Multiple zero group velocity Lamb modes in an anisotropic plate: propagation along different crystallographic axes

Abstract

This paper studies the propagation of symmetric and antisymmetric Lamb waves along a 1 mm thick iodic acid plate (HIO3) in the 1–50 MHz frequency range. The Lamb mode propagation along three crystallographic planes was theoretically investigated, for two mutually orthogonal propagation directions. Several frequencies were found that correspond to Lamb modes with zero group velocity (ZGV) and non-null phase velocity values. The first symmetric Lamb mode, S1, was found to possess only one ZGV point, regardless of the propagation direction; higher order symmetric and antisymmetric modes with up to four ZGV points were found, depending on the propagation plane. The dependence of the ZGV frequencies on each elastic constant (c11, c13, c33, c55) of the HIO3 plate material was also investigated by changing the constant values by 5% and 10%. It was found that c33 and c55 affect the number of the ZGV points, while c11 and c13 affect the frequency of the ZGV points. The existence and frequencies of the ZGV points are strongly dependent on the proximity of standing longitudinal and transverse waves at nearby cutoff frequencies.

Optimization of coupled Lamb wave parameters for defect detection in anisotropic composite three-layer with Kelvin-Voigt viscoelasticity using Legendre polynomial method

“…In order to achieve non-destructive testing and aging controls for composite materials, there is a need for more suitable and reliable non-destructive evaluation methods. By virtue of their sensitivity to defects and the possibility to let them probe parts of components that are difficult to reach, Lamb waves have been proven to have a great potential for implementation in applications of structural health monitoring [3,4]. Effective use of Lamb wave based approaches for such a purpose largely depends on developing a good understanding of the mechanics of wave propagation in composite laminates [5].…”

“…Fig 4. Phase velocity (a) and attenuation (b) spectrum of the A2 mode in [0/60/0] carbon epoxy plate for different numbers of Legendre polynomial terms M and calculated by the stiffness matrix method.…”