Measurement and FEA Simulation of the Electro-mechanical and Acoustic Response of an Of-the-shelf Open-type Piezoelectric Flexural Ultrasonic Transducer
High power, air-coupled ultrasound has gained significant interest from the research community due to the rise in applications such as non-contact particle manipulation, haptic feedback, and sound steering. A growing number of researchers are utilizing transducers designed for proximity sensing specifically a type of transducer known as an open-type flexural ultrasonic transducer (open-type FUT). This type of transducer has several advantages over Langevin horn transducers, namely they are compact, low cost and have very stable resonant frequencies. These characteristics make open-type FUTs ideally suited for forming large arrays, which allows for greater control of the generated acoustic field.
Despite the growing use of open-type FUTs to produce high power ultrasound in air, there is very little information in the literature about their response characteristics. Furthermore, as far as the authors are aware there is no publicly available information on the break-down of the response of these transducers (into electro-mechanical and acoustic domains as well as individual components) or how the response changes with excitation voltage. There are a large number of low-cost open-type FUTs available, all with very similar rated acoustic properties but little information to determine which is most suitable for specific high power applications. In addition, as these transducers are designed for sensing applications, they can sometimes be utilized outside their rated operating conditions. For these reasons, it would be useful to those in the power ultrasonics research community utilizing open-type FUTs to have more detailed information about their response characteristics.
In this paper, a combination of experimental and multiphysics FEA simulation results are presented to explore the response of a single off-the-shelf open-type FUT. COMSOL Multiphysics® is used to model the full transducer operation, coupling the piezoelectric, structural mechanics and pressure acoustics physics. The model is used to simulate the frequency response of the full transducer, as well as the response of the individual components, which is not easily done experimentally. The simulated response of the full transducer model is also compared to experimental data, which allows for a better understanding of the influence of nonlinearity on system response, which is inherently present in the physical system but can be neglected in simulation.
