ECHO STRUCTURE OF SOUND SCATTERING BY A FINITE ELASTIC CYLINDER IN WATER

This paper investigates the echo structure of a short pulse from a finite solid elastic circular cylinder.It is emphasized that in the case of oblique incidence the echoes still include two kinds of the scattering waves:(1).Geometrical scattering waves,namely corner waves.(2).Elastic scattering waves,i.e.the waves related with the elasticity of the cylinder.The geometrical scattering waves are the waves reflected from discontinuities of the cylinder,and essentially independent of the material of the cylinder.Using Kirchhoff approximation the whole representation of corner waves from rigid cylinder has been derived.In the case of oblique incidence the elastic scattering waves differ from the circumferential waves for an infinite cylinder.Two sorts of echoes caused by the reradiation of elastic surface wave have been observed in experimentation:the radial surface backscattering wave and the longitudinal surface backscattering wave.They can be identified according to the arriving time and appearing angle,and the results of a comparable observation in the air.They are caused by the reradiation of Rayleigh wave propagating along the radial surface or the longitudinal surface in the backward direction.