scholarly journals Study on Mechanical Properties and Damage Evolution Law of Secondary Destruction Induced by Simultaneous Unloading after the Peak of the Curve of Sandstone

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Xiao Fukun ◽  
Liu Gang ◽  
Cheng Qianlong
Keyword(s):  
Mechanical Properties ◽  
Release Rate ◽  
Axial Strain ◽  
Confining Pressure ◽  
Primary Energy ◽  
The Body ◽  
Stress Release ◽  
Damage Degree ◽  
Damage Process ◽  
Plasticity Coefficient

The research adopts the French ROCK600-50 three-axis experiment instrument and SH-II system to evaluate the acoustic emission (AE) peak of the rear axle of yellow sandstone by carrying out the confining pressure synchronous unloading experiment, and evolution of mechanical properties and characteristics of energy transformation and damage of a yellow sandstone, which is a two-damage process, the results of which have shown the following: (1) there are two damages appearing when the confining pressure is 5 MPa, 10 MPa, and 20 MPa. In contrast, these two damages do not appear when the confining pressure is 30 MPa and 40 MPa. The fracture degree and crack number of the two fractures are larger than those without two damages. (2) A failure stress release rate showed an obvious “√” trend. With the increase of confining pressure, the stress release rate of the two failures is increasing. (3) By keeping the strain of the body constant, it is determined to be the first time to destroy the warning. The two failures of rock are predicted by the inflection point of the axial strain slope. No two failures occurred, and the strain unloading process showed two characteristics. (4) Meanwhile, with the increase of confining pressure, the energy released from the peak decreases first and then increases; the law of releasing energy from one failure and two destructions is the opposite. No damage occurred two times. As the confining pressure increases, there is a continuous decrease of the energy released from the peak. As the confining pressure increases, the release rate of the primary energy decreases at first and then increases, and the rate of energy released two times is increasing. The plasticity coefficient shows the trend of increasing first and then decreasing. (5) The damage degree of the second rupture is greater than the first rupture.

Study on Mechanical Property of Structural Damaged Expansive Soil with CT-Triaxial Shear Test

2012 ◽  
Vol 599 ◽  
pp. 811-814
Author(s):  
Lang Jing Shi ◽  
Xian Li ◽  
Zhen Peng ◽  
Shi Ji Wang ◽  
Fan Wu
Keyword(s):  
Mechanical Property ◽  
Axial Stress ◽  
Axial Strain ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Ct Images ◽  
Shear Tests ◽  
Triaxial Shear Test ◽  
Damage Area ◽  
Damage Degree

A series of CT-triaxial shear tests were conducted on expancive soil specimens under controlled suction and confining pressure as 50kPa and 100kPa. The derivative and axial stress in each stage and CT images of inner structure of specimens were obtained .The results show that the different damage location and damage degree on expansive soil samples have different effect on soil mechanical property. The deviatoric stress of smaller damage area sample is larger than of bigger damage area specimen when the damage locates at the same place. The deviatoric strain is independent of the damage degree of samples. The CT images show that with the axial strain increasing, the fissures in soil close gradually, the density of soil increases, and the deformation of samples gets larger with the increase of confining pressure.

Experimental Research on Physical and Mechanical Properties of High-Speed Railway Subgrade Filler

2014 ◽  
Vol 496-500 ◽  
pp. 2533-2537
Author(s):  
Xiong Shi ◽  
Jia Sheng Zhang ◽  
Guo Dong Deng ◽  
Fei Meng
Keyword(s):  
Mechanical Properties ◽  
Strain Hardening ◽  
High Speed ◽  
Large Scale ◽  
Axial Strain ◽  
Volumetric Strain ◽  
Bottom Layer ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Dry Density

In order to reveal the mechanical properties of the subgrade fillers, they are studied by screening test of coarse-grained soils, compaction test and large-scale triaxial test in the track-subgrade model in high-speed rail laboratory of Central South University. The experimental results show that the coarse particle content for filler of the bottom layer is larger than that of the underlying embankment. The optimum water content of the filler of the bottom layer is less than that of the underlying embankment, while the maximum of dry density is similar, All samples have shown strain hardening characteristic, the higher the confining pressure is, the more obvious the strain hardening characteristic is. the volumetric strain of samples changes from shear contraction to shear dilation with the increment of axial strain. The cohesion and internal friction angle for filler of the bottom layer is greater than that of the underlying embankment. The tangent modulus for filler of the bottom layer is larger than that of the underlying embankment, and with the confining pressure increases, the difference also increases.

scholarly journals Discrete Element Simulation Analysis of Biaxial Mechanical Properties of Concrete with Large-Size Recycled Aggregate

2021 ◽  
Vol 13 (13) ◽  
pp. 7498
Author(s):  
Tan Li ◽  
Jianzhuang Xiao
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Strain Curve ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Model ◽  
Large Size

Concrete made with large-size recycled aggregates is a new kind of recycled concrete, where the size of the recycled aggregate used is 25–80 mm, which is generally three times that of conventional aggregate. Thus, its composition and mechanical properties are different from that of conventional recycled concrete and can be applied in large-volume structures. In this study, recycled aggregate generated in two stages with randomly distributed gravels and mortar was used to replace the conventional recycled aggregate model, to observe the internal stress state and cracking of the large-size recycled aggregate. This paper also investigated the mechanical properties, such as the compressive strength, crack morphology, and stress–strain curve, of concrete with large-size recycled aggregates under different confining pressures and recycled aggregate incorporation ratios. Through this research, it was found that when compared with conventional concrete, under the confining pressure, the strength of large-size recycled aggregate concrete did not decrease significantly at the same stress state, moreover, the stiffness was increased. Confining pressure has a significant influence on the strength of large-size recycled aggregate cocrete.

scholarly journals Novel Hydrogels of Chitosan and Poly (vinyl alcohol) Reinforced with Inorganic Particles of Bioactive Glass

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 691
Author(s):  
O. Sánchez-Aguinagalde ◽  
Ainhoa Lejardi ◽  
Emilio Meaurio ◽  
Rebeca Hernández ◽  
Carmen Mijangos ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Drug Release ◽  
Bioactive Glass ◽  
Vinyl Alcohol ◽  
Release Kinetics ◽  
The Body ◽  
Poly Vinyl Alcohol ◽  
X Ray Diffraction ◽  
Inorganic Particles ◽  
Release Studies

Chitosan (CS) and poly (vinyl alcohol) (PVA) hydrogels, a polymeric system that shows a broad potential in biomedical applications, were developed. Despite the advantages they present, their mechanical properties are insufficient to support the loads that appear on the body. Thus, it was proposed to reinforce these gels with inorganic glass particles (BG) in order to improve mechanical properties and bioactivity and to see how this reinforcement affects levofloxacin drug release kinetics. Scanning electron microscopy (SEM), X-ray diffraction (XRD), swelling tests, rheology and drug release studies characterized the resulting hydrogels. The experimental results verified the bioactivity of these gels, showed an improvement of the mechanical properties and proved that the added bioactive glass does affect the release kinetics.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Influence of the mechanical stretch property of fabrics on the wear comfort of men’s suit pants

2021 ◽  
pp. 004051752110191
Author(s):  
Hiroyuki Kanai ◽  
Kentaro Ogawa ◽  
Tetsu Sasagawa ◽  
Kiyohiro Shibata
Keyword(s):  
Mechanical Properties ◽  
Pressure Measurement ◽  
Mechanical Stretch ◽  
The Body ◽  
Weft Yarn ◽  
Elongation Ratio ◽  
Weft Direction ◽  
Wear Comfort ◽  
Finishing Process ◽  
Elastic Thread

The stretch property of fabrics is one of the most important factors that provide comfort to wearers. It is expected that tension building up in the fabric can be relaxed and the garment pressure on the body can be reduced by appropriately exploiting its stretch property. Currently, the stretch property is predominantly realized using spandex. However, weaving or knitting elastic threads cannot be employed for the worsted fabric used to design men’s suits because of their effects on the mechanical properties of the fabric (e.g., embrittlement), which deteriorate with time. In this study, worsted fabric with a graded mechanical stretch property was produced, and the effect of the mechanical stretch property on comfort was verified. The mechanical stretch property is developed from the tension relaxation and fabric shrinkage along the weft yarn during the crabbing, scouring, and drying stages of the finishing process. Then, the form of the fabric is set by heating. In this study, the worsted fabric had an elongation ratio varying from 5.9% to 16.1% along the weft direction that was produced without using elastic thread. Furthermore, men’s suit pants were made from the fabrics. The effect of the stretch property on the garment comfort was verified through sensory evaluation and garment pressure measurement. The contribution of the mechanical stretch property in improving the garment comfort of men’s suit pants is discussed.

scholarly journals Injectable non-leaching tissue-mimetic bottlebrush elastomers as an advanced platform for reconstructive surgery

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Erfan Dashtimoghadam ◽  
Farahnaz Fahimipour ◽  
Andrew N. Keith ◽  
Foad Vashahi ◽  
Pavel Popryadukhin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reconstructive Surgery ◽  
Biomedical Applications ◽  
The Body ◽  
Surrounding Tissue ◽  
Curing Time ◽  
Materials Used ◽  
Significant Health

AbstractCurrent materials used in biomedical devices do not match tissue’s mechanical properties and leach various chemicals into the body. These deficiencies pose significant health risks that are further exacerbated by invasive implantation procedures. Herein, we leverage the brush-like polymer architecture to design and administer minimally invasive injectable elastomers that cure in vivo into leachable-free implants with mechanical properties matching the surrounding tissue. This strategy allows tuning curing time from minutes to hours, which empowers a broad range of biomedical applications from rapid wound sealing to time-intensive reconstructive surgery. These injectable elastomers support in vitro cell proliferation, while also demonstrating in vivo implant integrity with a mild inflammatory response and minimal fibrotic encapsulation.

Experimental Study on the Combined Effect of Cyclic and Static Loads on the Mechanical Properties of the Saturated Soft Clay Material

2016 ◽  
Vol 723 ◽  
pp. 843-848
Author(s):  
Yi Wei ◽  
Ying Zhu ◽  
Jing Ni
Keyword(s):  
Mechanical Properties ◽  
Cyclic Load ◽  
Stress Ratio ◽  
Axial Strain ◽  
Soft Clay ◽  
Cyclic Stress ◽  
Excess Pore Pressure ◽  
Static Loads ◽  
Cyclic Stress Ratio ◽  
Excess Pore

The combined effect of cyclic and static loads on the mechanical properties of the soft clay was experimentally investigated by conducting undrained cyclic triaxial tests on Shanghai clay. The results show that an increment in either static or cyclic load increases excess pore pressures and axial strains. For a given value of combined cyclic and static loads, the mechanical properties of the soft clay are more sensitive to the cyclic load. Furthermore, the accumulated excess pore pressure and axial strain for a larger cyclic stress ratio and a lower combined stress ratio might overcome that for a lower cyclic stress ratio and a higher combined stress ratio. The mechanical properties of the soft clay after the cyclic load was unloaded were also discussed. It was observed that the excess pore pressure and axial strain under the static load alone decrease gradually with time. The trend of them largely depends on the ratio of cyclic load to static load.

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