Applications of SH Mode for Measurement of Anisotropic Properties of Solids
Baker, A. Richard
Shear-horizontally (SH) polarized transverse (T) modes are uncoupled from the longitudinal (L) (quasilongitudinal (QL)) mode and transverse (quasitransverse (QT)) mode of shear-vertical (SV) polarization, which are generally coupled with each other. This offers certain advantages to using the SH modes for investigation of the phenomena related to the arrivals of transverse modes, because their arrival and amplitude are not affected by the preceding arrivals of the L (QL) modes and the head waves (HW) in some directions and therefore can be clearly identified and measured in the signal generated by a small pointlike source (PS). In this work the SH modes propagating inside a specimen are generated using a pointlike or a line-segment shear (S) mode piezoelectric Pb(Zr,Ti)O3 (PZT) transducer attached on the surface of a (001)-oriented cubic silicon disk, a (001)-oriented transversely isotropic zinc disk, and a thin orthorhombic poly ether ether kethon (PEEK) composite plate oriented in a principal symmetry plane. The SH modes are detected on the surface of the specimen by a pointlike S mode PZT detector which is polarized in the same direction as the source transducer. A novel technique using the SH modes for measurements of shear elastic moduli, such as C 44, C 55, and C 66, is presented for all these specimens. Investigated also using the SH modes is a focusing of fast transverse (FT) modes in silicon. The focusing pattern in silicon is in sharp contrast to the SH mode radiation pattern observed in an isotropic glass plate.