Study On Dynamic Fracture Capabilities Of Rock Materials And Numerical Simulation

The tensile strength of rock material is far less than its compressive strength, it’s damage caused mainly by the tension, and often associated with the loading rate. With engineering blasting widely applied in rock and minerals exploiting, underground caverns construction and flat excavation, the study on rock dynamic mechanical properties has achieved a great development. Under the background of coal mining in Huainan-Huaibei areas and with the rock materials from Huainan Pansan Coal Mine processed into Brazil disks of different specifications, the dynamic mechanical properties of SHPB apparatus under different speed are tested in this paper and with the help of software ANSYS/LS-DYNA, the effect of pulse shape on wave form is analyzed. Main contents include:1) The theoretical foundation, basic principle of test and two important hypotheses as well as testing designs are discussed. The SHPB test design is presented. The diffusion of stress wave in SHPB is analyzed by one-dimensional stress wave theory. The data process formula of the three-wave method and the two-wave method is deduced.2) The experiment studied the rock dynamic tensile properties under high strain rates, broken pattern and broken order of the specimen are analyzed, and the effect of geometry size on broken time and strain rate are discussed. The effect of strain rate on tensile strength of rock and dynamic constitutive relation curve are obtained.The diffusion of stress wave in SHPB is analyzed by one-dimensional stress wave theory. The data process formula of the three-wave method and the two-wave method is deduced. The HJC constitutive model parameters are confirmed in the test by selecting rock materials.3) Specimens that are not broken from the centre but from the ends of load diameter to the center. The reasonable explanation is obtained by theoretical analysis. On the emission energy absorbed by the sample, and transmission are analyzed and the relationship of the incident energy, and obtain some changes under the impact of different energy velocity.4) Theoretical and numerical simulation analysis and proper explanations are made on those specimens. The HJC constitutive model parameters are confirmed in the test by selecting rock materials, and verified the effectiveness and test results of the test.5) Extends the simulation test devices, and wave form dispersion on the rod diameter SHPB devices are discussed. Discussed on split test through numerical simulation, the effect of loading wave of rectangle and half sine wave on wave dispersion is analyzed and wave dispersion of the elements from the same and different stem diameters. On the basis of the effect of geometric size of pulse shaper and specimen size on the test results, strain rate effect of dynamic tensile strength is obtained, and rock stress-strain curve is reconstructed.