Research on the scattering of ultrasound from crack defects especially in 3D is particularly difficult because of the typical target defect sizes and possible test frequencies, for which often neither the low frequency nor high frequency asymptotic solutions are accurate.  As a result of this, the majority of crack scattering studies have been limited to simple geometric shapes.  However, the scattering behaviour from rough defect is different from that from a crack with a regular shape, as compared in Fig. 1 (a) and (b).

The purpose of the research project is to develop a modelling approach which will deliver accurate and reliable predictions of the elastic wave response from 2D or 3D realistic rough defects at different incidence/scattering angles.  This would enable the developers of inspection procedures to erode the current conservatism in the technical justifications.  The problem is tackled from two complementary directions, one developing new mathematical tools and the other developing reliable procedures for numerical modelling using the hybrid approach.  These numerical tools would be implemented to study how the statistical measures of surface roughness affect scattering waves.  In addition, fundamental wave physics behind the scattering behaviour would be investigated with different crack geometry, statistical description of the roughness, frequency, wave mode, and incidence/scattering angles.

Fig. 1: Elastic wave scattering from a smooth crack and a rough crack with the same geometry and the inclined angle. (a) Scattering field around a smooth crack. (b) Scattering field around a rough crack