Ultrasonic beam distortion in transversely isotropic media

The distortion of beam profiles and skewing of beam energy observed in transmission of ultrasound into a transversely isotropic medium can lead to erroneous interpretations of NDE data for materials such as columnar-grain steels and fiber-reinforced composites. In this paper, results are presentd for the numerical evaluation of the exact Fourier integral representation of transmission of an arbitrary incident field from an isotropic into a transversely isotropic half-space. The problem is fully three-dimensional, i.e., the symmetry axis of the transversely isotropic material is oriented arbitrarily relative to the half-space boundary and angles of incidence. The cases chosen for numerical study were selected from previously unexplained experimental data obtained from the study of propagation in columnar grain steels (welds), and from situations commonly encountered during the inspection of fiber-reinforced composites. Experimental results which give evidence to the numerically observed phenomena are presented. 11 refs., 4 figs