Developments in Ceramic Materials Research

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R. Ramesh, H. Kara, Ron Stevens and C. R. Bowen
characteristics of piezocomposite hydrophones. 3-dimensional FEM studies on 1-3
piezocomposites [23] and 3-3 piezocomposites [39] have demonstrated the importance of
real-sized models.
Before attempting to model the complicated structures of porous piezoceramics, it is
worthwhile to model a dense piezoceramic element of simple geometry and validate the
results with analytical or experimental data. Then, it can be extended to more complicated
geometrical shapes of 3-3 piezocomposites.
Several specialised finite element packages are available to model piezoelectric systems.
Some of the popular and commonly used packages are, ATILA, ANSYS, PAFEC, and
PZFLEX. Each one has its advantages and disadvantages. The multi physics module of
ANSYS offers a convenient way of generating complicated structures and is well suited for
porous piezoceramic systems.
4.1. Model of Dense PZT Discs
Due to the simplicity in geometry, the dense PZT disc hydrophones are modelled by
using 2-dimensional axisymmetric harmonic analysis. Consider a PZT disc of length L and
radius a as shown in Figure 8. Uniform electrodes are coated on the top and bottom flat
surfaces and it is poled in the axial direction. The hydrophone is encapsulated by an
acoustically transparent rubber and is surrounded by water medium. The details of the
axisymmetric model and the finite element mesh are shown in Figure 9. Axisymmetric
coupled-field elements are used for the active material. The model includes the PZT
hydrophone and the surrounding fluid (water) medium.
Figure 8. Geometry of piezoceramic disc modeled. V is the voltage across the electrodes and F 1, F 2 and
F3 are the forces acting on the surfaces.