OPTICAL TECHNIQUES TO EXAMINE THE SCATTERING OF RAYLEIGH SURF ACE W AYES Douglas A. Bruttomesso Graduate Research Assistant School of Civil and Environmental Engineering Georgia Institute of Technology Atlanta, GA 30332-0355 Laurence 1. Jacobs Associate Professor School of Civil and Environmental Engineering Georgia Institute of Technology Atlanta, GA 30332-0355 INTRODUCTION This paper presents the results of an experimental investigation of the interaction of Rayleigh waves with corners. The experiments are done with a dual probe interferometer to measure the interaction of a normal incident Rayleigh wave with corners of varying angles. The incident Rayleigh waves are optically generated with a pulsed laser. The effects of the corners on the Rayleigh waves are then characterized and a finite impulse response (FIR) filter is designed to remove them. In nondestructive evaluation of surface flaws, the change of amplitude and frequency of a Rayleigh wave is characteristic of the size and depth of the flaw. Unfortunately, any change in the surface contour of a specimen will also change the amplitude and frequency content of a Rayleigh wave. Because the geometry of the specimen being investigated affects the frequency content of the Rayleigh wave, it becomes very difficult to discern any effects due to a surface defect, and thus hard to detect surface flaws. Previous researchers have investigated the interaction of Rayleigh waves with geometric features such as corners. Viktorov [1] examined the interaction of an incident, harmonic Rayleigh wave with corners of various angles. He showed that the combination of the incident, reflected and transmitted Rayleigh wave does not satisfY the stress free boundary condition; part of the incident Rayleigh wave is mode converted at corners into longitudinal and shear waves that propagate into the body Recent experimental and numerical modeling of the scattering of the incident Rayleigh wave by a 90° angle (quarter space) includes the work by Li et. al [2], Bond [3], Gautesen[4], and Kima and Vu [5]. Review of Progress in Quantitative Nondestructive Evaluation, Vol. 15 Edited by D.O. Thompson and D,E. Chimenti, Plenum Press, New Yark, 1996 651