


An exact approach is used to investigate Love waves in functionally graded piezoelectric material (FGPM) layer bonded to a semi-infinite homogeneous solid. The piezoelectric material is polarized in z-axis direction and the material properties change gradually with the thickness of the layer. We here assume that all material properties of the piezoelectric layer have the same exponential function distribution along the x-axis direction. The analytical solutions of dispersion relations are obtained for electrically open or short circuit conditions. The effects of the gradient variation of material constants on the phase velocity, the group velocity, and the coupled electromechanical factor are discussed in detail. The displacement, electric potential, and stress distributions along thickness of the graded layer are calculated and plotted. Numerical examples indicate that appropriate gradient distributing of the material properties make Love waves to propagate along the surface of the piezoelectric layer, or a bigger electromechanical coupling factor can be obtained, which is in favor of acquiring a better performance in surface acoustic wave (SAW) devices.

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    • "Additionally the manufacture of such high performance devices, layered structures involving functional materials are also considered. The propagation of Love wave in elastic or piezoelectric materials has been investigated by many researchers [3] [4] [5] [6]. Li et al. [7] delivered his idea on the propagation of Love waves in functionally graded piezoelectric materials. "
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    ABSTRACT: 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. Copyright © 2015 Elsevier B.V. All rights reserved.
    Ultrasonics 05/2015; 61. DOI:10.1016/j.ultras.2015.04.011 · 1.94 Impact Factor
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    • "In this work, we use the ' * ' and ' ' symbols to distinguish the different parameters associated with the outer portions x 1 < 0 and x 1 > H, respectively. In the left region x 1 < 0, the governing equations for u * and ϕ * are [13] [14] "
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    ABSTRACT: The effect of functional graded piezoelectric materials on the propagation of thickness-twist waves is investigated through equations of the linear theory of piezoelectricity. The elastic and piezoelectric coefficients, dielectric permittivity, and mass density are assumed to change in a linear form but with different graded parameters along the wave propagation direction. We employ the power-series technique to solve the governing differential equations with variable coefficients attributed to the different graded parameters and prove the correction and convergence of this method. As a special case, the functional graded middle layer resulting from piezoelectric damage and material bonding is investigated. Piezoelectric damaged material can facilitate energy trapping, which is impossible in perfect materials. The increase in the damaged length and the reduction in the piezoelectric coefficient decrease the resonance frequency but increase the number of modes. Higher modes of thickness-twist waves appear periodically along the damaged length. Moreover, the displacement of the center of the damaged portion is neither symmetric nor anti-symmetric, unlike the non-graded plate. The conclusions are theoretically and practically significant for wave devices.
    Smart Materials and Structures 08/2013; 22(9):095021. DOI:10.1088/0964-1726/22/9/095021 · 2.50 Impact Factor
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    • "In the current study, we assume that all material parameters in the functionally graded electro-magneto-elastic substrate have the same exponential function variation along the x-axis (Qian et al., 2009; Du et al., 2007), which are expressed as follows: "
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    ABSTRACT: Bleustein–Gulyaev (B–G) waves in a functionally graded transversely isotropic electro-magneto-elastic half-space, in which all parameters exponentially change along the depth direction, are investigated, and the dispersion equations with respect to the phase velocity for electromagnetically open and shorted conditions are obtained. The B–G waves are dispersive because of the inhomogeneity of the material, which is different from a pure substrate. The graded coefficient exhibits different effects on the B–G waves at different electromagnetic circumstances. With the intervention of the functionally graded material, the electro-magneto-mechanical coupling factor can be improved and the penetration depth of the B–G waves can be decreased. The results can be used in the design of high-performance surface acoustic wave devices.
    European Journal of Mechanics - A/Solids 01/2013; 37:17–23. DOI:10.1016/j.euromechsol.2012.04.004 · 1.68 Impact Factor
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