Novel horn designs for power ultrasonics

Abstract

Ultrasonic horns are used in a variety of industrial and medical applications. At JPL, a rock-sampling tool based on an ultrasonic horn was developed to drill, abrade and core rock samples, including hard basalts. This device is an impact device, which uses ultrasonic vibrations that occur at the horn tip to produce a sonic resonance with the aid of a loosely connected mass. Although standard horns are found in many current industrial designs, they suffer from a few key limitations when used for USDC (ultrasonic/sonic driller/corer) applications. Manufacturing a horn requires turning down stock material (e.g., titanium) from the larger outer diameter to the horn tip diameter, and this process is both time consuming and wasteful. We present novel horn designs that are specifically designed for impact applications such as USDC. One such design addresses the excessive length that is involved with the use of the horn, limiting its applications when system dimensions are constrained. For this purpose, a folded horn design was conceived that reduces the overall length of the resonator (physical length) but maintains or increases the acoustic length. Initial experiments with horns having such a design indicate that the tip displacement can be further adjusted by phasing the bending displacements and the extensional displacements. Another conceived horn design is the dog-bone horn that uses an end mass on the horn tip to increase the impact efficiency of the horn. Experimental results for these novel horn designs are presented and compared to the results predicted by theory.