Thermal Analysis and Thermal–Mechanical Stress Simulation of Polycrystalline Diamond Compact Bits During Rock Breaking Process

Polycrystalline diamond compact (PDC) bits are widely used in oil, gas, and geological exploration. During rock breaking, most of the work is converted into cutting heat, leading to a rise in cutter temperature and potential damage. However, the influence of formation temperature and rock properties on cutting temperature and thermal stress remains insufficiently understood. This study combined numerical simulation and experimental methods to investigate the temperature rise and thermal stress of a single PDC cutter during rock breaking, focusing on the effects of formation temperature (27–250 °C) and rock strength (sandstone, marble, and granite). The results show that the temperature rise of the PDC cutter adheres to the following three distinct stages: rapid increase, slow increase, and stabilization. Rock strength significantly affects the temperature rise rate and stress; when breaking granite, the cutter temperature reached approximately 131.4 °C, about 2–3 times higher than for marble and sandstone, while the rate of penetration (ROP) decreased by 70.6–75.6%. As formation temperature increased from 27 °C to 250 °C, the internal temperature difference within the cutter decreased from 72.6 °C to 35.6 °C, and the equivalent stress first increased and then decreased, peaking at 2.84 GPa at 50 °C. The ROP initially increased and then decreased with an increase in formation temperature. Numerical simulations and experimental findings are in good agreement. This study provides theoretical and technical guidance for optimizing cutter design and improving the rock-breaking efficiency and service life of PDC bits in deep and high-temperature formations.