Leaky Lamb waves are important research topics in the area of NDE and acoustic wave sensing technology. For waves propagating in a piezoelectric plate immersed in a fluid (dielectric or conductive), both mechanical and electrical loading effects present and result in phase velocity variation and wave attenuation. To quantitatively characterize these loading effects play an important role in var...

We demonstrate the experimental realization of a multiresonant metamaterial for Lamb waves, i.e., elastic waves propagating in plates. The metamaterial effect comes from the resonances of long aluminum rods that are attached to an aluminum plate. Using time-dependent measurements, we experimentally prove that this metamaterial exhibits wide band gaps as well as sub- and suprawavelength modes fo...

Piezoelectric wafer active sensors (PWAS) are inexpensive, non-intrusive un-obtrusive devices that can be surface-mounted on existing structures, or inserted in a new composite structure. The PWAS can be used in both active and passive modes. In active mode, the PWAS generate Lamb waves that can exist as either traveling waves or standing waves. As traveling waves, PWAS-generated Lamb waves can...

Acoustoelasticity, or the change in elastic wave speeds with stress, is a well-studied phenomenon for bulk waves. The effect of stress on Lamb waves is not as well understood, although it is clear that anisotropic stresses will produce anisotropy in the Lamb wave dispersion curves. Here the theory of acoustoelastic Lamb wave propagation is developed for isotropic media subjected to a biaxial, h...

There are many advantages to adhesively bonding stiffeners onto aircraft structures rather than using traditional mechanical fastening methods. However there is a lack of confidence of the structural integrity of adhesively bonded joints over time. Acousto-ultrasonic Lamb waves have shown great potential in structural health monitoring applications in both metallic and composite structures. Thi...

This paper is focused on the problem of mode identification of Lamb waves in ultrasonic testing, and the principle and process of two time-frequency transform method, smooth pseudo Wigner–Ville distribution and two-dimensional Fourier transform, were discussed. The experimental work were carried out in aluminium plates, and the single and multimode Lamb waves were excited by 5MHz oblique incide...

Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide f...

The aging world-wide aviation fleet requires methods for accurately predicting the presence of structural flaws that compromise airworthiness in aircraft structures. Nondestructive Evaluation (NDE) provides the means to assess these structures quickly, quantitatively, and noninvasively. Ultrasonic guided waves, Lamb waves, are useful for evaluating the plate and shell structures common in aeros...

The capability of embedded piezoelectric wafer active sensors (PWAS) to excite and detect tuned Lamb waves for structural health monitoring is explored. First, a brief review of Lamb waves theory is presented. Second, the PWAS operating principles and their structural coupling through a thin adhesive layer are analyzed. Then, a model of the Lamb waves tuning mechanism with PWAS transducers is d...

With an increasing use of adhesively bonded joints in the industry, there is a correspondingly growing need for the inspection of adhered joints. It is necessary to detect defects in the adhesively bonded materials such as voids inclusions, chemical miscure of the adhesive, or delaminations of the bonded layers. In order to use an ultrasonic technique to detect these defects, a thorough underst...