Search

Abstract In this study the nonlocal bond-based peridynamic (PD) theory was applied to simulate Lamb wave transmission in 2D bimaterial plates. Plates of unlike materials were jointed end-to-end to make a bimaterial plate. The surface of the plate was then excited tangentially by single-frequency and multi-frequency force signals. The influence of changing material properties on travelling of the symmetric and antisymmetric Lamb waves were studied in detail. The phase and group velocities of travelling wave in bimaterial plates were calculated and it was found that dissimilar material properties of two joint plates can significantly alter the amplitude and arrival time of the wave. Moreover, Fast Fourier Transform (FFT) of the time history of symmetric Lamb wave velocity was calculated and verified. Accuracy and consistency of PD wave model was confirmed entirely using Spectral Finite Element Method (SFEM). The comparison between the results of two applied methods shows a good agreement. [ABSTRACT FROM AUTHOR]

Traditionally dispersion characteristics for any plate structure are evaluated using the Rayleigh-Lamb solution and an assumption that the material properties are known. In cases where the material properties may be difficult to obtain the opposite is proposed. Specifically, the dispersive characteristics of Lamb waves may be used to extract the mechanical properties of a given test coupon. This paper presents a particle swarm optimisation (PSO) methodology to achieve this. The results from a series of tests on an aluminium coupon were used to validate the approach. The PSO was found to successfully match dispersion characteristics identified in a 2D FFT. [ABSTRACT FROM AUTHOR]

Abstract: Propagation of the anti-symmetric fundamental Lamb mode (A 0) in a composite laminate containing a semi-infinite delamination was studied through numerical simulations and experimental studies. Here, the wave was generated on a sub-laminate above the delaminated region, and the reflection and transmission of the Lamb modes at the edge of the discontinuity were quantitatively studied. The wave group (named as ‘turning mode’), which was made to propagate from one side of the delamination to the other side (through delaminations) was captured and its transmission factor was estimated. Reflection and transmission factors of wave groups were estimated for three different laminates – quasi-isotropic, unidirectional and cross-ply, containing delamination at various interfaces across thickness. Propagation of ‘turning modes’ were also captured experimentally, employing air-coupled transducers, in quasi-isotropic laminates containing delaminations at different interfaces. Attenuation compensation was incorporated in the experimental signals to improve the comparison of transmission and reflection factors between numerical simulations and experiments. [Copyright &y& Elsevier]

Abstract: In this paper, the A0 Lamb wave propagating in a thin finite copper plate is investigated to design a new multi-touch tactile instrument, which could localize one or several fingers. The position of index is localized by identifying the absorption signals of Lamb waves when it is in contact with the plate. Statistic models are used to improve the robustness of this interface. An artificial silicone finger is fabricated in the calibration procedure. The multi-touch (two fingers or more) applications using this plate is also presented. [Copyright &y& Elsevier]