Finite Element Modeling for Ultrasonic Transducers (Preprint)

Finite element modeling is being adopted in the design of ultrasonic transducers and imaging arrays. Impetus is accelerated product design cycles and the need to push the technology. Existing designs are being optimized and new concepts are being explored. This recent acceptance follows the convergence of improvements on many fronts: necessary computer resources are more accessible, lean, specialized algorithms replacing general-purpose approaches, and better material characterization. The basics of the finite element method (FEM) for the coupled piezoelectric-acoustic problem are reviewed. We contrast different FEM formulations and discuss the implications of each: time-domain versus frequency domain, implicit versus explicit algorithms, linear versus nonlinear. Beyond discussions of the theoretical underpinnings of numerical methods, the paper also examines other modeling ingredients such as discretization, material attenuation, boundary conditions, farfield extrapolation, and electric circuits. Particular emphasis is placed on material characterization, and this is discussed through an actual model-build-test validation sequence, undertaken recently. Some applications are also discussed. Presented at the SPIE International Symposium on Medical Imaging, held in San Diego, CA, on 21-27 Feb 1998. The original document contains color images.