Numerical and experimental investigations on the rock-cutting mechanism of cylindrical PDC cutters and the influence of key parameters on cutting efficiency

Polycrystalline diamond compact (PDC) bits often encounter challenges such as stick–slip, cutter breakage, and low rate of penetration (ROP) when drilling through complex formations with interlayered soft and hard rocks. Cylindrical PDC cutters have demonstrated promising rock-cutting performance in hard formations, offering a new approach for drilling hard and brittle strata. However, the underlying mechanical mechanisms still need to be thoroughly elucidated. In this study, the rock-breaking mechanism of a single cylindrical PDC cutter is systematically investigated by combining theoretical analysis, finite element (FE) simulation, and laboratory experiments. First, a theoretical model for the cutting force is derived based on Evans’ cutting theory, clarifying its mechanical essence. Subsequently, an elastoplastic damage FE model based on the Drucker-Prager criterion is established. This model quantitatively analyzes the effects of the cutter back rake angle (5°-25°) and the rock static elastic modulus (10GPa-50GPa) on the von Mises equivalent stress, equivalent plastic strain (PEEQ), and mechanical specific energy (MSE) during the rock fragmentation process. The results show that the Mises stress increases logarithmically with the increase of the post-cutting angle and the elastic modulus, while the PEEQ strain shows an exponential decreasing trend. The MSE increases with both the back rake angle and elastic modulus; the rock-breaking efficiency is highest at a 5° back rake angle and lowest at 25°. The reliability of the simulation results is confirmed through cross-validation between micro-PDC bit laboratory experiments and numerical simulations. Based on the quantitative results, a small back rake angle of 5° is recommended for hard rocks (elastic modulus > 30GPa) to reduce energy consumption, while a 10°-15° back rake angle is suggested for soft to medium-hard formations to balance efficiency with chip removal. This study provides specific quantitative evidence and practical engineering guidance for the optimal design of PDC bits in heterogeneous formations.