Combined finite-discrete element method for modeling the interaction between single PDC cutter and brittle rock

This paper describes a combined finite-discrete element method for simulating the interaction between single PDC cutter and brittle rock. The proposed method is capable of capturing the nucleation, propagation, branching, and coalescence of cracks as well as the contact between fragments during the cutting process. A detailed description of the method is provided. A linear Mohr-Coulomb criterion with tension cutoff is applied to identify which edge is failure based on the normal and shear stresses estimated from the triangular elements abutting from the edge. The Munjiza-NBS algorithm and Simple-Common-Plane (SCP) contact algorithm are used for the contact detection and interaction, respectively. The method is then validated against the theoretical results of Brazilian disc test and uniaxial compressive strength test. The results demonstrate that the proposed method is of high accuracy, especially before rock failure, because the cracks in the model are introduced on the fly by splitting the nodes where and when needed. Finally, several typical cases of the interaction between single PDC cutter and brittle rock are performed. The numerical results indicate that the wedging effect is significant, leading to the formation of large size chippings for brittle rock cutting.