Crack evolution law and failure mode of red sandstone under fatigue–creep interaction

2021 ◽  
Author(s):  
Ju Wang ◽  
Jiangteng Li ◽  
Zhanming Shi
Keyword(s):  
Failure Mode ◽  
Crack Evolution ◽  
Evolution Law ◽  
Red Sandstone

scholarly journals Research on crack evolution law and macroscopic failure mode of joint Phyllite under uniaxial compression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiangbo Xu ◽  
Dongyang Fei ◽  
Yanglin Yu ◽  
Yilun Cui ◽  
Changgen Yan ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Stress Level ◽  
Joint Effect ◽  
Crack Evolution ◽  
Evolution Law ◽  
Joint Inclination ◽  
Original Crack

AbstractIn order to explore the fracture mechanism of jointed Phyllite, the TAJW-2000 rock mechanics test system is used to carry out uniaxial compression tests on different joint inclination Phyllites. The influence of joint inclination of Phyllite failure mode is discussed, and the progressive failure process of Phyllite is studied. The test results show that the uniaxial compressive strength anisotropy of jointed Phyllite is remarkable. As the inclination increases, it exhibits a U-shaped change; When 30° ≤ α ≤ 75°, the tensile and shear failures along the joint inclination mainly occurs. the joint inclination controls the failure surface form of the Phyllite; The crack initial stress level of the joint Phyllite is 0.30–0.59σf, the crack failure stress level is 0.44–0.86σf. When α = 90°, the σcd value is the largest, and σcd with α = 90° can be used as the maximum reliable value of uniaxial compressive strength of Phyllite. Using the theory of fracture mechanics, it is analyzed that under uniaxial compression of the rock, the crack does not break along the original crack direction, but extends along the direction at a certain angle to the original crack. The joint effect coefficient is proposed to show the influence of the joint inclination on the uniaxial compressive strength of the phyllite. Both the test and simulation results show that when the joint inclination is 60°, the joint effect coefficient is the largest. The compressive strength is the smallest. Numerical simulation analyses the crack evolution law of phyllite under different joint inclination under uniaxial compression, which verifies that there are different failure modes of joint phyllite under uniaxial compression.

scholarly journals Research on the Pore Evolution of Sandstone in Cold Regions under Freeze-Thaw Weathering Cycles Based on NMR

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zheng Pan ◽  
Keping Zhou ◽  
Rugao Gao ◽  
Zhen Jiang ◽  
Chun Yang ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Pore Structure ◽  
Western China ◽  
Cold Regions ◽  
Abrupt Decrease ◽  
Evolution Law ◽  
Red Sandstone ◽  
Freeze Thaw ◽  
Evolution Characteristics ◽  
Pore Evolution

The evolution of the rock pore structure is an important factor influencing rock mechanical properties in cold regions. To study the mesoscopic evolution law of the rock pore structure under freeze-thaw weathering cycles, a freeze-thaw weathering cycle experiment was performed on red sandstone from the cold region of western China with temperatures ranging from -20°C to +20°C. The porosity, T2 spectral distribution, and magnetic resonance imaging (MRI) characteristics of the red sandstone after 0, 20, 40, 60, 80, 100, and 120 freeze-thaw weathering cycles were measured by the nondestructive detection technique nuclear magnetic resonance (NMR). The results show that the porosity of sandstone decreases first and then increases with the increase of the freeze-thaw weathering cycles and reaches the minimum at 60 of freeze-thaw weathering cycles. The evolution characteristics of porosity can be divided into three stages, namely, the abrupt decrease in porosity, the slow decrease in porosity, and the steady increase in porosity. The evolution characteristics of the T2 spectrum distribution, movable fluid porosity (MFP), and MRI images in response to the freeze-thaw weathering process are positively correlated with the porosity. Analysis of the experimental data reveals that the decrease in the porosity of the red sandstone is mainly governed by mesopores, which is related to the water swelling phenomenon of montmorillonite. Hence, the pore connectivity decreases. As the number of freeze-thaw cycles increases, the effect of the hydrophysical reaction on the porosity gradually disappears, and the frost heaving effect caused by the water-ice phase transition gradually dominates the pore evolution law of red sandstone.

Analysis of energy dissipation and crack evolution law of sandstone under impact load

2020 ◽  
Vol 132 ◽  
pp. 104359 ◽  
Author(s):  
Yi Luo ◽  
Gang Wang ◽  
Xinping Li ◽  
Tingting Liu ◽  
Abhay Kumar Mandal ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Impact Load ◽  
Crack Evolution ◽  
Evolution Law

scholarly journals Experimental Study on Mechanical Properties of Prefabricated Single-Cracked Red Sandstone under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yue Yuan ◽  
Jinlei Fu ◽  
Xiaolei Wang ◽  
Xi Shang
Keyword(s):  
Mechanical Properties ◽  
Crack Propagation ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Contact Force ◽  
Rock Sample ◽  
Unstable Fracture ◽  
Red Sandstone ◽  
Rock Samples ◽  
Dip Angle

This paper aims at the phenomenon of the fractured rock column in underground engineering which is prone to collapse when subjected to ground pressure. Uniaxial compression test and particle flow code (PFC2D) are used to analyze the influence of crack dip angle on the mechanical properties, crack propagation, and the failure mode of red sandstone. From the results, it is observed that the stress–strain curve of the precracked red sandstone can be divided into five stages, and there is a critical stress value in the stage of accelerated crack propagation and unstable fracture of the rock sample. Further, the peak strength, maximum strain, and the elastic modulus of the precracked red sandstone increase with the increase of crack dip angle, and the ultimate failure mode of rock sample changes from the “ladder” type failure to slope uneven failure. Furthermore, from PFC2D simulation, it is found that the tensile microcracks contribute more towards the failure of rock samples than the shear cracks. The contact force chain is very weak at the places where the precracks and macroshear planes are formed. This indicates that the original contact force is weakened due to particle fracture. Therefore, the bearing capacity of the precracked rock samples decreases with the increase in load. From the simulation results, it is found that the displacement at the shear plane of the rock sample is large, and the shear dilatation occurs. With the increase in load, the specimen falls off and is ejected. This is due to the weakening of the contact force between the internal particles. Thereafter, it fractures to produce microcracks, which gradually converge, thus providing a prerequisite for the transformation of elastic strain energy into kinetic energy.

Influence of Geometrical Imperfection on Failure Mode of DP780 Steel Utilizing Damage Models Embedded RVE Technique

2016 ◽  
Vol 725 ◽  
pp. 471-476
Author(s):  
Kun Zhao ◽  
Xin Cun Zhuang ◽  
Xin Hua Pei ◽  
Zhen Zhao
Keyword(s):  
Failure Mode ◽  
Structural Heterogeneity ◽  
Dual Phase ◽  
Crack Initiation And Propagation ◽  
Crack Evolution ◽  
Dp Steel ◽  
Damage Models ◽  
Geometrical Imperfection ◽  
Initiation And Propagation ◽  
Dp780 Steel

As dual-phase (DP) steel sheet is widely used in automotive manufacture, researches on failure mode of DP steel have been carried out experimentally and numerically in recent years. In this paper, failure mode of DP 780 steels with geometrical imperfection, which was assumed as a consequence of previous process, was investigated via a microstructure approach utilizing RVE technique. Multiple damage models were applied on characteristic microstructures and the modified pointed-ended geometrical imperfection was ingrained. Considering the progress of crack evolution, the depth and the location of geometrical imperfection were critical factors in determining the mode of crack initiation and propagation. Essentially, geometrical imperfection influenced the failure mode of investigated DP steel via aggravating the structural heterogeneity.

Analytical electron microscopy of grain boundaries in Al-Cu metallizations

1992 ◽  
Vol 50 (2) ◽  
pp. 1684-1685
Author(s):  
J. R. Michael ◽  
A. D. Romig ◽  
D. R. Frear
Keyword(s):  
Electron Microscopy ◽  
Integrated Circuits ◽  
Failure Mode ◽  
Current Density ◽  
Thermal History ◽  
Analytical Electron Microscopy ◽  
Cu Metallization ◽  
Analytical Electron ◽  
Interconnect Lines

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits, the Cu being added since it improves resistance to electromigration failure. As linewidths decrease to submicrometer dimensions, the current density carried by the interconnect increases dramatically and the probability of electromigration failure increases. To increase the robustness of the interconnect lines to this failure mode, an understanding of the mechanism by which Cu improves resistance to electromigration is needed. A number of theories have been proposed to account for role of Cu on electromigration behavior and many of the theories are dependent of the elemental Cu distribution in the interconnect line. However, there is an incomplete understanding of the distribution of Cu within the Al interconnect as a function of thermal history. In order to understand the role of Cu in reducing electromigration failures better, it is important to characterize the Cu distribution within the microstructure of the Al-Cu metallization.

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