A numerical estimate method of dynamic fracture initiation toughness of rock under high temperature

With the limitations of measuring techniques, limited investigation on dynamic fracture testing of rocks at high temperature is reported. In this paper, an effective measuring method of the dynamic mode I fracture toughness of high-temperature rocks, combined with laboratory tests with the Discrete Element Method (DEM), is proposed. Based on the laboratory experiments conducted, including uniaxial compressive tests under different temperature conditions, the Brazilian test and split Hopkinson pressure bar (SHPB) test, the micro-parameters of the numerical model are calibrated and the validity of the numerical model of specimens and the simulated dynamic load tests are examined. The results show that the DEM can truly reflect the mechanical properties of rocks at high temperatures, and the simulation test can capture the dynamic fracture parameters of rocks at elevated temperatures. The test data indicates that the fracture initiation toughness of specimens increases linearly with the loading rate, while the fracture initiation time detected by the measurement circle near the notch tip decreases. When the loading rate is higher than 130 GPa m(1/2)/s, the fracture initiation toughness has a significantly negative relationship with the temperature within the temperature range of 25-400 degrees C.