Smart cymbal transducers with nitinol end caps tunable to multiple operating frequencies

Cymbal flextensional transducers have principally been adopted for sensing and actuation and their performance in higher power applications has only recently been investigated. Nitinol is a shape-memory alloy (SMA) with excellent strain recovery, durability, corrosion resistance, and fatigue strength. Although it has been incorporated in many applications, the implementation of nitinol, or any of the SMAs, in power ultrasonic applications is limited. Nitinol exhibits two phenomena, the first being the superelastic effect and the second being the shape-memory effect (SME). This paper assesses two cymbal transducers, one assembled with superelastic nitinol end caps and the other with shape-memory nitinol end caps. Characterization of the nitinol alloy before the design of such transducers is vital, so that they can be tuned to the desired operating frequencies. It is shown this can be achieved for shape-memory nitinol using differential scanning calorimetry (DSC); however, it is also shown that characterizing superelastic nitinol with DSC is problematic. Two transducers are assembled whose two operating frequencies can be tuned, and their dynamic behaviors are compared. Both transducers are shown to be tunable, with limitation for high-power applications largely being associated with the bond layer.