FEM modeling and simulation of broadband ultrasonic transducers with randomized inhomogeneous backing material

TL;DR

This paper presents a FEM-based simulation approach for designing broadband ultrasonic transducers with randomized inhomogeneous backing materials, linking material composition to emitted RF signals.

Contribution

It introduces a novel FEM model in Comsol that accounts for inhomogeneous backing materials without impedance-based assumptions, improving design accuracy.

Findings

Bandwidth predictions align with KLM model for 1D cases

Inhomogeneous backing affects transducer bandwidth

Model avoids impedance-based simplifications

Abstract

A FEM application for the accurate design of composite backing of ultrasonic transducers is presented. The idea is to obtain the dependence between the volume ratio of the tungsten powder in an epoxy matrix used as a backing and the final pulsed RF signal emitted by the backed transducer. An inhomogeneous material model for the backing was adopted instead of the classic complex geometrical FEM. The model was developed in Comsol 5.5 using two of its physics interfaces. The first based on classic FEM or continuous Galerkin for ultrasonic propagation in the backing and the second based on a discontinuous Galerkin option for fluid pulsed propagation. In this way it is possible to avoid the use of an impedance-based model. The calculations for the resulting bandwidth are good enough as predicted for Desilets for the 1D case by using the KLM circuital model. We worked in a 2D space, where the transducer face vibration is far away from the assumed piston-like considered by the unidimensional KLM model.