Abstract
The “wedge” method of generating guided waves in isotropic layers was analyzed both theoretically and experimentally by Viktorov et. al, in 1965 [1]. The main parts of the work were later reproduced in Viktorov’s now famous book on Rayleigh and Lamb waves [2]. Of several detailed observations made in these investigations, one was that: For optimal generation of a mode of a given wavenumber, k, the angle of the wedge should be “in the neighborhood” of the Snell’s law angle, θ i = sin−1(k/k w), where k w represents the wavenumber of the wave in the wedge[2]. Such a choice of incident angle was being used by experimentalists utilizing Lamb waves for nondestructive evaluation purposes [3–5] even before Viktorov’s analysis. The use of such an angle no doubt arose from the theory of (infinite) plane wave reflection/refraction at planar interfaces. In those cases, which are strictly of academic interest or for approximating real experimental conditions, Snell’s law holds exactly as a result of satisfaction of boundary conditions along the entire (infinite) interface.
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References
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The factor ∣R(θi)∣ in [7] has thus been set equal to unity.
It can be shown by differentiating Eq. (2) with respect to θ i and taking the limit as θ i → sin−1(k v //k w ), that A v z;É,θ i ) is not a maximum at the Snell’s law angle. The actual maximizing angle is, however, generally very close to this angle.
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© 1995 Plenum Press, New York
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Ditri, J.J., Rajana, K.M. (1995). Analysis of the Wedge Method of Generating Guided Waves. In: Thompson, D.O., Chimenti, D.E. (eds) Review of Progress in Quantitative Nondestructive Evaluation. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-1987-4_17
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DOI: https://doi.org/10.1007/978-1-4615-1987-4_17
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