Design of ultrasonic longitudinal-torsional vibrator based on waveguide principle for manufacturing and medical applications

This paper presents a new design of an ultrasonic vibrator that transforms longitudinal vibration into torsional vibrations for both manufacturing and medical applications. Conventional design methods of the ultrasonic vibrators are difficult to achieve complex hybrid vibration due to the limit of traditional straight shape and the tedious machining processes in fabrication. To overcome the disadvantages, this paper presents a new design of a hybrid longitudinal-torsional (L&T) ultrasonic vibrator. The hybrid L&T vibrator was designed using the acoustic waveguide principle and successfully transform the longitudinal vibration into a harmonic torsional vibration on the sample plane. An analytical finite element modeling was conducted for optimizing the hybrid L&T design parameters. Due to the complex design geometry, the new L&T design is difficult to be manufactured by conventional machining processes. Selective laser melting additive manufacture (SLM-AM) was used to fabricate the new hybrid L&T vibrator design. The designed hybrid longitudinal-torsional (L&T) vibrator was driven by axially polarized piezo-ceramic stacks for ultrasonic vibration applications. The experiments validate that the developed L&T vibrator is able to deliver high-energy efficiency vibration in both the longitudinal and the torsional directions. The presented new design of L&T ultrasonic vibrators can be used for applications of ultrasonic machining, surgical bone drilling, high efficient ultrasonic motors, or vibrational needle insertions or surgical tools for medical treatments.