Rake angle optimization for balanced efficiency and durability in PDC cutter cutting granite interaction via infrared thermal dynamics and fragmentation mechanism.

In deep drilling operations, the interaction mechanism between the Polycrystalline Diamond Compact (PDC) cutter and the granite directly affects the granite breaking efficiency and the service life of the cutter. To reveal the correlation between the infrared radiation characteristics and the granite mechanics failure behavior during the single-tooth cutting process, the study utilized a modified shaper testing machine and a high-precision infrared thermal imager (with a measurement accuracy of ± 0.01 °C and a spatial resolution of 0.6mrad) to monitor the dynamic contact process between PDC cutter and granite under the condition of 15° ~ 30° rake angles. The results show that the infrared temperature undergoes a significant increase at the moment of contact, and as the rake angle increases from 15° to 30°, the peak initial contact temperature rises from 26.30 °C to 91.46 °C, indicating that an escalation of the rake angle intensifies the degree of granite fragmentation but leads to an upward shift in the temperature fluctuation range at the contact interface, posing a potential threat to the durability of the PDC cutter. Infrared imaging analysis reveals that the granite fragmentation pattern exhibits the characteristics of diffusing from the local contact center to the circumferential direction, following a three-stage evolution law of energy accumulation, mixed failure, and unloading. By comparing the simultaneously collected cutting force data, it is found that the fluctuation of infrared radiation temperature is strongly correlated with the rock compaction-fracture cycle process, and the peak-valley changes in temperature highly coincide with the reciprocating characteristics of the cutting force waveband, verifying the feasibility of infrared thermal signals as real-time indicators of rock failure status. With the raise of the rake angle, the infrared characteristic temperature tends to decrease (mean is 39.54 at 30°, a decrease of 32% compared to 15°), while the variance significantly increases (variance is 21.34 at 30°, an increase of 48%), reflecting intensified energy dissipation but improved fragmentation stability during the granite breaking process. Comprehensive analysis of the Specific Energy of Rock Fragmentation (SERF) and cutting force reveals that when the rake angle exceeds 25°, the intensity of infrared radiation response, and cutting force increase simultaneously. Based on the principle of collaborative optimization of efficiency and service life, it is recommended to control the rake angle within the range of 15° ~ 25° to balance the granite breaking efficiency and cutter wear characteristics. This paper reveals the damage evolution law of granite to some extent.