Abstract
Guided waves, especially Lamb waves or shear-horizontal waves, are widely used types of waves for ultrasonic inspection of large structures. Well known property of guided waves is their dispersive character, which means that the propagation velocity of the particular wave mode is not only a function of physical properties of the material, in which the wave propagates or the wave´s frequency, but also depends on the geometry of the structure in itself. Dispersion curves provide us the information related to the dependency between the wavenumber and the frequency of the particular mode and can be obtained by a numerical solution of Rayleigh-Lamb frequency equation. A solution of Rayleigh-Lamb frequency equation forms for a given frequency and plate thickness a set of a finite number of real and pure imaginary wavenumbers and an infinite number of complex wavenumbers. Proposed paper presents a complete procedure of how to obtain all three kinds of wavenumbers for a given geometry and frequency interval. The main emphasis is placed on the effectiveness of the procedures, which are used for finding the roots of dispersion equation for all three kinds of wavenumbers.
Highlights
Ultrasonic testing is, besides eddy current testing method, one of most commonly used nondestructive techniques in the case of inspection of plate-like structures [1]
The main scope of the article is to present fast and robust procedure for calculation a set of real, imaginary and complex wavenumbers, which are the roots of dispersion equation, for wide range of frequency thickness product
It has to be noted, that the dispersion curves were constructed for aluminium plate of cL = 6300 m/sec, cT = 3100 m/sec and the thickness of the plate was equal to 8 mm
Summary
Ultrasonic testing is, besides eddy current testing method, one of most commonly used nondestructive techniques in the case of inspection of plate-like structures [1]. The structure of the particular mode of guided Lamb wave in itself is relatively complex compared to the longitudinal or transversal bulk waves. This fact appears to be an advantage, since it is possible to select a particular mode shape in order to increase the. This advantage, is directly related with increased complexity of the results interpretation. The main feature of guided Lamb waves is their dispersive character, defined by dispersion curves, which describe us the dependency between the wavenumber and the frequency of particular wave mode for given geometry. The main scope of the article is to present fast and robust procedure for calculation a set of real, imaginary and complex wavenumbers, which are the roots of dispersion equation, for wide range of frequency thickness product
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