Bit-rock interaction mechanisms and cracks propagation in rock cutting

Understanding the Polycrystalline Diamond Compact (PDC) bit-rock interaction is essential for optimizing bit design and enhancing drilling performance. This study develops an interaction model through linear cutting tests and derives an analytical solution based on the Mohr-Coulomb criterion to characterize crack initiation, propagation, and morphology. Experiments employing a self-developed cutting device and digital image correlation (DIC) show that rock undergoes brittle failure under cutting: the vertex of the crushed core first reaches the strength limit, followed by progressive fracture and eventual chip formation. Predicted failure surfaces, generated via a custom MATLAB program, agree with experimental crack paths within an error margin of ≤20%, validating the model. Further analysis indicates that both average cutting force and its dynamic fluctuation increase with cutting angle and depth, while cutting stability decreases. The model provides theoretical support for PDC bit design and drilling parameter optimization.