Numerical Simulation Study on the Rock Breaking Effect of Multiple Axe-Shaped Cutters in Rotary Percussion Drilling

The compatibility of percussion tools， PDC cutter types and hard rock formations is a key factor in extending the service life of percussion tools and drill bits and achieve the best rock breaking effect， but it has been rarely studied. In this paper， considering the interaction between the axial static load and the impact load， cutters and formation during rotary percussion drilling， a numerical model of single and double axe-shaped cutter three-dimensional rock breaking under conventional drilling and rotary percussion drilling modes was established. The multi-cutter rock breaking effects under different drilling modes were compared， the distribution of tensile， compressive and shear stresses in the rock which is broken by single and double cutters under impact load was analyzed， and the mechanism of multi-cutter rock breaking under impact load was revealed. The penetration depth of the cutters， the rock damage under the cutting surface and the variation of the force of the cutters under different cutter rake angles and double cutter spacing were studied. The results show that there is obvious interference of shear stress and tensile stress in the double-cutter rock breaking process. As the front rake angle of the cutters increases， the rock section damage area， penetration depth and tangential force of the cutters gradually decrease， and the best front rake angle is 20°. Given the front rake angle， increasing the cutter spacing will lead to the gradual weakening of the interference between two cutters， and the residual rock ridge will become more significant. Considering the rock cutting effect and the force of the cutters， the double axe-shaped cutters spaced at 16 mm can achieve a high rock breaking efficiency and service life. The research results provide theoretical and engineering references for the selection of PDC bit type and the layout of cutters in the process of percussion drilling.