Extraction of Complex Wave Numbers of Lamb Waves

Lamb waves have gained increasing attention from the nondestructive testing (NDT) and structural health monitoring (SHM) communities in the past couple of decades. Lamb waves, which are also called plate waves, can propagate in plate-like structures. If the plate is surrounded by water or a viscoelastic material, the waves energy is dissipated in the surrounding medium and therefore, the waves are called Leaky Lamb waves. In order to generate or work with leaky Lamb waves, it is necessary to know the wavenumber of the corresponding wave. The wave number can be real, pure imaginary, or a complex number. The first two are finite numbers but the third one can be infinite. Identification of the wavenumber of a Lamb waves is carried out through a numerical procedure and because of that, it is not possible to find all possible wave numbers. This paper proposes a new method for extraction of wavenumbers of leaky Lamb waves. Using this method, all types of wavenumbers can be identified. The details of this procedure is presented and examples demonstrating the validity of the procedure are presented.

Keywords:

Leaky Lamb wave , Complex wave number , Dispersion curve , wavenumber