A complete finite element model [ for US transducers ]

Some commercially available FEM programs are accurate only in calculating eigenfrequencies. Because basic models do not consider damping and loading imposed by the medium, they cannot accurately compute the absolute amplitude at each node, and therefore, cannot evaluate the strength of each mode and variety of response curves. Materials used for matching layers, isolation and backing will introduce many extra eigenfrequencies due to their softness. Without considering damping in transducers, it is very difficult for basic FEM programs to predict the performance of transducers including these materials. This paper addresses the damping of materials used in transducers and the force imposed by the medium. The electric field in ceramics is considered as a variable. This FEM program can predict complete performance of transducers. We have used the FEM program to design over one hundred models of transducers, including two-mode, wide band and air transducers. Agreement between predicted and measured performance is quite good