SOME RESULTS ON THE SCATTERING OF GUIDED ELASTIC SH-WAVES FROM MATERIAL AND GEOMETRIC WAVE-GUIDE DISCONTINUITIES

The scattering of guided elastic SH waves from step discontinuities in the material properties and/or geometry of otherwise uniform Bat laye r waveguides is analytically/numerically analyzed. Analytical results for the case of a step discontinuity in material properties in a layer of uniform thickness an presented for comparison with later numerical results, The case of a sudden change in thickness of the waveguide, p ossibly in conjunction with a change in material properties, is solved numerically. The solution is based on an expansion of the wave fields on either side of the discontinuity in terms of the normal modes perm issible in the analogous infinite layer and subsequent determination o f the modal expansion coefficients. A ''non-coupling'' condition is pr oposed and proven which explains why particular modes are not generate d in the scattering process. A ''perfect-coupling'' condition is also introduced, and the exact transmission amplitude of any mode satisfyin g the condition is given explicitly. (C) 1996 Acoustical Society of Am erica.