  The fundamental shear horizontal (SH0) wave in plates is of great importance
in the field of nondestructive testing (NDT) and structural health monitoring
(SHM) since it is the unique non-dispersive guided wave mode. For practical
applications, a phased array system based on omnidirectional SH0 wave
transducers is most useful as it can cover a wide range of a plate. However, so
far very few omnidirectional SH wave transducers have been developed. In this
work, we proposed an omnidirectional SH piezoelectric transducer (OSH-PT) based
on a thickness poled piezoelectric ring. The ring is equally divided into
twelve sectors and the electric field is circumferentially applied, resulting
in a new thickness-shear (d15) mode. Finite element analysis shows that the
proposed OSH-PT can excite single-mode SH0 wave and receive the SH0 wave only.
Experiments were then conducted to examine the performance of the proposed
OSH-PT. Results indicated that it can generate and receive single-mode SH0 wave
in a wide frequency range with nearly uniform sensitivities along all
directions. Considering its quite simple configuration, compact size and low
cost, the proposed OSH-PT is expected to greatly promote the applications of SH
waves in the field of NDT and SHM.
