Study On Mechanical Properties And Failure Morphology Of Granite Under Impact

In this paper,the ?50mm split Hopkinson pressure bar with equal section is used to study the dynamic mechanical properties of the granite,and the dynamic mechanical properties of the granite are simulated with the numerical software ANSYS/LS-DYNA.The laboratory experiment and numerical simulation are combined.Main research contents and results:(1)In order to use SHPB device to obtain more reliable dynamic parameters of brittle materials and low-impedance materials at medium and high strain rates,the existing devices have been improved.After repeated experiments,a circular copper piece with a diameter of 18 mm and a thickness of 1 mm was used as a waveform shaper.It can be seen that the pulse shaper modifies the stress wave from the original square wave with high frequency oscillations to a half sine wave with a smoother upslope and a smoother waveform.The effect of eliminating the high frequency signal and delaying the incident pulse is obvious,especially the reflected wave becomes The smoothness shows that the strain rate is relatively constant;(2)Under the SHPB uniaxial impact compression test,seven kinds of impact tests of different loading pressures were performed on the granite specimens.The results showed that the rock specimens were tested under low strain rate conditions.The pieces show integral integrity and gradually spall outwardly in the radial direction.At a higher strain rate,the sample shows a granular crushing failure mode;(3)The energy dissipation analysis in the SHPB impact test shows that the rock breaks and absorbs.Can increase linearly with the incident energy,When the loading waveform and the material of the sample are constant,the ratio of the energy absorbed by the rock to the incident energy is constant and is almost unaffected by the size of the sample.Under the condition of neglecting the kinetic energy of rock fragments,the energy density of rock crushing increases linearly with the increase of incident energy,and its growth rate decreases with the increase of sample size;(4)Based on numerical software ANSYS/LS-DYNA simulates the crushing process under a loading pressure of 0.15 MPa to investigate the failure phenomena of the granite specimens,and analyzes the stress-strain curves at different loading rates,which is generally consistent with the experimental results.