Determination of Dynamic Compressive and Tensile Behavior of Rocks from Numerical Tests of Split Hopkinson Pressure and Tension Bars

FEM-based numerical testing systems of the split Hopkinson pressure bar (SHPB) and the split Hopkinson tensile bar (SHTB) are established to study the characteristics of rock materials under dynamic compressive and tensile loadings. First of all, the accuracy and applicability of the numerical testing system are validated and calibrated through comparison between the laboratory measurements and the simulation results. Subsequently, the dynamic behavior of rock is analyzed in detail with the numerical testing system followed by the underlying physical mechanism. For the SHPB tests, the simulation results demonstrate that the incident waveform is determined by the striker length, the striker shape and the pulse shaper. The dynamic increase factor (DIF) of the rock specimen varies with different impact velocities, which is attributed to the strain rate effect. The rock specimen size and bar size also have effects on the DIF. In addition, the interfacial friction between the rock specimen and the bars cannot be ignored. For the SHTB tests, it is found that the incident waveform is dependent on the striker tube length and the striker tube thickness. In addition, similar to the SHPB tests, the impact velocity, rock specimen size and bar size all have strong effects on the rock dynamic tensile strength.