Cutting attitude inclination angle and rock-breaking mode characteristics of disc cutter

The identification of rock-breaking mode is a key basis to improve cutting ability, and the cutter cutting attitude has a significant influence on rock-breaking mode. In this study, the internal relationship between cutting attitude and rock-breaking mode was explored, and the optimal cutting attitude parameters of low energy consumption and high efficiency rock-breaking were inferred. Based on the massive collapse state of the wedge surface acting rock when disc cutter vibrates axially upward, the rock tensile-shear coupling failure condition was given according to the Mohr-Coulomb criterion on the basis of the nonlinear rock failure criterion, and the three-segment linear rock failure global criterion (tensile failure, tensile-shear coupling failure, shear failure, compression-shear coupling failure and compression failure) was obtained. The mathematical description of the cutter wedge surface compressive stress under different rock-breaking modes was got. Based on the principle of minimum energy of the wedge surface action, the identification method of rock-breaking mode was proposed, and the load model of cutting rock with disc cutter of oblique attitude was constructed. The correlation between load characteristics of the cutter, rock-crushing characteristics (rock fragmentation distribution and dust size distribution) and rock-breaking mode under different cutting attitude inclination angles was analyzed by numerical simulation and experiment. The results show that the characterization values of wedge surface energy consumption of disc cutter are proportional to the attitude inclination angle, and rock-breaking mode changes from tensile-shear coupling failure to compressive-shear coupling failure. The characterization values of wedge surface energy consumption of disc cutter in vibration cutting are obviously less than that in non-vibration cutting, and it is mainly caused by tensile-shear coupling failure, while the tension-shear and compression-shear coupling failure exists approximately in equal proportion in non-vibration cutting. When the wedge surface component of axial velocity is greater than that of feed velocity, the friction is transformed into rock-breaking assistance, and the energy consumption of the wedge surface is significantly reduced. The macroscopic morphology of disc cutter breaking rock is like the large crescent shape, and the microscopic morphology of the rock powder is like polyhedron and spheroid. The attitude inclination angle of the cutter is inversely proportional to the amount of the rock fragments, and is proportional to the amount of the rock powder (spherical-like dust decreases and polyhedron-like dust increases). It indicates that as the attitude inclination angle increases, the extrusion effect of the cutter teeth edge is weakened, and the energy consumption of dust generated by the wedge surface extrusion increases, which is consistent with the influence of the cutting attitude on the energy consumption of the wedge surface during the identification process of rock-breaking mode. The radial load and the attitude inclination angles of disc cutter are concave, the theory and simulation are consistent with the experimental radial load law, and the average errors are 8.46% and 9.55%, respectively. The rationality of the identification method of disc cutter rock-breaking mode, the load model of cutting rock with inclined attitude and the numerical simulation is verified.