Study of Deformation Rule of Ordovician Limestone in Unloading of High Confining Compress

2014 ◽  
Vol 488-489 ◽  
pp. 333-336
Author(s):  
Yu Chun Yang ◽  
Xiang Min Cheng ◽  
Guo Bin Zhao ◽  
Zhi Yong Qu ◽  
Shu Wen Chen
Keyword(s):  
Loading Condition ◽  
Rock Sample ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Lateral Deformation ◽  
Bulk Deformation ◽  
Stress Strain Curve ◽  
Ordovician Limestone ◽  
Loading And Unloading ◽  
Peak Value

Under unloading condition, the characteristics of rock are different from them under loading condition. This paper talks about the characteristics of Ordovician limestone under loading and unloading condition of high compress which were taken from North Tian Mountain. The testing results indicated that: The lateral deformation and bulk deformation of rock sample are clearly in the process of unloading. Plastic deformation is not notability in the unloading condition. After the peak value in the stress-strain curve, the stress decrease quickly, it is showed that the brittleness characteristic is the better remarkable under unloading condition than loading condition. Under unloading condition, deformation modulus E50 and Possion ratio μ is quadric with the confining compress.

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.

Effect of Storage and Temperature on Flexibility of Natural and Synthetic Rubbers

1948 ◽  
Vol 21 (4) ◽  
pp. 864-876
Author(s):  
John B. Gregory ◽  
Irving Pockel ◽  
John F. Stiff
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Strain Curve ◽  
Polymer Chains ◽  
Stress Strain Curve ◽  
Low Temperature Storage ◽  
Synthetic Rubber ◽  
Loading And Unloading ◽  
Temperature Storage ◽  
Natural And Synthetic

Abstract A new method for measuring the flexibility of rubber has been described. The method consists essentially in determining the stress-strain curve obtained by loading and unloading a loop formed from a one-inch by six-inch strip cut from a test slab. A coefficient of flexibility independent of the thickness of the sample and, in addition, information on per cent resilience were obtained. By the use of the method described, the behavior of various natural and synthetic rubber gas mask facepiece compounds was studied during one month to three months' exposure at various temperatures down to −20° F. Progressive stiffening probably due to crystallization was found for natural rubber, GR-I, and GR-M compounds at low temperatures. No tendency to crystallize was noted for the GR-S compound. Of the crystallizable polymers GR-I was the most resistant, and GR-M the least resistant to stiffening during low temperature storage. It is of course evident that different polymers have inherently different degrees of resistance to low temperatures. Disregarding these inherent differences the work reported indicates that the resistance of elastomer compounds to stiffening during prolonged low temperature storage is favored by the following: 1. Use of interpolymers made from monomer mixtures having a relatively large proportion of each component, thus obtaining mutual intereference with crystallization. 2. Use of a “tight” cure which probably so impedes the movement of the polymer chains as to make crystallization difficult.

Wavelet Denoising Analysis of Rock’s Stress-Strain Curve under Uniaxial Compression

2013 ◽  
Vol 368-370 ◽  
pp. 1843-1847
Author(s):  
Li Yu ◽  
Jian Ping Chen ◽  
Wei Zheng
Keyword(s):  
Uniaxial Compression ◽  
Wavelet Packet ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Test System ◽  
Rock Stress ◽  
Wavelet Packet Analysis ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Instantaneous Deformation

Rock stress-strain curve under uniaxial compression is the output of joint action of rock and test system, so it must have certain noise. In order to realize effective denoising processing, the concept of instantaneous deformation modulus has been put forward, and the difference quotient algorithm of instantaneous deformation modulus has been used to enhance noise. After wavelet analysis and wavelet packet analysis of rock stress consequence and instantaneous deformation modulus respectively, the results of different denoising schemes have been statistically analyzed, this analysis shows that the wavelet packet analysis of instantaneous deformation modulus can achieve optimal denoising effect.

Strain Distributions around Cracks in Ductile Sheets during Loading and Unloading

1965 ◽  
Vol 7 (3) ◽  
pp. 312-317 ◽  
Author(s):  
J. R. Dixon ◽  
J. S. Strannigan
Keyword(s):  
Shear Strain ◽  
Plane Stress ◽  
Surface Coating ◽  
Fatigue Cracks ◽  
Strain Curve ◽  
Elastic Plane ◽  
Sheet Metals ◽  
Stress Strain Curve ◽  
Maximum Shear Strain ◽  
Loading And Unloading

Strain distributions around fatigue cracks in different sheet metals have been obtained by using a photoelastic surface coating with a reflection polariscope. It is shown that an estimate of the distribution of the maximum shear strain, y, near the crack tip, during both loading and unloading of the sheet, requires a knowledge of only the stress-strain curve of the material and the theoretical elastic plane-stress solution.

Experimental Study on the Shearing Property of Equal Strength Recycled Coarse Aggregate Concrete

2013 ◽  
Vol 357-360 ◽  
pp. 1420-1427 ◽  
Author(s):  
Zhi Heng Deng ◽  
Yi Liao ◽  
Chao Lou Meng ◽  
Hai Feng Yang
Keyword(s):  
Strain Curve ◽  
Recycled Concrete ◽  
Stress Strain Curve ◽  
Ordinary Concrete ◽  
Equal Strength ◽  
Shearing Strength ◽  
Shear Performance ◽  
The Difference ◽  
Shearing Strain ◽  
Peak Value

For the purpose of studying the difference between recycled concrete and ordinary concrete on shearing property under the circumstance of equal strength, nine recycled concrete beams, which have equal altitude and varying width, have been produced by using different replacement rates of 0%, 50% and 100% respectively to test their shear performance. The differences between recycled concrete and ordinary concrete on shearing strength, shearing strain and constitutive relation were analyzed in this paper. The study indicates that with the same compressive strength, there is only a slight difference between recycled concrete and ordinary concrete on shearing strength. The shearing strength of the recycled concrete is similar to the tensile strength of the ordinary concrete. Recycled concretes peak value increases as shearing strength increases. The stress-strain curve of recycled concrete is similar to that of the ordinary concrete. Its shear modulus increases when shearing strength increases.

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.

The Study of Cemented Sand and Gravel Constitutive Model

2011 ◽  
Vol 243-249 ◽  
pp. 4596-4601
Author(s):  
Ming Quan Sun ◽  
Shi Feng Yang
Keyword(s):  
Constitutive Model ◽  
Axial Strain ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cemented Sand ◽  
Shearing Strength ◽  
Sand And Gravel ◽  
Strain Increase ◽  
Peak Value

Basing on triaxial experiments, the paper conducts the research to Cemented Sand and Gravel constitutive model. Using virtual rigid spring method, the Cemented Sand and Gravel constitutive model with considering the softening characteristics of material is established, and parameters needed are determined, the model establishes the foundation of non-linear analysis of Cemented Sand and Gravel structure. Mechanical properties and constitutive model study of Cemented Sand and Gravel is key to Cemented Sand and Gravel faced eath-rockfill dam. Basing the Mechanical properties triaxial experiment of the material, the paper gives further discussion on the constitutive model of Cemented Sand and Gravel. From the results of the triaxial test, when the cemented material content is smaller than 20kg/m3, the stress strain curve agrees quite well with hyperbolic law to which the normal gravel test curve also obeys, the exception is the increase of shearing strength. If the cemented material content is more than 30kg/m3, there is a peak value on the stress strain curve, the curve (before peak value) shows that axial strain increase with deviatoric stress with the increment gradually changing slowly, i.e. the stress strain curve has obvious nonlinear feature. the curve peaks value at the axial strain =2％, the stress strain curve present softening pattern that deviatoric stress decreases with the strain increase if continuous applying axial load. When axial strain lies between 2% and 6%, the shearing strength of samples decreases rapidly, after this interval, the shear strength tends to the stable value in the final. It is core problem the paper try to solve that how to describe Cemented Sand and Gravel constitutive model.

Deformation of Adaptive Heterophase Crystal

1994 ◽  
Vol 360 ◽  
Author(s):  
Alexander L. Roytburd ◽  
Julia Slutsker
Keyword(s):  
Strain Curve ◽  
Negative Slope ◽  
Product Phase ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Equilibrium Stress ◽  
Stress Control ◽  
Plane Parallel ◽  
Loading And Unloading ◽  
Calculated Equilibrium

AbstractA crystal which can be in two possible phase states is considered. During tensile extension the crystal is deformed elastically. After a certain amount of elastic strain a phase transformation begins. For each fixed level of strain an equilibrium mesostructure is established, which corresponds to a minimum in the free energy of the crystal. The equilibrium mesostructure consists of plane, parallel layers of a product phase separated by layers of an initial phase. The product phase itself consists of two or more different domains (twins) forming plane, parallel alternations. The volume fractions of the phases and of different twin components in the product phase are functions of strain and temperature. Above a critical temperature the product phase is a single domain (untwinned). The stress-strain curve which reflects the evolution of the equilibrium mesostructure is calculated. For deformation under a strain control the calculated equilibrium stress-strain curve has a section with negative slope that corresponds to a negative Young's modulus. If deformation proceeds under stress control, hysteretic stress-strain curves on loading and unloading will result from a section with negative slope.

Strength Characteristic of Ordovician Limestone under Unloading Condition

2014 ◽  
Vol 488-489 ◽  
pp. 329-332
Author(s):  
Xiang Min Cheng ◽  
Yu Chun Yang ◽  
Guo Bin Zhao ◽  
Zhi Yong Qu ◽  
Shu Wen Chen
Keyword(s):  
Strength Characteristic ◽  
Residual Strength ◽  
Loading Condition ◽  
Friction Angle ◽  
Peak Strength ◽  
Ordovician Limestone ◽  
Loading And Unloading

The Strength characteristic of rock are different from them under unloading condition. The Strength characteristic of Ordovician limestone under loading and unloading condition of high compress which were taken from North Tian Mountain. It indicated that : Under unloading condition cohesion c and inner friction angle decrease according to loading condition, and the residual strength has more decrease than peak strength. Under unloading, peak compress strength and residual compress strength decrease distinctly, and the decrease reduces along with confining compress increasing.

Energy Dissipation Analysis on Unloading Confining Pressure Failure Process of Rock Material

2012 ◽  
Vol 256-259 ◽  
pp. 398-401 ◽  
Author(s):  
Fu Jiang Chen ◽  
Hong Xia Li ◽  
Ze Qi Zhu
Keyword(s):  
Energy Dissipation ◽  
Rock Sample ◽  
Failure Process ◽  
Strain Curve ◽  
Confining Pressure ◽  
Rock Material ◽  
Test Machine ◽  
Lateral Deformation ◽  
Unloading Confining Pressure ◽  
Pressure Failure

The energy dissipation law of rock material are analyzed comprehensively by studying the energy exchange between test machine and rock sample in two typical stress-strain curve of unloading tests. The relationships between energy, deformation and confining pressure in unloading confining pressure failure process are expected to be found based on energy dissipation analysis. It shows that the energy dissipation is greatly related to the failure characteristic of rock material and confining pressure. Both two unloading tests show that energy dissipation has a nonlinear relationship with time and linear relationship with lateral deformation. The much the confining pressure is in unloading condition, the more the energy dissipation is under the same lateral deformation, and the obviously the rock sample suffers brittle failure.

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