Efficiency of percussive drilling of rock with dissipative joints

摘要: Abstract The nonlinear dissipative spring mass (NDSM) model for a percussive drill rod joint of the coupling sleeve (CS) type has been implemented into Modula-2 program with aid which drilling rock is simulated. Transmission and dissipation energy are first studied when rectangular stress wave, generated through impact by uniform hammer, transmitted single joint. efficiency transmission increases from 81 to 94% relative decreases 8 1 or 2% length hammer varies relatively short long. effect preload weak in range medium high preload. process number joints but depends little on For soft rock, length, whereas hard dependence not monotonic. This because requires long incident wave efficient conversion work at bit, reverse true rock. It also found that may be considerably underestimated if effects each shape multiple reflections within string neglected.