Ultrasonic model studies of Rayleigh wave scattering

Abstract

The effects of surface irregularities on the propagation of Rayleigh waves are studied using two‐dimensional seismic ultrasonic models. Specially designed contactless transducers (Chamuel, U.S. Patent Number 4,035,762, July 1977), in the form of electromagnetic coils, were used to generate and detect the ultrasonic waves in magnetostrictive sheets. The contactless transductions are based on the Joule and Villari effects. One type of transducer consisting of a folded circular coil was used to detect the longitudinal component of the surface waves propagating along the edge of the magnetostrictive sheet. A second type of transducer was used to measure the body wave generated by the surface waves upon reflections from the surface irregularities. Several shapes such as steps, ramps, pyramids, and rectangular obstacles were machined along the edges of the magnetostrictive sheets. Nickel 200 was chosen for the experiments. The data obtained from the experiments clearly showed the transmission. reflection, and mode conversion of the wave at the boundaries. The dimensions of the surface irregularities were comparable to the dominant wavelength.