Effects of microstructures on dynamic compression of Barre granite

Xia, Kaiwen; Nasseri, M. H. B.; Mohanty, B.; Lu, Fangyun; Chen, R.; Luo, S. N.

doi:10.1016/j.ijrmms.2007.09.013

Cited by 220 publications

(75 citation statements)

References 15 publications

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“…In addition, it can be seen from the graph that the peak stress time of the specimen corresponds to the turning point of the reflected wave, implying that the qualitative change of the macroscopic elastic properties caused by the quantitative accumulation of internal damage is co-instantaneous as the bearing capacity of the specimen reaches its limit. Xia et al (2008) conducted a uniaxial compressive test on Barre granite under a high strain rate and obtained reflected waves which are similar to that in Fig. 9b.…”

Section: Strain Rate Evolution Of the Specimenmentioning

confidence: 64%

Numerical Simulation of the Rock SHPB Test with a Special Shape Striker Based on the Discrete Element Method

2013

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A split Hopkinson pressure bar (SHPB) system with a special shape striker has been suggested as the test method by the International Society for Rock Mechanics (ISRM) to determine the dynamic characteristics of rock materials. In order to further verify this testing technique and microscopically reveal the dynamic responses of specimens in SHPB tests, a numerical SHPB test system was established based on particle flow code (PFC). Numerical dynamic tests under different impact velocities were conducted. Investigation of the stresses at the ends of a specimen showed that the specimen could reach stress equilibrium after several wave reverberations, and this balance could be maintained well for a certain time period after the peak stress. In addition, analyses of the reflected waves showed that there was a clear relationship between the variation of the reflected wave and the stress equilibrium state in the specimen, and the turning point of the reflected wave corresponded well with the peak stress in the specimen. Furthermore, the reflected waves can be classified into three types according to their patterns. Under certain impact velocities, the specimen deforms at a constant strain rate during the whole loading process. Finally, the influence of the micro-strength ratio (s c =r c ) and distribution pattern on the dynamic increase factor (DIF) of the strength DIF were studied, and the lateral inertia confinement and heterogeneity were found to be two important factors causing the strain rate effect for rock materials.Keywords SHPB Á Special shape striker Á Discrete element method Á Strain rate effect Micro-strength ratio (ratio of contact-bond shear to normal strength) n Time-step N Current time-step DTðnÞ Interval time under time-step n(s) l Frictional coefficient at the specimen/bar interface

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Section: Strain Rate Evolution Of the Specimenmentioning

confidence: 64%

Numerical Simulation of the Rock SHPB Test with a Special Shape Striker Based on the Discrete Element Method

2013

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“…Furthermore, Vecchio and Jiang [14] have reported that, in SHPB tests conducted on high-work-hardening materials, high-strength, high-work-hardening rate (HSHWHR) materials are more conducive than soft materials for shaping an incident pulse for a constant strain rate. Xia et al [15] have obtained constant strain rate conditions during dynamic loading by applying pulse shaper technique in Barre granite studies. In tests of low impedance specimens, such as POM and PP plastics, Lee et al [16] have used a pulse shaper to increase the incident wave rise time.…”

Section: Introductionmentioning

confidence: 99%

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Zhu

Niu

et al. 2017

Shock and Vibration

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During the Split-Hopkinson pressure bar (SHPB) tests driven by pendulum hammer, employing a proper special shape striker is an effective way to obtain dynamic stress equilibrium condition and to get constant strain rate of the rock specimen. To find the proper special shape striker, a striker with a cambered surface was introduced and eight geometrically different hammers were designed to analyze the effect of hammer geometry on the waveform of excited incident stress waves. Based on experiments and simulations, parameter effects, including the cambered hammer curvature radius and hammer diameter, length, and impact velocity, on the incident wave shape were examined. These parametric studies provided guidelines for achieving constant strain rates in rock specimens during SHPB tests. The use of different diameter hammers was noted for shaping stress-time curves to follow the stress-strain behavior of green sandstone. Finally, to examine the applicability of using hammer geometry for shaping incident waves to achieve constant strain rate, SHPB tests on green sandstone specimens were conducted. The results demonstrated that a constant strain rate (100 s −1 ) lasting for 70 s was achieved with the 8# hammer (3.7 kg; curvature radius, diameter, and length of 100, 70, and 126.3 mm, resp.). In addition, dynamic experiments on green sandstone were carried out under various strain rates and the results showed that the initial tangential modulus was almost unaffected by strain rate. The strain at peak stress tended to increase with rising strain rate and the dynamic strength of green sandstone showed an apparent rate dependency.

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“…However, as pointed out by XIA et al, (2008), the effect of micro-structures on the dynamic behaviours of Barre granite was inconclusive due to lack of control of the loading rate and other deficiencies in the experimental design. It is thus necessary to revisit the tension tests on Barre granite in a systematic manner with newly developed techniques on SHPB tests.…”

Section: Introductionmentioning

confidence: 99%

Loading Rate Dependence of Tensile Strength Anisotropy of Barre Granite

Dai

Xia

2010

Pure Appl. Geophys.

115

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Granitic rocks usually exhibit strongly anisotropy due to pre-existing microcracks induced by long-term geological loadings. The understanding of the rock anisotropy in mechanical properties is critical to a variety of rock engineering applications. In this paper, Brazilian tests are conducted statically with a material testing machine and dynamically with a split Hopkinson pressure bar system to measure both static and dynamic tensile strength of Barre granite. To understand the anisotropy in tensile strength, samples are cored and labelled using the three principle directions of Barre granite to form six sample groups. For dynamic tests, a pulse shaping technique is used to achieve dynamic equilibrium in the samples during the dynamic test. The finite element method is then implemented to formulate equations that relate the failure load to the material tensile strength by employing an orthotropic elastic material model. For samples in the same orientation group, the tensile strength shows clear loading rate dependence. The tensile strengths also exhibit clear anisotropy under static loading while the anisotropy diminishes as the loading rate increases, which may be due to the interaction of pre-existing microcracks.

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Effects of microstructures on dynamic compression of Barre granite

Cited by 220 publications

References 15 publications

Numerical Simulation of the Rock SHPB Test with a Special Shape Striker Based on the Discrete Element Method

Numerical Simulation of the Rock SHPB Test with a Special Shape Striker Based on the Discrete Element Method

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Loading Rate Dependence of Tensile Strength Anisotropy of Barre Granite

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