Full and half-wavelength ultrasonic percussive drills

Li, Xuan, Lucas, Margaret and Harkness, Patrick (2018) Full and half-wavelength ultrasonic percussive drills. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 65 (11), 2150-2159. (doi:10.1109/TUFFC.2018.2867535).

Abstract

Ultrasonic percussive drills are a leading technology for small rock drilling applications where power and weight-on-bit are at a premium. The concept uses ultrasonic vibrations to excite an oscillatory motion in a free-mass, which then delivers impulsive blows to a drilling-bit. This is a relatively complex dynamic problem involving the transducer, the free-mass, the drilling-bit and, to a certain extent, the rock surface itself. This paper examines the performance of a full-wavelength transducer compared to a half-wavelength system, which may be more attractive due to mass and dimensional drivers. To compare the two approaches, 3-D finite-element models of the ultrasonic percussive stacks using full and half-wavelength ultrasonic transducers are created to assess delivered impulse at similar power settings. In addition, impact-induced stress levels are evaluated to optimize the design of drill tools at a range of internal spring rates before, finally, experimental drilling is conducted. The results suggest that full-wavelength systems will yield much more effective impulse but, interestingly, their actual drilling performance was only marginally better than half-wavelength equivalents.

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Contributors

Author: Xuan Li

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