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Abstract Propagation of harmonic Lamb waves in functionally graded (FG) plates with transverse inhomogeneity is analyzed by applying the modified Cauchy six-dimensional formalism. For arbitrary transverse inhomogeneity and arbitrary elastic anisotropy a closed form implicit analytical solution for dispersion equation is derived. Dispersion relations for materials with exponential inhomogeneity are obtained. Highlights • Analytical solution for dispersion of Lamb waves in FG plates is derived. • Modification of Cauchy six-dimensional formalism is constructed. • Numerical examples for plates with exponential inhomogeneity are given. [ABSTRACT FROM AUTHOR]

The solution of the complete three-dimensional (3D) guided wave propagation problem in infinite laminated composite plates using a semi-analytical method is presented. The proposed method constructs the problem directly from the 3D governing equations, assuming through-the-thickness layerwise laminate mechanics with linear piecewise variation of all displacement components. The solution is then transformed into the frequency–wavenumber domain, applying sequential Fourier transforms in time and two-dimensional space. Finally, a technique for obtaining the 3D solution via the two dimensional (2D) forced problem is presented. Results for various material systems, such as isotropic, cross-ply and quasi-isotropic composite laminate plates, are shown and compared to well-established analytical results. [ABSTRACT FROM AUTHOR]

Ultrasonic Lamb waves are affected by structural discontinuities (e.g. stiffeners, ribs or joints), and it is necessary to understand the quantitative characteristics of their influence on the waves so that the structural features are not misidentified as defects in nondestructive evaluation (NDE) applications. In this paper, the benchmark problem of Lamb wave reflection at a free end as well as the interaction of Lamb waves with upward and downward step discontinuities is solved using an analytical approach. The free-end problem is considered to show the influence of the decaying waves on the power flow in the plate. In all problems, a near-field solution is obtained, and power flows past the cross-sections of the plate are evaluated. Furthermore, amplitude spectra and results for different step sizes are presented. The analytically derived results are compared with those from transient finite element simulations, showing good agreement. [ABSTRACT FROM AUTHOR]

We investigate the transmission modes in one-dimensional piezoelectric phononic crystal plate, which is consisted of piezoelectric ceramics placed periodically in epoxy. The influences of piezoelectricity and different electrical boundary conditions on the Lamb waves in the composite plate are studied in detail, and an important elastic wave mode named as piezoelectric-sensitive mode (PSM) is defined. Furthermore, the influences of the piezoelectric constants, the filling fraction and the ratio of thickness to lattice pitch on PSM are given, and the physical mechanism of PSM is also discussed. The numerical results show that PSM has a relatively larger frequency shift and significant change in the displacement distribution when piezoelectricity is considered; the electromechanical coupling coefficient of PSM is much larger than the other modes. It reveals that PSM is an important and useful mode in piezoelectric periodic structures. This investigation is helpful in controlling the band gaps and also gives a potential application in design of sensing system and different piezoelectric devices. [ABSTRACT FROM AUTHOR]

Abstract: Quantifying wall thickness in the presence of corrosion damage allows the residual life of plate-like structures to be determined. Guided wave tomography is a solution which allows an area to be imaged with data from an array of ultrasonic transducers around the defect, using tomographic methods to establish wall thickness. We exploit the dispersive nature of Lamb waves travelling through the wall to convert the thickness variation into wave velocity variations, providing a mechanism to determine thickness from a velocity reconstruction. HARBUT (the Hybrid Algorithm for Robust Breast Ultrasound Tomography) has been developed to give high-resolution, accurate and robust reconstructions of ultrasonic velocity through the breast; in this paper we extend the method to generate thickness maps for guided wave tomography. By iterating HARBUT we show that we can improve the accuracy of reconstructions of the small, high contrast defects expected from corrosion, allowing estimates of thicknesses within 1 mm for a 10 mm plate from both simulated and experimental data. [Copyright &y& Elsevier]