Full and Half-Wavelength Ultrasonic Percussive Drills

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.

Ultrasonically assisted coring of rocks

“…The horn has a stepped geometry to boost the generated amplitude from the piezoceramic rings stack, and it also has a two-start auger to extract the spoils. Two tungsten carbide teeth were silver brazed into the front slots of the horn [4], but this is known to be a difficult technique with Titanium [12], and tooth failure could potentially be noted as a consequence.…”

“…This technique uses a Langevin-style ultrasonic transducer to excite a percussive stack which consists of a free mass and a free drilling bit, such that percussive pulses can be transmitted through the series chaotic impact between the transducer, free mass and drill bit and then into the rock [3]. The dynamic optimization of the stack is a complex problem [4], and in order to reach a significant depth, technical issues surrounding spoil augering or alternative extraction will still need to be addressed.…”

Passive Versus Active Control of Weight-on-Bit for an Ultrasonic Percussive Drill

“…Harkness et al used only the downward pressure of the crimped pipe to provide WOB to the device in their study of a crimped ultrasonic drilling and coring device [27]. Li et al used horizontally suspended weights to provide WOB when comparing the performance of full-wavelength and half-wavelength ultrasonic drill [28]; a linear actuator was used to provide WOB in ultrasonic-assisted drilling with active control [29]. Bai et al used horizontally suspended weights to provide drilling force for ultrasonic drill [30].…”

Dynamic response of high-power ultrasonic system based on finite element modeling of piezoelectric

“…Several studies have been implemented to evaluate the system response when adding different components to the transducer. Xuan Li et al [11] have modified the ultrasonic vibration device for rock drilling systems that require a small size but very high working performance. Based on the design of the existing Langevin transducer, Mathieson Andrew succeeded in modifying the design parameters to create an ultrasound device suitable for use in bone surgery [2].…”

“…(11) www.engineeringscience.rs publishing Viet Dung Luong et al -Dynamic response of highpower ultrasonic system based on finite element modeling of piezoelectric [ ] [ ][ ] ijkl D is a fourth-order elastic tensor of the elastic stiffness parameter evaluated at a constant electric field [ ]…”