ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pEA7. Low-frequency underwater transducer modeling using the direct global stiffness method.

J. Robert Fricke

Mark A. Hayner

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

The direct global stiffness matrix method (DGSM), described by Fricke and Hayner [direct global stiffness matrix method for 3-D Truss Dynamics, submitted to the ASME 15th Biennial Conference on Mechanical Vibration and Noise, 17--21 September 1995], provides an efficient method for analyzing two-dimensional and axisymmetric, low-frequency, underwater, transducer geometries. The DGSM method is a wave-type solution based on the Euler--Bernoulli beam element. The mechanical motion of the transducer element is modeled using a collection of beam elements welded together at joints. By imposing dynamic equilibrium conditions at these joints, a banded symmetric stiffness matrix is formed. The matrix is then solved using Gaussian elimination to find joint displacements and rotations with beam energies calculated on a post-processing basis. The radiation load due to the surrounding water is included using a compact source assumption. Thus fluid loading interaction effects, important for low quality factor transducers, are properly addressed. Analysis of a class IV flextensional transducer is offered as an example of the usefulness of this approach.