Rock Breaking Process and Efficiency Analysis of Conical Cutting Teeth under Rotary and Torsional Impact

In order to gain a better understanding of the rock-breaking process and efficiency of conical cutting teeth under rotary and torsional impact loads, numerical simulation and experimental data verification were conducted to study the rock’s internal stress changes, damage characteristics, breaking volume, depth and rock breaking specific work by the two methods at different impact amplitudes and frequencies. The numerical simulation and analysis results showed that both the rock-breaking processes of conical cutters under rotary impact and torsional impact could be divided into four stages: cutter intruding into rock, damage through crack initiation, damage through crack propagation, and rock cuttings avalanche. The tensile stress is the main reason for the cracks from the inside to the surface of rock, and the internal damage and micro-cracks appear mainly due to compressive shear stress. With the increase of impact amplitude and impact frequency, the broken volume of rock will increase in both the two ways. When the impact amplitude and frequency are increased to certain values, the increase of rock-breaking volume tends to be mild, and the maximum rock-breaking volume under rotary impact is higher than that under torsional impact. Among the three rock breaking methods - conventional cutting, rotary impact and torsional impact - the rock breaking specific work of conventional cutting is the greatest, and the rock breaking specific work under the conditions of different impact amplitudes and frequency of torsional impact is generally lower than that of rotary impact.