scholarly journals Experimental Studies on Cracking and Local Strain Behaviors of Rock-Like Materials with a Single Hole before and after Reinforcement under Biaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jian Liao ◽  
Yanlin Zhao ◽  
Liming Tang ◽  
Qiang Liu
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Peak Strength ◽  
Biaxial Compression ◽  
Tensile Cracks ◽  
Fracture Surfaces ◽  
Single Hole ◽  
Aluminum Alloy Tube

In deep underground engineering, circular roadways are widely used; many rock engineering problems can usually be simplified as mechanical analysis of rock structures with holes. To reveal the influence of intrahole reinforcement on the mechanical properties of rock with a single hole, this paper takes the single-hole rock-like material specimens with different reinforcement conditions as the research object. The RYL600 rock shear rheometer was used to conduct biaxial compression tests and, combined with HD industrial cameras and high-precision strain gauges, to study the effects of different reinforcement thicknesses and different lateral pressure on the mechanical properties of single-hole rock-like materials during the total stress and strain process. The thickness of the reinforced aluminum alloy pipe in the whole test is divided into four types: 0, 1, 1.5, and 2 mm. Under different reinforcement conditions, it is divided into 4 series of 0, 0.5, 1, and 1.5 MPa according to the different lateral pressure. Research shows the following: (1) Under the same lateral pressure, as the reinforcement thickness of the aluminum alloy tube increases, the reinforcement effect of the aluminum alloy tube on the specimen increases, and the strength of the reinforced specimen is increased by 1.42%~33.04% compared with the strength of the unreinforced specimen; under the same reinforced thickness of the aluminum tube, the peak strength of the specimen increases with the increase of lateral pressure, and the peak strength of the specimen with lateral pressure is 3.34%~50.26% higher than that of the specimen without lateral pressure. (2) Increasing the lateral pressure can significantly reduce the primary tensile cracks of the specimen. As the reinforcement thickness increases, the primary tensile cracks and remote cracks of the specimen are significantly reduced, and the failure surface of the specimen gradually tends to the middle of the sample. (3) The failure modes of specimens with holes can be divided into five types: single bevel type I, single bevel type II, single bevel type III, bevel T type, and single part shear type. All of these five failure modes are shear cracks that develop into fracture surfaces, while remote cracks and primary tensile cracks do not develop into fracture surfaces.

scholarly journals Mechanical properties and progressive failure characteristics of sandstone containing elliptical and square openings subjected to biaxial stress

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0246815
Author(s):  
Honggang Zhao ◽  
Haitao Sun ◽  
Dongming Zhang ◽  
Chao Liu
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Failure Modes ◽  
Biaxial Stress ◽  
Tensile Fracture ◽  
Biaxial Compression ◽  
Lateral Stress ◽  
Variable Theory ◽  
Failure Characteristics ◽  
Elliptical Opening

Two kinds of common tunnel shapes, i.e. elliptical opening and square opening were selected for biaxial compression tests, and the influences of two kinds of opening shapes on the mechanical properties, failure characteristics and failure modes of sandstone were compared and analyzed. The complex variable theory and mapping functions were used to obtain the analytical stress solution around elliptical and square openings. The results show that the stability of the specimen containing an elliptical opening was better than that of the specimen containing a square opening under the same lateral stress. Compared with the elliptical opening, the local damage was formed earlier in the square opening which might be caused by a higher stress concentration around the square opening. The stress distributions around openings were influenced by the opening shape and lateral stress coefficient. The top and bottom of square opening were more prone to tensile fracture, and the distribution range of tensile was larger than that of elliptical opening. When the opening failed, the intensity of square opening failure was weaker than that of elliptical opening. On the basis of the average frequency value and the rise angle value, the failure mode of specimen containing elliptical or square opening was distinguished. It was found that the mixed tension and shear failure dominated the failure of specimens with different opening shapes, and the number of shear cracks in the specimen containing a square opening was greater than that in the specimen containing an elliptical opening. The above method of judging failure mode by acoustic emission signals was well verified by the CT images of damaged specimens.

Effect of Artificial Aging on the Mechanical Properties of an Aerospace Aluminum Alloy 2024

2012 ◽  
Vol 326-328 ◽  
pp. 193-198 ◽  
Author(s):  
Danieli A.P. Reis ◽  
Antônio Augusto Couto ◽  
N.I. Domingues Jr. ◽  
Ana Cláudia Hirschmann ◽  
S. Zepka ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Aluminum Alloy ◽  
Specific Weight ◽  
Tensile Tests ◽  
Test Machine ◽  
Constant Frequency ◽  
Fracture Surfaces ◽  
Heat Treated ◽  
Aluminum Alloy 2024

Aluminum alloys have low specific weight, relatively high strength and high corrosion resistance and are used in many applications. Aluminum Alloy 2024 is widely used for aircraft fuselage structures, owing to its mechanical properties. In this investigation, Aluminum Alloy 2024 was given solid solution treatments at 495, 505, and 515°C followed by quenching in water. It was then artificially aged at 190 and 208°C. Subsequently, hardness measurements, tensile tests as well as impact and fatigue tests were carried out on the heat treated alloys to determine the mechanical properties. The tensile and hardness tests revealed similar mechanical properties for specimens of this alloy that were given the three solid solution treatments. Aluminum Alloy 2024 specimens that were solid solution treated at 515°C and artificially aged at 208°C for 2h exhibited the highest yield and tensile strength. In general, the increase in strength was accompanied by a decrease in ductility. Cyclic fatigue studies were conducted with symmetric tension-compression stresses at room temperature, using a bending-rotation test machine. The alloy solution heat treated at 515°C and aged at 208°C/2h was fatigue tested at constant frequency. The relation between stress amplitude and cycles to failure was established, enabling the fatigue strength to be predicted at more than 7.8x106cycles, with maximum stress of 110.23 MPa. The fracture surfaces of specimens that failed after fewer cycles showed mainly precipitates and micro voids, whereas specimens that fractured after a higher number of cycles indicated that cracks initiated at the surface. The high cycle fatigue fracture surfaces revealed pores that could be due to precipitates from the matrix.

scholarly journals Analysis of Biaxial Mechanical Properties and Failure Criterion of Self-Compacting Concrete

2021 ◽  
Vol 8 ◽  
Author(s):  
Jun Zhang ◽  
Chen Li ◽  
Congxiang Zhu ◽  
Zhiqing Zhao
Keyword(s):  
Mechanical Properties ◽  
Principal Stress ◽  
Compressive Stress ◽  
Failure Modes ◽  
Biaxial Loading ◽  
Biaxial Tension ◽  
Biaxial Compression ◽  
Self Compacting Concrete ◽  
Ordinary Concrete ◽  
Biaxial Mechanical Properties

Biaxial compression-compression, biaxial tension-compression and compression-shear tests were carried out on self-compacting concrete (SCC) using the rock true triaxial machine and compression-shear hydraulic servo machine to explore the biaxial mechanical properties of SCC. The failure modes and stress-strain curves of SCC under different loading conditions were obtained through experiment. Based on the comparison with the biaxial loading test data of ordinary concrete, the following conclusions are drawn: the failure modes and failure mechanisms under biaxial compression-compression and biaxial tension-compression are similar between SCC and ordinary concrete. Under compression-shear loading, the oblique cracks formed on the lateral surface of the specimen parallel to the shear direction gradually increased and the friction marks on the shear failure section were gradually deepened with the increase of axial compression ratio. The development trend of the stress-strain curve in the principal stress direction was not related to the lateral stress. Under the influence of lateral compressive stress, the principal compressive stress of SCC was increased by 55.78% on average; under biaxial tension-compression, the principal tensile stress of SCC had a maximum reduction of 62.79%; and under the compression-shear action, the shear stress of SCC had a maximum increase of 3.35 times. Compared with the biaxial stress test data of ordinary concrete, it can be seen that the lateral compressive stress had a more significant effect on the principal stress of SCC under biaxial loading. Subsequently, the strength criterion equations of SCC under biaxial loading were proposed based on the principal stress space and octahedral space stress respectively, which have shown good applicability in practice.

Mechanical Properties of Interpenetrating Graphite/2024Al Composites Produced by Improved Squeeze Exhaust Casting

2007 ◽  
Vol 353-358 ◽  
pp. 1471-1474 ◽  
Author(s):  
Chen Su ◽  
Gao Hui Wu ◽  
Jing Qiao ◽  
Long Tao Jiang
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Flexural Strength ◽  
Young’S Modulus ◽  
Fracture Mechanism ◽  
Room Temperature ◽  
Squeeze Casting ◽  
Young's Modulus ◽  
Fracture Surfaces ◽  
3D Network

The graphite/2024Al composites have been fabricated by improved Squeeze Exhaust Casting (SQEC) method. Two kinds of graphite preforms with porosities of 13% and 17% respectively were infiltrated with 2024Al (Al-5Cu-2Mg) alloy under the pressure of 73MPa. The disadvantages of traditional Squeeze Casting (SQC) were avoided and the distribution of aluminum alloy appeared homogenous 3D network in the composites. Flexural strength and Young’s modulus were determined at room temperature. Compared to graphite preform, the composites exhibited a significant enhancement of mechanical properties. The flexural strength and Young’s modulus of X-Y direction of G186/2024Al composites increased from 38.6MPa to 99.7MPa and from 10.1GPa to 19.7GPa, respectively. The fracture mechanism of the composites was discussed on the basis of fracture surfaces.

scholarly journals Mechanical Properties and Microstructure Evolution of Aluminum Alloy Tubes with Normal Gradient Grain Under Biaxial Stress

2021 ◽  
Author(s):  
Yang CAI ◽  
Xiaosong Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Aluminum Alloy ◽  
Biaxial Stress ◽  
Maximum Expansion ◽  
Grain Distribution ◽  
Strength And Plasticity ◽  
Hydraulic Bulging ◽  
Aluminum Alloy Tube ◽  
Size Gradient

Abstract Grain size gradient materials are a type of new structural material with the advantages of both coarse and fine grains. To study the effect of normal gradient grain on the mechanical properties and microstructure of aluminum alloy tube during hydroforming, the normal gradient grain distribution of the outer fine and inner coarse grains was obtained using spinning and annealing methods, and the biaxial stress was acquired using hydraulic bulging experiments. The thickness of the outer refined area was 105, 470, and 570 μm, respectively, where the grain size was refined to within 50 μm. Under biaxial stress, the tensile strength of the tube was 79, 89, and 106 MPa, the maximum expansion rates were 18%, 17%, and 10%, and the work-hardening indexes were 0.19, 0.20, and 0.17, respectively. The gradient grain tube with a refined thickness of 470 μm exhibited both strength and plasticity and was suitable for the hydroforming of aluminum alloy tubular parts. With increasing refined grain area, the density of the low angular grain boundary increased and make the chance of stitching dislocation increased in the process of intracranular deformation. However, the increase in the refined region weakened the deformation coordination, leading to a decrease in plasticity.

Discrete Element Simulation of Composite Geomaterial Talus Deposit Based on Digital Image Technology

2011 ◽  
Vol 55-57 ◽  
pp. 125-131 ◽  
Author(s):  
An Quan Xu ◽  
Wei Ya Xu ◽  
Chong Shi ◽  
Zhi Hao Xia
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Digital Image ◽  
Discrete Element ◽  
Peak Strength ◽  
Biaxial Compression ◽  
Strength Increase ◽  
Discrete Element Simulation ◽  
Element Simulation ◽  
The Impact

Talus deposit is often seen in the hydropower projects in the southwest of China. Its mechanical properties are so complex that microscopic structure study is often used to reveal the essence of deformation and damage. The digital image processing technology (DIPT) is introduced to the discrete element simulation of talus deposits. Based on the study of DIPT, a Photo-To-PFC (PTP) automodeling program is developed. It is able to realize the whole process: analyzing and processing the digital image, acquiring the information and establishing the model files. The discrete element model of talus deposit can be established fast and correctly by the PTP from the digital photo on-site. A new way is opened up for the study of the talus deposit. As an example, some talus deposit data of Gushui hydropower station is used, structure model and mechanical properties of talus deposit are studied based on DIPT and PTP. The mechanical properties are studied by the numerical simulation of biaxial compression test. The results show that the gravels and soil mass compress with each other to form a corporate load-carrying body for sharing the external forces. The stress-strain curves show a strain-hardening stage obviously due to the impact of gravels. With the increasing of bond strength among soil particles, the initial elastic modulus and peak strength of talus deposit go up at a certain level; the initial elastic modulus and peak strength increase a lot as the existence of gravels.

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