Elastic Wave Behaviour in 2-D Acoustic Interface Superlattices of an Altered Phase

The purpose of the paper is to outline a systematic and unified non-local treat-
ment of mode conversion effects associated with an interface superlattice being a 2D
pseudo-array composed of altered phase inclusions (exemplified by impurity clusters)
and located at a solid-solid plane interface. It will be illustrated, in some detail, for
the instructive case of a Stoneley type acoustic wave (SW), incident on a period-
ically nonhomogeneous portion of an interface and partly transformed into bulk
modes propagating in one of the component solid. An analytical model scheme is
constructed, using a variational method combined with the T matrix approach, ap-
propriate for the 2D periodic array treated, and decaying into the depth of this solid
for the structure in a way determined by the array geometry and element 3D pro-
files as well as the boundary conditions at the interface. An apodization (weighting)
to reduce the side-lobes level is incorporated into the structure by appropriately
varying lateral dimensions and the depth of particular scatterers.