Experimental and Numerical Evaluation of Rock Dynamic Test with Split-Hopkinson Pressure Bar

Abstract

Feasibility of rock dynamic properties by split-Hopkinson pressure bar (SHPB) was experimentally and numerically evaluated with ANSYS/LS-DYNA. The effects of different diameters, different loading rates, and different propagation distances on wave dispersion of input bars in SHPB with rectangle and half-sine wave loadings were analyzed. The results show that the dispersion effect on the diameter of input bar, loading rate, and propagation distance under half-sine waveform loading is ignorable compared with the rectangle wave loading. Moreover, the degrees of stress uniformity under rectangle and half-sine input wave loadings are compared in SHPB tests, and the time required for stress uniformity is calculated under different above-mentioned loadings. It is confirmed that the stress uniformity can be realized more easily using the half-sine pulse loading compared to the rectangle pulse loading, and this has significant advantages in the dynamic test of rock-like materials. Finally, the Holmquist-Johnson-Concrete constitutive model is introduced to simulate the failure mechanism and failure and fragmentation characteristics of rock under different strain rates. And the numerical results agree with that obtained from the experiment, which confirms the effectiveness of the model and the method.

Influence of Disc Specimen Configuration on Its Three-Dimensional Dynamic Stress Balance

“…Disc Specimens. The stress balance factor, the dimensionless stress difference at both ends of the specimen, has been defined and widely used [29,33,[45][46][47]. It quantifies the stress balance of the specimen during dynamic impact.…”

A Study on the Split Hopkinson Bar Testing in Cold Environments

“…An observed signal at that point will indicate there is probably some reflection from the bearings supporting the bars. However Kang et al (2017) found that this problem is difficult to isolate and quantify as there may be other sources of waves. Alignment of the mounting brackets is performed by pointing a laser down the center of the launch tube.…”

“…The constant strain rate is mainly dependent on the rise of the incident pulse which can induce premature failure long before dynamic stress equilibrium could ever be reached in the sample. As a rule of thumb, the loading stress wave needs approximately 3 to 4 rounds to travel within the specimen for the stress to achieve an equilibrium (Kang et al, 2017). For the split Hopkinson bar to obtain accurate measurements, the dynamic loading must be slow enough so that the specimen is experiencing an essentially quasi-static load.…”

Experimental Study of the Rock Mechanism under Coupled High Temperatures and Dynamic Loads

“…Mahanta et al studied the effects of strain rate on fracture toughness and energy release rate of gas shales [33]. Peng used the split-Hopkinson pressure bar to conduct the Brazilian disc test and concluded that the time required to achieve a uniform stress state in specimen for the half-sine incident pulse is noticeably shorter than that for the perfectly rectangular incident pulse [37]. us, the influence of temperature on rock mechanical properties has been widely studied worldwide.…”