Abstract:

Of concern are distortionless surface stress waves propagating in a medium which may be nonuniform relative to depth. A similar problem was posed by Burke et al. [Q. Appl. Math. 183--194 (1976)] where a unidimensional electrical ladder network model, nonuniform along the principle axis, was used in the investigation. Presently, a two-dimensional development is given based on Hooke's law and Newton's law leading to the well-known Rayleigh-waves formulation in a uniform medium. It will be seen that broadband high-pass propagation modes exist along the principle surface. As these propagate along the surface, they are accompanied by a phase change, linear with distance, in the frequency domain, and an associated symmetry change, periodic with distance, in the time domain. Applications may be found in high-frequency acousto-optics, in situ ultrasonic monitoring of elongated bodies, high-frequency SAW filters, and whenever surface acoustic waves are employed in an environment of high precision or relatively large distances. [Work supported by ONR.]