Angular influence on the scattering of fundamental shear horizontal guided waves by a through-thickness crack in an isotropic plate

The angular influence on the scattering of cylindrical-crested waves of the fundamental shear horizontal (SHO) guided mode by through-thickness cracks in an isotropic plate is studied in the context of array imaging using ultrasonic guided waves. Finite element simulations are used to obtain trends which are subject to analytical study and experimental confirmation. The influence of the incidence angle on reflection behavior is first studied in terms of two complementary cases, that of normal incidence and that of specular reflection at various oblique incidence angles. The normal incidence study suggests that for a given incidence angle, the peak reflection is concentrated around the specular direction, while the oblique incidence studies show that maximum specular reflection occurs in the case of normal incidence. The variation of diffraction with both the angle of incidence and that of monitoring is then taken up and this shows that when the first diffraction from the crack edges can be separated, its angular dependence can be obtained from literature on similar bulk elastic wave scattering problems. (C) 2008 Acoustical Society of America. [DOI: 10.1121/1.2968697]