SPECIFIC FEATURES OF THE ACOUSTIC DIFFRACTION FROM A PERIODIC SYSTEM OF PLANAR SLIDING-CONTACT INTERFACES
✍ Scribed by A.L. SHUVALOV; A.S. GORKUNOVA
- Book ID
- 102609331
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 387 KB
- Volume
- 243
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
Propagation of sagittally polarized plane acoustic waves is considered in an orthorhombic medium with a periodic system of N#1 in"nite planar cuts maintaining sliding contact (ideal cracks). The re#ection and transmission rates are derived by the propagator-matrix method. Two essentially di!erent types of stop bands exist, in which the imaginary part of the Bloch vector either remains "nite or reaches in"nity. The latter corresponds to the transmission cut-o!, which may come about speci"cally at the sliding-contact interface. Coupling of the Bragg phenomenon with the cutting-o! e!ect produces quite speci"c resonant features of re#ection and transmission. Especially sharp "ltering properties of the spectra come about at a small deviation from such angles of incidence, which provide total transmission (anti-re#ection) independent of frequency, namely, at nearly normal incidence of the fast mode, and at angles of incidence of the slow mode close to a certain critical value. At " "1, the spectrum of transmission (without mode conversion) represents a nearly periodic group of abrupt dips to zero and a modulated group of secondary drops increasing with growing ( )N, whereas the general spectral background is close to unity. In turn, the re#ection spectrum at " "1 contains sharp principal peaks with modulated heights, reaching nearly unit height, and the secondary peaks against almost zero background. Changes in the spectra shape on varying the angle of incidence become drastic near the speci"c threshold value of , which corresponds to the mutual transformation of the ordinary stop bands and cutting-o! bands. After the cross-over, the transmission spectrum contains signi"cantly wide step-wise dips, within which the rate stays very close to zero if N1.