Since the internal fracture and cracking deformation of the rock is difficult to be observed directly, it is hard to effectively study the rock breaking process of the drill teeth in the indoor test. Therefore, the rock breaking process when the drilling teeth are pressed into the rock is observed by infrared thermal image nondestructive testing technology. According to the infrared characteristics of rock fragmentation, the size of the radius of different damage areas was quantitatively determined, and the temperature rise difference of different rock damage areas was explained in combination with the cavity expansion model (CEM) theory, and the temperature rise difference of different damage areas was caused by different thermal coupling mechanisms; the damage radius and temperature rise size of the rock showed that the degree of damage caused by the drill teeth to the rock was related to the geometry of the drill teeth; the damage caused by the spherical drill teeth on the rock surface was larger, and the temperature rise caused by the tapered drill teeth in the rock damage area was higher. The reliability of the method of dividing the radius of rock damage by infrared characteristics is verified by the volume of rock fragmentation, and it provides help to study the fracture and damage mechanism of rock in the process of rock crushing.

As conglomerate generally has the characteristics of complex pore structure and serious non-uniformity, the rock breaking efficiency of Polycrystalline Diamond Compact (PDC) bit drilling conglomerate stratum is generally low, and it is difficult to effectively study the PDC tooth rock breaking process in laboratory test. A numerical model of PDC teeth pressing into conglomerate is established by DEM, and the accuracy of the numerical model is verified by laboratory test. The fracture pattern and process of conglomerate under different impingement displacement, rake Angle and heterogeneity of conglomerate are studied. The results show that: The number of cracks in conglomerate increases with the increase of inputting displacement and heterogeneity within a certain range. Tensile crack is the main crack when gravel is pressed, shear crack is the main crack when matrix is pressed. With the increase of conglomerate heterogeneity, the maximum pressure will be increased and the distribution of conglomerate field will be wider, and the supporting effect of gravel in conglomerate will be enhanced.