Suggested Methods for Determining the Dynamic Strength Parameters and Mode-I Fracture Toughness of Rock Materials

Zhou, Yingxin; Xia, Kaiwen; Li, X. B.; Li, H. B.; W., G.; Zhao, Jingshuo; Zhou, Zilong; Dai, Feng

doi:10.1007/978-3-319-07713-0_3

Cited by 80 publications

(65 citation statements)

References 9 publications

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“…As shown in Figure 2, in order to eliminate wave oscillation and reduce wave dispersion effects, the half-sine incident stress wave generated with a spindle-shaped striker has been suggested as the ideal loading waveform for SHPB device [20]. Before the dynamic tests, the coal-rock combined body specimen was sandwiched between the incident bar and the transmitted bar, and the stress wave transfer is made from the rock sample to the coal sample in the combined body specimen to simulate the actual stressed state of coal-rock strata under impact loading.…”

Section: Test Equipment and Testing Methodologymentioning

confidence: 99%

The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal‐Rock Combined Body

Gong

Hao

Luo

2018

Shock and Vibration

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In order to investigate the high loading rate effect on the behaviour and mechanical properties of coal-rock combined body, the dynamic compressive tests were conducted by using the Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×10 5 MPa/s to 4.0×10 5 MPa/s. The stress-strain curves, dynamic peak stress and strain, elastic modulus, and energy distribution law of coal-rock combined body under different loading rates were analyzed and discussed. The results show that the dynamic stress-strain curves of coal-rock combined body have a double-peak feature under high loading rate range, which can be divided into the initial bearing stage, the bearing decline stage, the bearing enhance stage, and the unstable stage. The first peak stress of the coal-rock combined body is independent of the loading rate, while the dynamic compressive strength (the second peak stress) and dynamic peak strain (the second peak strain) have a strong loading rate effect and will generally increase linearly with the loading rate. The first and second elastic moduli of coal-rock combined body are not sensitive to the loading rate. With the increase of the loading rate, the incident energy and reflective energy of coal-rock combined body increase rapidly, while the change of transmitted energy is very small. The absorption energy ratio of the coal-rock combined body shows a good linear law with the incident energy under different loading rates.

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Section: Test Equipment and Testing Methodologymentioning

confidence: 99%

The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal‐Rock Combined Body

Gong

Hao

Luo

2018

Shock and Vibration

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“…The grain size of the green sandstone varies from 200 to 500 m. The physical-mechanical parameters of green sandstone samples are shown in Table 1. In the SHPB tests, rock specimens were prepared according to previously suggested test methods of the International Society for Rock Mechanics [36]. The diameter and thickness of green sandstone specimens were 28 and 15 mm, respectively.…”

Section: Qualitative Stress-strain Relationship Of Green Sandstonementioning

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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“…It was experimentally noticed that crack extension occurred in mode I rather than shear mode or mixed mode. Many investigations were typically focused in opening mode failure for crack growth (Alfano et al, 2009;Erdogan & Sih, 1963;Fowell et al, 1995;Lim et al, 1994;Yoshihara & Kawamura, 2006;Zhang, 2002;Zhou et al, 2012). The cracks in brittle materials are often vulnerable to compressive loading rather than tensile loading (Ke et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Numerical evaluation of mode I/II SIF of quasi-brittle materials using cracked semi-circular bend specimen

Fayed¹

2018

10.5267/j.esm

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An in-house finite element code was utilized to evaluate mode I/II stress intensity factor (SIF) of an edge cracked semi-circular disc subjected to three-point bending. The specimen was considered as an isotropic and homogeneous material. Relative span length ratios of 0.3 to 0.8 in steps of 0.1 were invoked. Relative crack length ratios of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 were analyzed with crack angles up to 60° in steps of 5°. At the same crack length, mode I SIF decreases with increasing crack angle or decreasing the span length. The range of pure mode II decreases with increasing the span length. For the same crack length, the crack angle corresponding to the transition from a mixed mode I/II to a pure mode II increases with increasing the relative span length ratio. On the contrary, that angle decreases with increasing the crack length for the same span length. Good agreement has been generally obtained with relevant results found in the literature.

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Suggested Methods for Determining the Dynamic Strength Parameters and Mode-I Fracture Toughness of Rock Materials

Cited by 80 publications

References 9 publications

The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal‐Rock Combined Body

The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal‐Rock Combined Body

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

Numerical evaluation of mode I/II SIF of quasi-brittle materials using cracked semi-circular bend specimen

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