Ultrasonic methodologies of air-coupled guided waves, birefringent shear waves, and nonlinear ultrasound are presented and applied to the characterization of aerospace materials. The guided waves generated by air-coupled ultrasound provide non-contact monitoring of in-plane stiffness anisotropy and high-contrast imaging of defects in a single-sided access configuration. Mapping of local fibre o...

Under certain circumstances, Voigt waves can propagate in a biaxial composite medium even though the component material phases individually do not support Voigt wave propagation. This phenomenon is considered within the context of the strong– permittivity–fluctuation theory. A generalized implementation of the theory is developed in order to explore the propagation of Voigt waves in any directi...

The propagation of bend and shear waves through an elastic rod is investigated in the framework of geometrically exact nonlinear elasticity. The model allows for shear, extension/compression, bend and twist thus enabling the study of the dynamics of all types of elastic deformations. Numerical and analytical solutions demonstrate that the propagation of planar bend or shear disturbances of fini...

The propagation of shear waves in an anisotropic fluid saturated porous layer over a prestressed semi-infinite homogeneous elastic half-space lying under an elastic homogeneous layer with irregularity present at the interface with rigid boundary has been studied. The rectangular irregularity has been taken in the half-space. The dispersion equation for shear waves is derived by using the pertur...

We present a spectral linear analysis in terms of advected Fourier modes to describe the behavior of a fluid submitted to four constraints: shear (with rate S), rotation (with angular velocity Ω), stratification, and magnetic field within the linear spectral theory or the shearing box model in astrophysics. As a consequence of the fact that the base flow must be a solution of the Euler-Boussine...

If nonhydrostatic internal waves are of sufficiently large amplitude, they undergo significant dispersion due to interactions between the waves and wave-induced mean flow. The effect of these interactions is investigated for internal waves propagating upward in a uniformly stratified Boussinesq flow with uniform shear. The sign of the shear is established so that the wave intrinsic frequency in...

The three-dimensional linearized optimal energy growth mechanism, in plane parallel shear flows, is re-examined in terms of the role of vortex stretching and the interplay between the spanwise vorticity and the planar divergent components. For high Reynolds numbers the structure of the optimal perturbations in Couette, Poiseuille and mixing-layer shear profiles is robust and resembles localized...

This paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the closed form. Some particular cases have been discussed and in one special case the relation obtained is in agreement with existing r...