Obtaining Constitutive Relationship for Rate-Dependent Rock in SHPB Tests

Zhou, Zilong; Li, Xibing; Ye, Zhouyuan; Liu, Kewei

doi:10.1007/s00603-010-0096-3

Cited by 95 publications

(33 citation statements)

References 18 publications

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“…2a). It is quite similar to the experimental waveform without an apparent dispersion phenomenon (Li et al 2005;Zhou et al 2010). But from the protrusions of the incident signals and the obvious decrease in the amplitude of the transmitted wave compared with the incident wave, it can be inferred that there is a tensile wave propagating in a reverse direction and the incident wave does not transmit into the transmitted bar completely.…”

Section: Pfc Model Of the Shpb System With A Special Shape Strikersupporting

confidence: 71%

“…It is worth noting that the appearance of this platform in the reflected wave requires some preconditions. Zhou et al (2010) have discussed loading conditions for specimen deformation at a constant strain rate, concluding that, only when the loading stress and deformation stress in the specimen have the same changing pattern, can the specimen deform at a constant strain rate. From this point, it can be inferred that a constant strain rate in the specimen can be achieved under the half-sine loading wave generated by this special shape striker, which possesses a rising edge with a certain slope.…”

Section: Strain Rate Evolution Of the Specimenmentioning

confidence: 99%

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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: Pfc Model Of the Shpb System With A Special Shape Strikersupporting

confidence: 71%

Section: Strain Rate Evolution Of the Specimenmentioning

confidence: 99%

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

2013

Self Cite

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“…Unlike a conventional rectangular incident wave, the rising pulse shape should be shaped to mimic the constitutive behavior of the green sandstone specimen [18]. Therefore, to accurately achieve a constant strain rate, the incident wave should be shaped to have a nearly linear segment in the lower stress range and a curved segment in the higher stress range to mimic the stress-strain behavior of green sandstone [6]. According to the discussion above, it was crucial to study how to simply and effectively alter the rising portion of the wave to mimic the constitutive behavior of a green sandstone specimen, which is a requirement for a constant strain rate.…”

Section: Pendulum Hammer-driven Shpb Apparatusmentioning

confidence: 99%

“…However, in a common SHPB test, the incident pulse is a square waveform characterized by a short rising time, which is not ideal in rocks for approaching dynamic equilibrium and a constant strain rate. Usually, most results from SHPB tests are presented with an average strain rate, which is not proper for most rock materials, as they show strong strain rate effects [6]. A longer rising time in the incident wave pulse is an indispensable condition for achieving dynamic force equilibrium in rock samples before failure.…”

Section: Introductionmentioning

confidence: 99%

“…In consideration of the poor repeatability of the pulse shaper method and the advantages of the specially shaped striker method, such as reusability and increased test repeatability [6,34], the special shape striker method was selected as the first priority for further investigation. In this study, the goal was to produce constant strain rate incident waves by impacting the incident bar with a pendulum hammer with different geometric parameters at different impact velocities.…”

Section: Introductionmentioning

confidence: 99%

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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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Fracturing behaviors of flawed granite induced by dynamic loadings: A study based on DIP and PFC

Wang,

Sun,

et al. 2024

Deep Underground Science and Engineering

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This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split‐Hopkinson pressure bar testing, focusing on factors like grain size and flaw dimensions. By means of digital image processing and the discrete element method, Particle Flow Code 2D (PFC2D) models were constructed based on real granite samples, effectively overcoming the limitations of prior studies that mainly relied on randomized parameters. The results illustrate that the crack distribution of granite is significantly influenced by grain size and flaw dimensions. Tension cracks predominate and mineral boundaries, such as between feldspar and quartz, become primary crack sites. Both flaw length and width critically affect the crack density, distribution, and dynamic strength of granite. Specifically, dynamic strength tends to decrease with the enlargement of flaws and increase with an increase in flaw angles up to 90°.

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Obtaining Constitutive Relationship for Rate-Dependent Rock in SHPB Tests

Cited by 95 publications

References 18 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

Fracturing behaviors of flawed granite induced by dynamic loadings: A study based on DIP and PFC

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