scholarly journals CREEP PROPERTIES AND PREDICTION MODEL OF PADDY SOIL UNDER COMPRESSION

2021 ◽  
pp. 441-451
Author(s):  
Guoyang Liu ◽  
Junfang Xia ◽  
Kan Zheng ◽  
Jian Cheng ◽  
Liu Jiang ◽  
...  
Keyword(s):  
Yield Strength ◽  
Nonlinear Model ◽  
Paddy Soil ◽  
Soil Tillage ◽  
Coefficient Of Determination ◽  
Creep Properties ◽  
Plastic Model ◽  
Burgers Model ◽  
Nonlinear Viscoelastic ◽  
Deformation Properties

In order to study the compressive creep properties and laws of paddy soil, multi-stress creep experiments of paddy soil with different moisture content were carried out. The results show that the creep deformation of paddy soil, subjected to compressive loads effect, develops stably and the paddy soil is not destructed under the yield strength when the stress is low. When the stress level is higher than the yield strength, the internal damage of paddy soil would be caused at the moment of loading. With the extension of creep time, the cracks would gradually expand, resulting in the soil to yield, break and disintegrate. According to the analysis of the deformation properties of paddy soil under compression and the change trend of creep curve, the nonlinear viscoelastic-plastic model was composed of the nonlinear viscoplastic model and Burgers model in series. The creep test curve was introduced into the model for fitting, and the coefficient of determination reached more than 0.96. Based on the model, the strain composition, strain proportion, and strain rate of paddy soil were studied. Finally, the nonlinear model was compared with Burgers model by verification test. The fitting accuracy of the nonlinear model was better than Burgers model, and the coefficient of determination and relative error were 0.997 and 0.437%, respectively, which proved the rationality and correctness of the nonlinear viscoelastic-plastic model. This study can provide a theoretical basis for the optimization of tillage machinery structure and the simulation analysis of soil tillage and compaction.

scholarly journals Energy Dissipation-Based Method for Strength Determination of Rock under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
M. M. He ◽  
F. Pang ◽  
H. T. Wang ◽  
J. W. Zhu ◽  
Y. S. Chen
Keyword(s):  
Yield Strength ◽  
Uniaxial Compression ◽  
Peak Strength ◽  
Dissipated Energy ◽  
Compression Tests ◽  
Dissipation Energy ◽  
Evolution Characteristics ◽  
Deformation Properties ◽  
Energy Coefficient ◽  
The Stability

The energy conversion in rocks has an important significance for evaluation of the stability and safety of rock engineering. In this paper, some uniaxial compression tests for fifteen different rocks were performed. The evolution characteristics of the total energy, elastic energy, and dissipated energy for the fifteen rocks were studied. The dissipation energy coefficient was introduced to study the evolution characteristics of rock. The evolution of the dissipation energy coefficient for different rocks was investigated. The linear interrelations of the dissipation energy coefficients and the yield strength and peak strength were explored. The method was proposed to determine the strength of rock using the dissipation energy coefficients. The results show that the evolution of the dissipation energy coefficient exhibits significant deformation properties of rock. The dissipation energy coefficients linearly increase with the compaction strength, but decrease with the yield strength and peak strength. Moreover, the dissipation energy coefficient can be used to determine the rock burst proneness and crack propagation in rocks.

Creep-Environment Interactions of Alloy 617 at Elevated Temperature

2008 ◽  
Author(s):  
Daejong Kim ◽  
Changheui Jang ◽  
Woo Seog Ryu
Keyword(s):  
High Temperature ◽  
Creep Strain ◽  
Elevated Temperatures ◽  
Extended Period ◽  
Nickel Base Superalloy ◽  
Environment Interaction ◽  
Creep Tests ◽  
Alloy 617 ◽  
Creep Properties ◽  
Deformation Properties

Creep behavior and degradation of creep properties of high-temperature materials often limit the lives of components and structures designed to operate for extended period under stress at elevated temperatures. A nickel-base superalloy, Alloy 617 in particular which is considered as a prospective material for hot gas duct and intermediate heat exchanger in very high temperature gas cooled reactor, was studied for creep properties. Creep tests were carried out under various sustained tensile loadings in air and helium environments at temperature of 800°C, 900°C, and 1000°C. Times for 1% creep strain and creep rupture were taken from the short-term creep tests within 1000 hours. Effect of creep-environment interaction on creep strain and changes in viscous deformation properties by dynamic recrystallization were discussed.

scholarly journals Effects of moisture content and tillage methods on creep properties of paddy soil

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253623
Author(s):  
Guoyang Liu ◽  
Junfang Xia ◽  
Kan Zheng ◽  
Jian Cheng ◽  
Jun Du ◽  
...  
Keyword(s):  
Moisture Content ◽  
Strain Rate ◽  
Rheological Properties ◽  
Paddy Soil ◽  
Paddy Soils ◽  
Rheological Parameters ◽  
No Tillage ◽  
Creep Properties ◽  
Moisture Contents ◽  
Tillage Methods

The rheological properties parameters of paddy soil affect the interaction between the tillage tools and soil, thus influencing the operation quality and power consumption. In order to study the effects of tillage methods and moisture content on the rheological properties parameters of paddy soil in the middle and lower reaches of the Yangtze River, uniaxial compression creep tests of paddy soils with four moisture contents under no tillage (moisture contents: 26.71%, 24.52%, 23.26%, 21.28%) and plough tillage (moisture contents: 26.77%, 25.55%, 23.40%, 20.56%) were carried out using a TMS-PRO texture analyzer. The creep properties curves obtained from the tests, and the rheological constitutive equation of paddy soil under compression was established by Burgers viscoelastic model. Respectively, the quantitative change rules of creep properties of paddy soil with different moisture contents under different tillage methods and the correlation between these parameters were explored. The results showed that the moisture content under the three-year plough tillage and no tillage methods had significant influence on the rheological properties parameters of paddy soil (P < 0.05). The instantaneous elastic modulus, delay elastic modulus, and viscosity coefficient of the two paddy soils (no tillage and plough tillage soils) decreased with the increase of moisture content. However, the variation rules of relaxation time and delay viscosity coefficient with moisture content differed between these two paddy soils. Specifically, the strain rate of the two paddy soils decreased as moisture content decreased, where the total strain combines elastic strain, viscous strain, and viscoelastic strain. The initial strain rate and steady strain rate of the plough tillage paddy soils were lower than that of the no tillage paddy soils. The established creep model equation could be used to obtain viscoelastic rheological parameters of paddy soil in a wide range. The fitting equations between rheological parameters and moisture content were introduced into Burgers model, and the coupling equations between creep deformation and moisture content and time were derived, which could be used to predict the creep properties and deformation behavior of paddy soil in a certain range of no tillage and ploughed field. Overall, this study has a certain theoretical significance for the development and improvement of paddy soil rheology theory, and can also provide theoretical basis and technical support for the research of agricultural machinery design optimization, field water, soil conservation, soil tillage and compaction related simulation analysis in the middle and lower reaches of the Yangtze River.

scholarly journals Evaluation of the partitioned mechanical properties and the hall-petch relationship of cast aluminum alloy cylinder head

2022 ◽  
Vol 355 ◽  
pp. 01003
Author(s):  
Kangjie Yan ◽  
Weiqing Huang ◽  
Zhengxing Zuo ◽  
Jinxiang Liu ◽  
Peirong Ren ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Aluminum Alloy ◽  
Yield Strength ◽  
Nonlinear Model ◽  
Cylinder Head ◽  
Floor Plate ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Petch Relationship

In view of the non-uniform distribution of mechanical properties of cast aluminum alloy cylinder head, the mechanical properties evaluation and microstructure heterogeneity of cylinder head were studied. The results showed that the head plate position of the cylinder head has the best mechanical properties and microstructure characterization, followed by the floor plate and the thick partition plate. The mechanical properties of the floor plate position attenuate with increasing temperature. From 23°C to 300°C, the tensile strength and yield strength decrease in the same range, but the break elongation changes most obviously. The mechanical properties and microstructure characterization of cylinder head in-situ sampling satisfy the Hall-Petch relationship. If the required ultimate tensile strength is not less than 255MPa, the upper threshold of the grain size, by considering the error limit of the Hall-Petch relationship, is 603.4μm, and the upper threshold of secondary dendrite arm spacing is 69.1μm. Meanwhile, established the relationship between hardness and yield strength, the average error of the nonlinear model is 4.35%. The prediction accuracy of the nonlinear model is sufficient to meet the actual needs of the engineering.

scholarly journals Shear Creep Properties of Weak Interlayer in Slope Based on Stationary Parameter Fractional Derivative Burgers Model

2019 ◽  
Vol 42 (3) ◽  
pp. 337-348
Author(s):  
Wen-Bo Ma ◽  
Zeng-Gang Zhao ◽  
Peng Li ◽  
Qi Liu ◽  
Cai-Qian Yang ◽  
...  
Keyword(s):  
Fractional Derivative ◽  
Shear Creep ◽  
Creep Properties ◽  
Burgers Model ◽  
Weak Interlayer

Enhanced mechanical, conductivity, and dielectric characteristics of ethylene vinyl acetate copolymer composite filled with carbon nanotubes

2017 ◽  
Vol 31 (9) ◽  
pp. 1161-1180 ◽  
Author(s):  
S Gaidukovs ◽  
E Zukulis ◽  
I Bochkov ◽  
R Vaivodiss ◽  
G Gaidukova
Keyword(s):  
Carbon Nanotubes ◽  
Yield Strength ◽  
Young’S Modulus ◽  
Vinyl Acetate ◽  
Young's Modulus ◽  
Fold Increase ◽  
Ethylene Vinyl Acetate ◽  
High Yield ◽  
Strong Interactions ◽  
Deformation Properties

We report high mechanical, dielectric, and thermal performance of carbon nanotubes (CNT) reinforced ethylene vinyl acetate (EVA) composites, fabricated using conventional melt extrusion processing. CNT have extremely high stiffness, electrical conductivity, and surface area, ensuring strong interactions with the polymer and effective reinforcement. The addition of CNT to EVA leads to an extremely high yield strength and Young’s modulus of the composites. The EVA composite produced, containing 5 wt% CNT, exhibited an almost 3-fold increase in Young’s modulus and a 2.2-fold improvement of yield strength compared to neat EVA. However, the composite maintained high deformation properties—a ductility of 1300%. Scanning electron microscopy analysis evidences the agglomeration of the CNT in the EVA/CNT composites. The EVA/CNT composites gained excellent electrostatic discharge properties—a surface resistivity in the range of 108 Ω/square. The observed thermal conductivity of the composites was increased by about 30% without losing the electrically insulating performance.

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