scholarly journals Molecular Simulation Study on the Microscopic Structure and Mechanical Property of Defect-Containing sI Methane Hydrate

2019 ◽  
Vol 20 (9) ◽  
pp. 2305 ◽  
Author(s):  
Shouyin Cai ◽  
Qizhong Tang ◽  
Sen Tian ◽  
Yiyu Lu ◽  
Xuechao Gao
Keyword(s):  
Mechanical Property ◽  
Methane Hydrate ◽  
Mechanical Characteristics ◽  
Strain Curve ◽  
Microscopic Structure ◽  
Stress Strain Curve ◽  
Comprehensive Utilization ◽  
Deletion Rate ◽  
Before And After ◽  
Time Of Failure

The study of changes in the related mechanical property and microscopic structure of methane hydrate during the decomposition process are of vital significance to its exploitation and comprehensive utilization. This paper had employed the molecular dynamics (MD) method to investigate the influence of defects on the microscopic structure and mechanical property of the sI methane hydrate system, and to discover the mechanical property for the defect-containing hydrate system to maintain its brittle materials. Moreover, the stress-strain curve of each system was analyzed, and it was discovered that the presence of certain defects in the methane hydrate could promote its mechanical property; however, the system mechanical property would be reduced when the defects had reached a certain degree (particle deletion rate of 9.02% in this study). Besides, the microscopic structures of the sI methane hydrate before and after failure were analyzed using the F3 order parameter value method, and it was found that the F3 order parameters near the crack would be subject to great fluctuations at the time of failure of the hydrate structure. The phenomenon and conclusions drawn in this study provide a basis for the study of the microscopic structure and mechanical characteristics of methane hydrate.

Improvement of Strength, Weibull Modulus and Damage Tolerance of SiC

2007 ◽  
Vol 561-565 ◽  
pp. 489-494 ◽  
Author(s):  
Yoshihiro Hirata ◽  
Naoki Matsunaga ◽  
Nobuhiro Hidaka ◽  
Tomoyuki Maeda ◽  
Takashi Arima ◽  
...  
Keyword(s):  
Weibull Modulus ◽  
Powder Compact ◽  
Damage Tolerance ◽  
Strain Curve ◽  
Mechanical Reliability ◽  
Average Strength ◽  
Stress Strain Curve ◽  
Sic Fiber ◽  
Nonlinear Stress ◽  
Before And After

This paper reports the significant effects of addition of 30 nm SiC, polytitanocarbosilane and SiC fabric to enhance the mechanical reliability of SiC. The flexural strengths of dense SiC hot-pressed with 800 nm particles (average strength 565 MPa for Y2O3-Al2O3 additives and 640 MPa for Yb2O3-Al2O3 additives) were enhanced to average strength 735-820 MPa by the addition of 30 nm SiC particles (25 vol%). Addition of polytitanocarbosilane (3 vol%, precursor of SiC fiber) to the bimodal SiC powder compact with Y2O3-Al2O3 additives provided more excellent mechanical properties of average strength 910 MPa, fracture toughness 5.2 MPa·m1/2 and Weibull modulus 11.3. SiC fabric and SiC (60 vol%) - Al2O3 (40 vol%) sheet of 60 micrometer thick were alternatively laminated and bonded to the surfaces of dense SiC under the pressure of 5 MPa. The SiC fabric prevented the propagation of the cracks formed by Vickers indentor and showed a significant nonlinear stress-strain curve. As a result, no change in the strength was measured before and after the introduction of cracks.

A Two-Load Method of Determining the Average True Stress-Strain Curve in Tension

1939 ◽  
Vol 6 (4) ◽  
pp. A156-A158
Author(s):  
C. W. MacGregor
Keyword(s):  
Strain Curve ◽  
True Stress ◽  
Massachusetts Institute ◽  
Massachusetts Institute Of Technology ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Before And After ◽  
Institute Of Technology ◽  
Reduction Of Area ◽  
Complete Average

Abstract The author describes a method, developed at the Massachusetts Institute of Technology, whereby the complete average true stress-strain curve in tension may be determined for a material from the beginning of yielding to fracture under ordinary testing speeds by the observation during the test of only two loads applied to a tapered specimen, namely, the maximum and fracture loads. Diameters at various positions along tapered specimens are measured before and after the test, and stress and reduction-of-area values computed from these observations.

Experimental Study on Mechanical Characteristics of Deformation of Red Sandstone

2011 ◽  
Vol 261-263 ◽  
pp. 1234-1238
Author(s):  
Rui Hong Wang ◽  
Yu Zhou Jiang ◽  
Jing Guo ◽  
Shi Yi Wen
Keyword(s):  
Rock Mass ◽  
Elastic Modulus ◽  
Mechanical Characteristics ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Confining Pressure ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Red Sandstone

For geotechnical engineering, it has great significance to research the mechanical characteristics of rock mass under three dimensional stresses. Through triaxial compression failure test, the characteristics of stress-strain curve and deformation of red sandstone from Sichuan under different confining pressures has been analyzed. The results show that: with the increment of confining pressure, the failure mode of rock mass changes from brittle failure to ductile failure gradually, and an obvious yield platform appears near the peak strength of stress-strain curve; the elastic modulus, deformation modulus, peak strain and residual strain of rock sample increase with the increment of confining pressure, the elastic modulus and deformation modulus are not a fixed value, and the relation between deformation parameter and confining pressure can be fit through quadratic curve.

Effects of collagenase and elastase on the mechanical properties of lung tissue strips

2000 ◽  
Vol 89 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Huichin Yuan ◽  
Stefanida Kononov ◽  
Francisco S. A. Cavalcante ◽  
Kenneth R. Lutchen ◽  
Edward P. Ingenito ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Connective Tissue ◽  
Guinea Pigs ◽  
Dynamic Stiffness ◽  
Harmonic Distortion ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Structural Alterations ◽  
Collagenase Treatment ◽  
Before And After

The dynamic stiffness (H), damping coefficient (G), and harmonic distortion ( k d) characterizing tissue nonlinearity of lung parenchymal strips from guinea pigs were assessed before and after treatment with elastase or collagenase between 0.1 and 3.74 Hz. After digestion, data were obtained both at the same mean length and at the same mean force of the strip as before digestion. At the same mean length, G and H decreased by ∼33% after elastase and by ∼47% after collagenase treatment. At the same mean force, G and H increased by ∼7% after elastase and by ∼25% after collagenase treatment. The k dincreased more after collagenase (40%) than after elastase (20%) treatment. These findings suggest that, after digestion, the fraction of intact fibers decreases, which, at the same mean length, leads to a decrease in moduli. At the same mean force, collagen fibers operate at a higher portion of their stress-strain curve, which results in an increase in moduli. Also, G and H were coupled so that hysteresivity (G/H) did not change after treatments. However, k d was decoupled from elasticity and was sensitive to stretching of collagen, which may be of value in detecting structural alterations in the connective tissue of the lung.

A modified version of MATLAB application window for predicting the weld bead profile and stress–strain plot of AA5052 CMT weldment using ER4043

SIMULATION ◽  
2021 ◽  
pp. 003754972110315
Author(s):  
B Girinath ◽  
N Siva Shanmugam
Keyword(s):  
Strain Curve ◽  
Weld Bead ◽  
Welding Parameters ◽  
Bead Geometry ◽  
Hybrid Technique ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Weld Bead Geometry ◽  
Inference System ◽  
Engineering Stress

The present study deals with the extended version of our previous research work. In this article, for predicting the entire weld bead geometry and engineering stress–strain curve of the cold metal transfer (CMT) weldment, a MATLAB based application window (second version) is developed with certain modifications. In the first version, for predicting the entire weld bead geometry, apart from weld bead characteristics, x and y coordinates (24 from each) of the extracted points are considered. Finally, in the first version, 53 output values (five for weld bead characteristics and 48 for x and y coordinates) are predicted using both multiple regression analysis (MRA) and adaptive neuro fuzzy inference system (ANFIS) technique to get an idea related to the complete weld bead geometry without performing the actual welding process. The obtained weld bead shapes using both the techniques are compared with the experimentally obtained bead shapes. Based on the results obtained from the first version and the knowledge acquired from literature, the complete shape of weld bead obtained using ANFIS is in good agreement with the experimentally obtained weld bead shape. This motivated us to adopt a hybrid technique known as ANFIS (combined artificial neural network and fuzzy features) alone in this paper for predicting the weld bead shape and engineering stress–strain curve of the welded joint. In the present study, an attempt is made to evaluate the accuracy of the prediction when the number of trials is reduced to half and increasing the number of data points from the macrograph to twice. Complete weld bead geometry and the engineering stress–strain curves were predicted against the input welding parameters (welding current and welding speed), fed by the user in the MATLAB application window. Finally, the entire weld bead geometries were predicted by both the first and the second version are compared and validated with the experimentally obtained weld bead shapes. The similar procedure was followed for predicting the engineering stress–strain curve to compare with experimental outcomes.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

CT Image Analysis on the Meso-Damage of Construction Waste Recycled Brick

2012 ◽  
Vol 588-589 ◽  
pp. 1930-1933
Author(s):  
Guo Song Han ◽  
Hai Yan Yang ◽  
Xin Pei Jiang
Keyword(s):  
Fractal Dimension ◽  
Strain Curve ◽  
Ct Image ◽  
Stress Strain Curve ◽  
Crack Evolution ◽  
Construction Waste ◽  
Box Counting ◽  
Industrial Ct ◽  
Ct Image Analysis ◽  
Box Counting Method

Based on industrial CT technique, Meso-mechanical experiment was conducted on construction waste recycled brick to get the real-time CT image and stress-strain curve of brick during the loading process. Box counting method was used to calculate the fractal dimension of the inner pore transfixion and crack evolution. The results showed that lots of pore in the interfacial transition zone mainly resulted in the damage of the brick. With the increase of stress, the opening through-pore appeared and crack expanded, and the fractal dimension increased.

Stress-strain curve of paper revisited

2012 ◽  
Vol 27 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Svetlana Borodulina ◽  
Artem Kulachenko ◽  
Mikael Nygårds ◽  
Sylvain Galland
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Failure Behavior ◽  
Three Dimensional Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Bonding Parameters ◽  
Particle Level ◽  
The Impact

Abstract We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

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