Volume 118, Issue 5, November 2005
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
On three-dimensional edge waves in semi-infinite isotropic plates subject to mixed face boundary conditions118(2005); http://dx.doi.org/10.1121/1.2062487View Description Hide Description
This paper is concerned with the propagation of three-dimensional waves localized near the edge of a semi-infinite elastic plate subject to mixed face boundary conditions. In the linear isotropic case it is shown that the problem is closely related to that of Rayleigh surface wave propagation along the free surface of the corresponding half-space. The cut-off frequencies of the analyzed edge waves coincide with the natural frequencies of the associated cross-sectional semi-infinite strip. It is also demonstrated that the eigenspectrum of a rectangular rod can be expressed in terms of the considered three-dimensional waves. The results are then generalized to a prestressed isotropic incompressible material. It is noted that the density of the edge wave spectrum is strongly influenced by the prestress. It is illustrated that the areas of negative group velocity may exist for large primary deformation. Long-wave asymptotic expansions in the vicinity of the cut-off frequencies are presented.
118(2005); http://dx.doi.org/10.1121/1.2062648View Description Hide Description
The three-phase self-consistent (SC) micromechanical model of Cherkaoui et al. [J. Eng. Mater. Technol.116, 274–278 (1994)] is employed to model the anisotropic effects induced by identically oriented, coated, and ellipsoidal microinclusions embedded in a viscoelastic matrix. Numerical predictions of the lossy and anisotropic behavior of the viscoelasticcomposite material are obtained. This study is an extension of a previous paper [J. Acoust. Soc. Am.112 (5), 1937–1943 (2002)], where the agreement of the micromechanical approach with the long wavelength scattering model of Baird et al. [J. Acoust. Soc. Am.105 (3), 1527–1538 (1999)] was demonstrated for the case of spherical inclusions. The use of the SC model for the special case of a biphase effective material is also considered and compared with the complex bounds available in the literature. Parametric studies are presented for the transmission loss in the 0– frequency range of a thick composite material slab containing oblate spheroidal inclusions of varying aspect ratios when the slab is submerged under water. The results are compared with the case of an isotropic composite material having identical constituent material properties and volume fractions.
Computation of the temperature distortion in the stack of a standing-wave thermoacoustic refrigerator118(2005); http://dx.doi.org/10.1121/1.2063087View Description Hide Description
The numerical computation of the flow and heat transfer in the vicinity of a stack plate in a standing waverefrigerator is performed. Temperature distortion is observed, which appears only in the stack region, even if the acoustic standing wave outside the stack is itself sinusoidal. The distortion takes place above the whole plate surface when the length of the plate is equal to or shorter than four times the particle displacement. This condition may occur at high drive ratios and is favored by plate positions close to the velocity antinode. The thermal distortion decreases the thermoacoustic heat pumping along the plate. At high drive ratios, if the length of the plate is not large enough, the thermal distortion can typically explain a difference of about 10% between the calculated heat flux and the heat flux predicted using linear theory.