  The fundamental shear horizontal (SH0) wave in plate-like structures is of
practical importance in structural health monitoring due to its non-dispersive
characteristics. However, compared with Lamb wave, SH0 wave is less used in
practice since it is difficult to be excited by using conventional
piezoelectric transducers. Recently, face-shear piezoelectric mode has been
realized in PZT ceramics and several face-shear piezoelectric transducers have
been developed to excite pure SH0 wave in plates. However, when controllable
radiation pattern of SH0 wave is required, it is found that no mathematical
basis is available for designers to optimize the transducer's parameters. In
this work, based on the reciprocal theorem of elastodynamics and Huygens'
principle, a theoretical model is proposed to describe the SH0 wave field
generated by arbitrary-shaped face-shear transducers bonded on an infinite
isotropic plate. It is proved that the wave field generated by a face-shear
transducer is equivalent to that generated by uniform in-plane tractions along
its perimeter. Then the proposed model is applied to two specific cases of a
single square face-shear (d24) PZT wafer and a bidirectional SH0 wave
piezoelectric transducer(BSH-PT).Explicit analytical expressions for both cases
are successfully obtained. The accuracy of the obtained analytical model is
verified by both experiments and FEM simulations. Furthermore, some general
guidelines based on the analytical model are presented for optimization of the
transducer's dimensions. Finally, based on the guidelines, a new bidirectional
SH0 wave piezoelectric transducer is proposed with very small beam divergence.
