Enhanced resolution phase transformations in a Nitinol cymbal ultrasonic device

Abstract

The traditional form of cymbal transducer is composed of cymbal endcaps bonded to a piezoelectric ceramic, whose radial vibrations drive relatively high amplitude endcap displacements. This transducer has been investigated for sonar and energy harvesting, but recent research has focused on adapting it for higher power applications, such as surgical cutting. In such procedures, there are known challenges in the efficient cutting of different materials, such as bone and muscular tissue, using one device. One viable method is to introduce adaptive dynamic properties, including operating frequency, by fabricating the caps with a shape memory alloy. Here, elastic modulus can be tuned by inducing a phase transformation, allowing rapid control of device dynamics. In this study, the temperature-dependent dynamics of a Nitinol cymbal device are examined using electrical impedance analysis and laser Doppler vibrometry, and practical aspects of introducing Nitinol into such devices are considered. The results show that a mixed austenitic and martensitic microstructure creates intermediate stiffnesses and exhibit the potential to administer minor temperature changes to achieve significant resonance shifts.