Ultrasonic Cutting of Rock Materials

Abstract

Low-frequency reciprocatory-rotary motion is imparted to a conventional axially vibrated ultrasonic cutter (18 kHz) that is impregnated with diamond grit of average size 0.003 in. The rotary motion is in a plane normal to the cutter axis. Cutting rates in rock materials of 10 ft/h are exceeded for 1-in. diam circular holes drilled to depths greater than 1 ft. Peak axial amplitude was 1.6 mil and the rotary motion was less than three to-and-fro oscillations per minute. Specific energy of the cutting process was measured to be less than 100 J/cm3 or less than that involved in the rotary cutters used for oil well drilling. Pulsed excitation at a 50% duty cycle leads to an 8%–10% increase in drilling rate for the same power input. Self pumping of the abraded material is obtained through subharmonic vibration of the cutter on pulse excitation. Static pressure, peak amplitudes, and rotary motion are optimized.

Ultrasonic rock sampling using longitudinal–torsional vibrations

“…Research was reported where a low-frequency reciprocatory-rotary movement was imparted to an 18 kHz longitudinal ultrasonic cutter [6].…”