Modelling the propagation and scattering of elastic waves in inhomogeneous anisotropic media

Abstract

A finite-difference numerical model for studying the propagation and scattering of elastic waves in three-dimensional inhomogeneous and anisotropic media of arbitrary symmetry is presented. The model takes account of short pulses and finite-width beams and incorporates mode conversion at boundaries. The model, called SWAM3D (scattering of elastic waves in inhomogeneous anisotropic media in 3D), can handle a region of size equivalent to 250*250*250 nodes, that is a cube of side 25 shear wavelengths. It runs on a CRAY-2 supercomputer and represents a significant advance in the numerical treatment of wave propagation and scattering in inhomogeneous and anisotropic materials. As an indication of the power of the model, it is applied to the scattering of elastic waves of different polarisations from a cylindrical hole in a homogeneous transversely isotropic material. The propagation and scattering of elastic wave in inhomogeneous materials is an important problem in ultrasonic inspection of welds in liquid-metal-cooled fast reactors. A-scans and differential scattering cross sections are presented. They are used to explain some experimental results in the ultrasonic inspection of austenitic welds. The present results confirm the validity and applicability of the model.