Artigo Revisado por pares

Elastic waves in periodically layered infinite and semi-infinite anisotropic media

1987; Elsevier BV; Volume: 185; Issue: 1-2 Linguagem: Inglês

10.1016/s0039-6028(87)80618-0

ISSN

1879-2758

Autores

A. Nougaoui, B. Djafari Rouhani,

Tópico(s)

Acoustic Wave Phenomena Research

Resumo

The propagation of elastic waves is studied in infinite and semi-infinite periodically layered media of hexagonal and cubic symmetries. A transfer matrix method is used to obtain a closed-form relation for the dispersion of bulk as well as surface waves in superlattices made of hexagonal crystals with (0001) interfaces. It is shown that the same results can be transposed to propagation of elastic waves in cubic superlattices with (001) interfaces and the k‖ (wavevector parallel to the interfaces) along [100] or [110]. In the limit of long wavelengths compared to the period, the superlattice behaves like an effective medium whose elastic constants can be obtained by averaging over particular combinations of the elastic constants of the two films. In this limit we have studied the velocity of the Rayleigh wave versus the relative thickness of the two constituents; it goes from the Rayleigh wave velocity of one medium to that of the other, but this variation is not necessarily monotonic. Finally, the extension of our formalism to obtain the dispersion relation of a superlattice composed of N different media is discussed and an explicit result is given for the transverse modes.

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