Development of a computer model for an ultrasonic polymer film transducer system

Abstract A piezoelectric polymer film such as polyvinylidene fluoride (PVDF) offers the possibility of making cheap ultrasonic transducers which can be permanently bonded to structures for NDE applications. However, before this can be achieved it is necessary to have a full understanding of the behaviour of PVDF in the context of a transducer application. This paper describes the development of an interactive computer program to implement a one-dimensional model of a thin film transducer system mounted on a solid substrate. Starting from a typical transducer system mounted on a solid substrate. Starting from a typical tranducer equivalent circuit, this paper explains how that circuit can be expanded into a complete model representing a PVDF transducer with one or more backing layers bonded to an arbitrary solid substrate. The computer program uses this model to provide immediate predictions of electrical input impedence, acoustic response and pulse-echo response. A series of experiments has been performed using PVDF transducers bonded to a variety of materials in order to validate the model. This has enabled the degree of accuracy required for various parameters within the model, such as mechanical and dielectric loss values, to be assessed. Once validated, the model has been used as a tool to predict the effect of physical parameters, such as bond and electrode thickness, on the performance of a transducer.