Summary
Investigated is the effect of a surface irregularity on the propagation of waves in an isotropic, elastic plate, the method of perturbation being employed to determine the scattered field to the first order in a small parameter descriptive of the height of the irregularity. While the firstorder displacement field in the region under, and in the immediate vicinity of, the disturbed surface is very complicated, the far field in either direction, generated by either a symmetric or an antisymmetric incident wave, consists of a finite number of propagating waves, symmetric and antisymmetric, their number corresponding to the number of real roots of the frequency equation for the given frequency of incident wave.
The general, analytical, results are then applied to the example of a plate having a small triangular protrusion or indentation on one of its surfaces, and the displacement is displayed in graphical form.
In the course of the investigation it is shown that the roots of the Rayleigh-Lamb frequency equation are symmetrically located about the axes of the reals and imaginaries.
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Sumner, J.H., Deresiewicz, H. Waves in an elastic plate with an irregular boundary. PAGEOPH 96, 106–126 (1972). https://doi.org/10.1007/BF00875633
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DOI: https://doi.org/10.1007/BF00875633