OBSERVATION OF THE DISPERSION BEHAVIOR OF SURFACE ACOUSTIC-WAVES IN A WEDGE WAVE-GUIDE BY LASER ULTRASONICS

Wedge (or line) acoustic waves, propagating along the tip of an elastic wedge waveguide, are generated by pulsed YAG laser impact and detected by a wideband optical interferometer. In an ideal infinitely sharp and tall wedge guide, the antisymmetrical flexural (ASF) modes are nondispersive and their energies are mostly confined near the wedge tip. The displacement measurements with the optical probe on metallic wedges show broadband pulsed wave forms of ASF modes. Dispersive behavior of these wave forms, which are not predicted by the theoretical models, are clearly demonstrated. The dispersion curves of the phase velocity are quantitatively deduced by a phase analysis method.