scholarly journals Laboratory Study on Changes in Gas Desorption Properties of Anthracite after Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tie Li ◽  
Dong Wang ◽  
Mei-Hua Liu ◽  
Liang Chen ◽  
Hao Liu
Keyword(s):  
Diffusion Coefficient ◽  
Cyclic Loading ◽  
Testing Machine ◽  
Coal Mass ◽  
Shanxi Province ◽  
Loading Frequency ◽  
Test Results ◽  
Gas Desorption ◽  
Initial Stage ◽  
Desorption Capacity

Coal mass is subjected to cyclic loading during pulsating hydraulic fracturing (PHF), and changes in its gas desorption properties affect gas drainage. Therefore, it is of great importance to correctly understand the influences of cyclic loading on the gas desorption properties of coal mass. Firstly, loading tests with different frequencies and amplitudes were performed on anthracite from Qinshui Basin (Shanxi Province, China) using a fatigue testing machine. Secondly, gas desorption tests were performed to determine the associated curves for each test group at different equilibrium pressures, and the initial desorption capacity and diffusion coefficient of the gas were calculated. Finally, the influence of different loading conditions on the gas desorption laws were analyzed. The test results demonstrate that a greater loading frequency increases the ratio of the initial desorption capacity so that the desorption rate of coal samples is higher, and the gas desorption properties become increasingly better in the initial stage. However, variations in the amplitude have minimal impact on the ratio of the initial desorption capacity. When the amplitude is too large in the initial stage, the diffusion coefficient decreases and the gas desorption properties worsen. In addition, the above test results are used to discuss the selection of the amplitude and frequency in the PHF process from a macroperspective. The contained research results provide an important theoretical basis for the field application of PHF technologies in coal mines.

scholarly journals Effects of Cyclic Loading on the Pore Structure of Anthracite Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Dong Wang ◽  
Tie Li ◽  
Zhiheng Cheng ◽  
Weihua Wang
Keyword(s):  
Cyclic Loading ◽  
Hydraulic Fracturing ◽  
Pore Structure ◽  
Wave Amplitude ◽  
Testing Machine ◽  
Sine Wave ◽  
Shanxi Province ◽  
Loading Frequency ◽  
Anthracite Coal ◽  
Pulse Hydraulic Fracturing

In the process of improving coalbed permeability through pulse hydraulic fracturing, the cyclic loading effect influences the characteristics of micropores in coal matrix, thus affecting the process of gas migration. Therefore, it is essential to investigate the effect of cyclic loading on the pore structure of coal. Seven groups of loading tests at different frequencies and amplitudes were conducted on anthracite coal obtained from Shanxi Province, China, using a fatigue-testing machine. Subsequently, using a PoreMaster GT-60 Mercury-intrusion apparatus, the influence of the frequency and amplitude on the structural characteristics (including mercury-injection and mercury-ejection curves, pore size distribution, porosity, and specific surface area) of pores in coal samples was analyzed. Finally, the law and mechanism of action of the loading frequency and amplitude on pores in coal samples were comprehensively analyzed. The test results showed that, in the case of maintaining the sine-wave amplitude unchanged during loading while altering the loading frequency, the overall porosity and pore volume rise at different degrees. The growth of the loading frequency presents a more significant promotive effect on the initiation and development of pores and fractures. Moreover, it drives the transformation of micropores and transition pores into mesopores and macropores, thus increasing the proportion of seepage pores. Under the condition of large sine-wave amplitude during loading, macropores and mesopores are subjected to the repeated action of the external force, thereby reducing the overall porosity. In addition, the volume of the seepage pores declines, and the number of the coalesced pores decreases. Finally, in light of these results, the implications of frequency and amplitude selection in the process of pulse hydraulic fracturing are discussed. Therefore, the results of this research will provide an important theoretical basis for the field application of pulse hydraulic fracturing technology in coal mines.

On Using Stress Relaxation Tests to Characterize Material Behavior

1987 ◽  
Vol 54 (2) ◽  
pp. 346-350 ◽  
Author(s):  
J. L. Ding ◽  
W. N. Findley
Keyword(s):  
Stress Relaxation ◽  
Strain Rate ◽  
Testing Machine ◽  
Inelastic Strain ◽  
Material Behavior ◽  
Test Results ◽  
Creep Data ◽  
Total Stress ◽  
Initial Stage ◽  
Rate Relation

Stress relaxation tests, in which the gage length of the specimen was maintained constant by servocontrol, were performed on 2618-T61 aluminum. The test results, which were independent of the stiffness of the testing machine, were converted into a relation between stress and inelastic strain rate. It was found that the contribution by the anelastic component to the total stress relaxation was significant only in the initial stage. The validity of using the obtained stress versus inelastic-strain-rate relation to characterize the material behavior is also discussed. Results do not substantiate the concept of a “hardness” flow curve, but data were well predicted from the creep data by theory based on strain hardening and viscoelasticity.

scholarly journals Study of the Mechanical Environment of Chondrocytes in Articular Cartilage Defects Repaired Area under Cyclic Compressive Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Hai-Ying Liu ◽  
Hang-Tian Duan ◽  
Chun-Qiu Zhang ◽  
Wei Wang
Keyword(s):  
Articular Cartilage ◽  
Cyclic Loading ◽  
Response Curve ◽  
Fluid Pressure ◽  
Cartilage Defects ◽  
Loading Frequency ◽  
Liquid Pressure ◽  
Mechanical Environment ◽  
Finite Element Software ◽  
Maximum Value

COMSOL finite element software was used to establish a solid-liquid coupling biphasic model of articular cartilage and a microscopic model of chondrocytes, using modeling to take into account the shape and number of chondrocytes in cartilage lacuna in each layer. The effects of cyclic loading at different frequencies on the micromechanical environment of chondrocytes in different regions of the cartilage were studied. The results showed that low frequency loading can cause stress concentration of superficial chondrocytes. Moreover, along with increased frequency, the maximum value of stress response curve of chondrocytes decreased, while the minimum value increased. When the frequency was greater than 0.2 Hz, the extreme value stress of response curve tended to be constant. Cyclic loading had a large influence on the distribution of liquid pressure in chondrocytes in the middle and deep layers. The concentration of fluid pressure changed alternately from intracellular to peripheral in the middle layer. Both the range of liquid pressure in the upper chondrocytes and the maximum value of liquid pressure in the lower chondrocytes in the same lacunae varied greatly in the deep layer. At the same loading frequency, the elastic modulus of artificial cartilage had little effect on the mechanical environment of chondrocytes.

Molten Slag Structure and Diffusion Coefficients of Cr3+ and Si4+ during Micro-Carbon Cr-Fe Alloy Production

2011 ◽  
Vol 79 ◽  
pp. 77-82
Author(s):  
Yi Min ◽  
Jian Huang ◽  
Cheng Jun Liu ◽  
Mao Fa Jiang
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Molten Slag ◽  
Optimization Method ◽  
Structure Theory ◽  
Average Diffusion Coefficient ◽  
Slag Structure ◽  
Initial Stage ◽  
Silicate Structure ◽  
Average Diffusion

Based on the silicate structure theory, the molten slag structure and the existential state of and during micro-carbon Cr-Fe alloy production process were analysised, and then their diffusion coefficients were calculated. The results showed that, during the initial stage, the average diffusion coeffecient of and is close to the , the reaction process is controlled by the diffusion of () and corporately, during the later stage, the diffusion coefficient of is less than average diffusion coefficient of and , the controlling step is the diffusion of . According to the evolution of diffusion coefficient, molten slag composition optimization method was advised to increase the diffusion ability of and for enhancing the reaction efficiency and the recovery rate of chromium.

The Properties of Welded Joints Made by 6082-T6 Aluminium Alloy and their Behaviour under Cyclic Loading Conditions

2015 ◽  
Vol 812 ◽  
pp. 375-380 ◽  
Author(s):  
D. Pósalaky ◽  
János Lukács
Keyword(s):  
Cyclic Loading ◽  
Automotive Industry ◽  
Welded Joints ◽  
Structural Engineering ◽  
Physical Simulation ◽  
Base Material ◽  
Point Of View ◽  
Test Results ◽  
Structural Elements ◽  
Effective Use

The magnitude of different aluminium alloys, especially the ones with higher strength, are increasing in the structural engineering, not just the usual applications (like the aerospace industry) but more likely in the automotive industry. There are more assumptions of the effective use of aluminium; we should highlight two important factors, the technological and the applicability criterions. The technological criterion is the joining of structural elements, frequently with welding thus the technological criterion ultimately is the weldability. The assumption of applicability comes from the loading capability of these structures, which is typically cyclic loading so the key issue from the point of view of applicability is the resistance to fatigue. This article represents physical simulation and fatigue test results both on the base material and on the welded joints.

scholarly journals Design Go-Kart Chassis Four Strokes 110 Engine

2021 ◽  
Vol 2 (1) ◽  
pp. 17-20
Author(s):  
Misbachuddin
Keyword(s):  
Tensile Testing ◽  
Testing Machine ◽  
Computer Application ◽  
Test Results ◽  
Welding Wire ◽  
Tensile Testing Machine ◽  
Elasticity Limit ◽  
Steel Pipes ◽  
Auto Cad ◽  
A Current

 This study aimed to decide how to design a kart chassis and the strength of the welded joints. In this design, the chassis frame is made of tubular profile steel, which is designed to withstand most of the loads in a vehicle. The chassis was designed using a computer application, namely Auto CAD 2007. Assembly using carbon steel pipes connected using SMAW welding with E6013 RB 2.6 mm welding wire with a current of 75 A, 1G place. The test is carried out with a tensile testing machine. The material is pulled past the most stretch elasticity limit until finally, the specimen reaches the limit (breaks). The tensile test takes about 3-5 minutes with a load of 10-20N. The test results show the average tensile strength of the iron pipe is 0.512 Mpa.

scholarly journals The Effect of Imidazolium-Based Ionic Liquids on the Tensile Properties of Gellan Gum/KCF Biocomposite Films - A Prelude Study

2021 ◽  
pp. 1-10
Author(s):  
Ahmad Adlie Shamsuri ◽  
Khalina Abdan ◽  
Tatsuo Kaneko
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Tensile Properties ◽  
Testing Machine ◽  
Tensile Modulus ◽  
Gellan Gum ◽  
Mixed Solution ◽  
Test Results ◽  
Biocomposite Films ◽  
Biocomposite Film

In this prelude study, the gellan gum/kenaf core fiber (KCF) biocomposite films were fabricated with the addition of imidazolium-based ionic liquids such as 1-butyl-3-methylimidazolium chloride (Bmim Cl), 1,3-dimethylimidazolium methylsulphate (Dmim MeSO4), 1-ethyl-3-methylimidazolium acetate (Emim Ac), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (Emim OTf). The fabrication of the biocomposite films was carried out by mixing KCF and the ionic liquids in an aqueous solution, followed by dissolution of gellan gum in the same solution at a temperature of 90°C. The mixed solution was gelled at room temperature, and the formed gel was dried in an oven at 40°C for 48 hours to obtain a freestanding biocomposite film. The fabricated films were characterized by using a universal testing machine to acquire tensile properties. The tensile test results indicated that the biocomposite film added with Emim Ac possesses a higher tensile extension at maximum (up to 24%) than the biocomposite film without ionic liquid (added with glycerol). In addition, the biocomposite film added with Emim OTf has a higher tensile modulus at maximum (up to 758%) compared to the biocomposite film without ionic liquid. In conclusion, the tensile properties of the gellan gum/KCF biocomposite films can be improved with the addition of Emim-based ionic liquids with different counter anions.

Temperature effects on ageing properties and diffusivity of a HDPE GM in landfill

2021 ◽  
pp. 0734242X2110570
Author(s):  
Shengwei Wang ◽  
Tao Guo ◽  
Huan Tian ◽  
Zhigang Li ◽  
Kang Fei
Keyword(s):  
Diffusion Coefficient ◽  
Tensile Properties ◽  
Ageing Time ◽  
Melt Flow Index ◽  
Engineering Properties ◽  
Flow Index ◽  
Test Results ◽  
Oxidation Induction Time ◽  
Degradation Rates ◽  
And Migration

High-density polyethylene (HDPE) geomembranes (GMs) play a crucial role in preventing the leakage and migration of pollutants. GM service life and ageing properties are the main concerns for the choice of materials. However, it is not clear how the mechanical properties and anti-fouling performance of geomembranes change with ageing time. To solve this problem, a HDPE GM was selected for testing under exposed air condition. The tests included oxidation induction time (OIT), melt flow index (MFI), tensile properties and diffusivity under four temperature conditions for 1½ years. The test results showed that the GM has higher OIT degradation rates. Stage I – depletion of antioxidants occurred at only 10 years for the GM, which was approximately 1/4 that of the GM-GSE. The GM engineering properties index showed the same changes as those of the GM-GSE. However, MI rapidly decreased with the incubation time. The molecular weight degradation of the GM was approximately 57% and far greater than that of GM-GSE after 15 months, but the tensile properties of the two GMs showed little change. The diffusion coefficient Di of GM increases gradually with the increase of temperature in methane and trichloromethane. Under the same conditions, the diffusion coefficient Di of the GM in methane is significantly higher than that in trichloromethane, indicating that the GM has better barrier to trichloromethane.

scholarly journals Material properties of Velcro fastenings

1982 ◽  
Vol 6 (2) ◽  
pp. 93-96
Author(s):  
D. L. Bader ◽  
M. J. Pearcy
Keyword(s):  
Cyclic Loading ◽  
Material Properties ◽  
Testing Machine ◽  
Force Extension ◽  
Instron Testing Machine ◽  
Attachment Strength

An assessment of the material properties of three types of touch and close fasteners (Velcro) in general orthopaedic usage is presented. The materials were tested under various loading regimes using an Instron testing machine. The force-extension curves were analyzed and values determined for both the stiffness and strength of the various attachments. Particular reference was made to the alteration in attachment strength after cyclic loading. The strength of the standard Velcro was found to be least affected after cyclic loading to simulate continuous usage. A recommendation is made on the specific application of each type of Velcro based on their material properties.

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