Abstract

Introduction: Mode theory was used to investigate the excitation of a Stoneley wave by a bounded bulk wave incident at the down-step of a thin layer on a substrate. The Stoneley wave amplitude has two maxima: at grazing and at Rayleigh angle the phase shift of a Stoneley wave due to an inclusion localized near the surfac of a fluid loaded material has been shown as well. Expressions for the amplitude and phase changes were derived and have been analyzed in two particular cases, namely a thin and thick inclusion. The Stoneley wave phase shift strongly depends on the material constants (densities, transverse and longitudinal velocities), on the dimensions of the inclusion and on the Stoneley wave frequency f in particular. For a thick inclusion the Stoneley wave phase shift is almost proportional to f and does not depend on the inclusion thickness while for a thin inclusion the phase shift is proportional to dLf² Although the amplitude of a Stoneley wave is not sensitive to thin inclusions (opposite to thick inclusions) the phase changes of the Stoneley wave are considerable.

Keywords: Ultrasonic Testing

Source: Conference Proceedings of the 4th International Conference of the Slovenian Society for Nondestructive Testing, 24 - 25 April 1997, Ljubljana, Slovenia.
Pages:51 - 58

Publisher:
Slovenian Society for Nondestructive Testing, Faculty of Mechanical Engineering, Askerceva 6, SLO 1000 Ljubljana, Slovenia. Tel +386 61 177 12 03, Fax +386 61 218 567, Email: janez.grum@fs.uni-lj.si.