Discrete element simulation of tribological interactions in rock cutting

• DEM is capable of reproducing the damage formation during calibration tests.
• Particle size is not a free parameter but influences the macro-properties.
• The correlation between numerical and theoretical models was not strong.
• Normal and cutting forces increase with an increase in depth of cut.
• DEM is capable of simulating rock cutting processes with different cutting tools.

Tool forces from rock cutting tests were numerically simulated by using a discrete element method (DEM). Tribological interactions such as contact, shearing, fracturing, friction and wear were used during these cutting tests. Particle assemblies, representing Paarl granite and Sandstone-2, were created in through a material-genesis procedure. The macro-properties of the particle assemblies, namely Young's modulus, Poisson's ratio, uniaxial and triaxial compressive strength, and Brazilian tensile strength, were calibrated. The influence of particle size on the calibration was also investigated.Different rock cutting tools were simulated, namely a chisel-shaped tool and a button-shaped tool. The numerical cutting tools were treated as rigid walls to simplify the simulation and the tool forces were therefore not influenced by wearing of the cutting tool. In each simulation the cutting tools advanced at a constant velocity. The tool forces, in three orthogonal directions, were recorded during the numerical simulations and the peak cutting forces were also predicted by theoretical equations. The damage to the assemblies, representing Paarl granite and Sandstone-2, was revealed as broken bonds, which merge into macroscopic fractures. The mean peak cutting forces obtained from numerical, theoretical and experimental models (from the literature) were compared. It was pointed out that the influence of cutting depth and wear plays a substantial part in the cutting process and has to be included in the numerical simulation for the results to be accurate and verifiable.