Thermo-mechanical coupling in cracked granite: Influence of crack inclination on fracture behavior and temperature evolution

Crack inclination angle ( α ) plays a critical role in the dynamic failure and thermo-mechanical coupling of granite, which is vital for rockburst monitoring and prevention. In this study, granite specimens with various prefabricated crack inclinations ( α = 0°, 30°, 60°, 90°) were tested using a split Hopkinson pressure bar (SHPB) system. Transient crack tip temperatures were monitored in real time by high-speed infrared thermography, and crack propagation was analyzed using digital image correlation (DIC). The main findings are summarized as follows: 1) Propagation mode and mechanical properties: Increasing crack inclination causes a transition from pure tensile propagation to tension–shear mixed modes. At α = 60°, enhanced shear promotes branching cracks, while at α = 90°, crack closure suppresses propagation and induces localized damage. 2) Strength characteristics: Peak stress exhibits a “U-shaped” trend with respect to α , reaching the lowest value at α = 60°. 3) Thermal response: Crack tip temperature rise is strongly dependent on inclination. The maximum rise (up to 9.266 °C) occurs at α = 30° and 60° due to pronounced tension-shear coupling and frictional slip, whereas α = 0° and 90° show smaller increases. 4) Two-stage temperature evolution: Before peak stress, ∼80% of the temperature rise originates from plastic work; after peak stress, crack slip and friction dominate, leading to accelerated heating. 5) Crack tip temperature rise serves as a sensitive indicator of local energy concentration and disaster risk, providing theoretical support for monitoring and prevention strategies in deep mining. • A high-speed infrared system is used to monitor transient crack tip temperature in dynamic rock fracture. • Crack propagation evolves from pure tensile to tension-shear mixed mode as α increases. • Crack tip temperature and thermo-mechanical coupling vary significantly with different crack inclinations. • Crack tip temperature evolution exhibits plastic-to-friction dominated two-stage mechanism.