Directivity of quasi-SH0 modes in cubic anisotropic media

Abstract

We studied the zeroth order shear horizontal modes (SH0 modes) and the quasi-SH0 modes in cubic-anisotropic plates and proposed a formula to describe the scattering directivity of these guided wave modes in arbitrary directions. The quasi-SH0 waves has many unique advantages. However, their velocity and amplitude are influenced by the material anisotropy and change with incidence orientation. In our finding, when the guided wave incidence orientation coincides with the material symmetry plane, the quasi-SH0 modes’ amplitudes generated by a uniform force are approximately equal. Otherwise, the amplitudes are significantly smaller. The formula derived by reciprocity consideration explains this phenomenon. We applied the formula to monocrystalline silicon. The results also show that the quasi-SH0 mode is both velocity non-dispersive and directivity non-dispersive in low-fd (frequency thickness product) state. We established an experimental system based on EMATs and verified the theoretical predictions. This paper completes the theoretical basis for damage reconstruction and acoustic imaging by guided waves in complex structures with cubic anisotropy.