3-D Modeling of Ultrasonic Scattering from Intergranular Stress Corrosion Cracks

Abstract

This paper describes the derivation of a three-dimensional model for scattering of elastic waves by an intergranular stress corrosion crack (IGSCC). The model is based on a geometrical abstraction of the IGSCC. The crack has a main stem and left and right branches. The transducer is on the upper surface and the crack breaks the lower surface of a flat plate. The beam of transverse wave motions radiated by the transducer insonifies the crack under an angle of 45° with the lower face of the plate. Figure 1 shows the plane of symmetry of the configuration. The current profile of the beam is Gaussian, but the use of other beam profiles is possible. The position of the center of the transducer can be varied in the plane of symmetry of the crack. This allows the simulation of sizing techniques which require probe motion. The backscattered field has been computed by using the Kirchhoff approximation for the crack opening displacements of the individual components of the branched crack. The backscattering by the main stem and the branches has been analyzed and superimposed to provide the total backscattered field in the frequency domain. Numerical results are presented.