ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

5aPA5. Geometrical theory of diffraction applied to Scholte wave diffraction.

H. Duflo

A. Tinel

J. Duclos

Lab. d'Acoustique Ultrasonore et d'Electronique, U.R.A. C.N.R.S. 1373, Universite du Havre, Place R. Schuman, 76610 Le Havre, France

The geometrical theory of diffraction (GTD) has been established by Keller in order to describe the interaction of a bulk wave with a dihedral edge. It was experimentally verified that Keller's laws were also valid to describe the interaction of a Scholte wave with the edge of an elastic dihedral. When the Scholte wave met the dihedral at oblique incidence, the diffracted energy was actually on Keller's cone the axis and generatrix of it were respectively the dihedral edge and the direction of the incident Scholte wave. It was assumed that incident energy spread among a bulk wave in the direction of the incident Scholte wave as well as reflected and transmitted surface waves (Scholte and Rayleigh waves). The direction of emission of these waves was calculated as a function of dihedral and incidence angles. This calculus showed that Rayleigh waves did not exist if the incidence angle was higher than the Rayleigh angle. Experimental results were obtained for duraluminum dihedrals of various angles ranging from 30 to 90 deg and for incidence directions between 0 and 45 deg. Diffracted energy was only noted on Keller's cone. [Work supported by D.R.E.T.]