Research on the rock-breaking characteristics and laws of worn conical PDC cutter under penetration-cutting action

Conical polycrystalline diamond compact (PDC) cutters possess a unique 3D cutting structure and exhibit superior rock-breaking performance in hard formations through plowing. However, the rock-breaking characteristics and laws of worn conical PDC cutters remain poorly understood. In this study, a numerical model of worn conical PDC cutters under penetration-cutting conditions was established to analyze cutting force, penetration depth, temperature distribution and rock stress. The effects of wear height and weight on bit (WOB) on tangential force, penetration ability and MSE were systematically investigated. Results show that worn cutters present significant cutting force fluctuations in the penetration stage and break rock via edge shearing, forming discontinuous trapezoidal cross-section cutting grooves. With increasing wear height, cutter temperature decreases by 22% under 800 N WOB, temperature concentration shifts from the rear to front of the wear surface, and tangential force positively correlates with the cutter-rock tangential projection area. Within 0–1.0 mm wear height, tangential force rises, MSE declines and penetration ability improves; WOB increases tangential force and penetration depth with little impact on MSE. Severe blunting at 1.5 mm wear height leads to a sharp drop in rock-breaking efficiency. These findings provide theoretical guidance for the development of conical PDC bits and the extension of their service life.