scholarly journals Uniaxial Compression Behavior of Cement Mortar and Its Damage-Constitutive Model Based on Energy Theory

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1309 ◽  
Author(s):  
Yunliang Tan ◽  
Qingheng Gu ◽  
Jianguo Ning ◽  
Xuesheng Liu ◽  
Zhichuang Jia ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Uniaxial Compression ◽  
Loading Rate ◽  
Cement Mortar ◽  
Axial Stress ◽  
Great Influence ◽  
Strain Curve ◽  
Compression Tests ◽  
Whole Process ◽  
Damage Constitutive Model

The mechanical properties of mortar materials in construction are influenced both by their own proportions and external loads. The trend of the stress–strain curve in cracks compaction stage has great influence on the relationship between the strength and deformation of cement mortar. Uniaxial compression tests of mortar specimens with different cement–sand ratios and loading rates were carried out, and the stored and dissipated energies were calculated. Results indicated that the elastic modulus and strength of mortar specimens increase with the cement–sand ratio and loading rate. The energy dissipation shows good consistency with the damage evolution. When the loading rate is less than 1.0 mm/min, most of the constitutive energy at the peak point is stored in the specimen and it increase with cement–sand ratio. A simple representation method of axial stress in cracks compaction stage was proposed and an energy-based damage constitutive model—which can describe well the whole process of cement mortar under uniaxial compression—was developed and verified.

scholarly journals A Thermal Damage Constitutive Model for Oil Shale Based on Weibull Statistical Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Guijie Zhao ◽  
Chen Chen ◽  
Huan Yan
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Oil Shale ◽  
Thermal Damage ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Practical Significance ◽  
Compression Tests ◽  
Different Temperatures ◽  
Damage Constitutive Model

In this work, we first studied the thermal damage to typical rocks, assuming that the strength of thermally damaged rock microelements obeys a Weibull distribution and considering the influence of temperature on rock mechanical parameters; under the condition that microelement failure conforms to the Drucker–Prager criterion, the statistical thermal damage constitutive model of rocks after high-temperature exposure was established. On this basis, conventional triaxial compression tests were carried out on oil shale specimens heated to different temperatures, and according to the results of these tests, the relationship between the temperature and parameters in the statistical thermal damage constitutive model was determined, and the thermal damage constitutive model for oil shale was established. The results show that the thermal damage in oil shale increases with the increase of temperature; the damage variable is largest at 700°C, reaching 0.636; from room temperature to 700°C, the elastic modulus and Poisson’s ratio decrease by 62.66% and 64.57%, respectively; the theoretical stress-strain curve obtained from the model is in good agreement with the measured curves; the maximum difference between the two curves before peak strength is only 5 × 10−4; the model accurately reflects the deformation characteristics of oil shale at high temperature. The research results are of practical significance to the underground in situ thermal processing of oil shale.

scholarly journals Study of Damage Constitutive Model of Brittle Rocks considering Stress Dropping Characteristics

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Fei Li ◽  
Shuang You ◽  
Hongguang Ji ◽  
Hao Wang
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Brittle Rock ◽  
Model Parameters ◽  
Deformation And Failure ◽  
Brittle Rocks ◽  
Whole Process ◽  
Confining Pressures ◽  
Damage Constitutive Model

Deep brittle rock exhibits characteristics of rapid stress dropping rate and large stress dropping degree after peak failure. To simulate the whole process of deformation and failure of the deep brittle rock under load, the Lemaitre strain equivalent theory is modified to make the damaged part of the rock has residual stress. Based on the damage constitutive model considering residual strength characteristics, a correction factor reflecting stress dropping rate is added, the Weibull distribution is used to describe the inhomogeneity of rock materials, and Drucker–Prager criterion is used to quantitatively describe the influence of stress on damage; a damage constitutive model of deep brittle rock considering stress dropping characteristics is established. According to the geometric features of the rock stress-strain curve, the theoretical expressions of model parameters are derived. To verify the rationality of the model, triaxial compression experiments of deep brittle rock under different confining pressures are conducted. And the influence of model parameters on rock mechanical behaviour is analysed. The results show that the model reflects the stress dropping characteristics of deep brittle rock and the theoretical curve is in good agreement with the experimental results, which indicates that the proposed constitutive model is scientific and feasible.

scholarly journals Damage Strengthening Constitutive Model of Cemented Paste Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Kangli Cheng ◽  
Bingbing Tu ◽  
Lang Liu ◽  
Bo Zhang ◽  
Huafu Qiu
Keyword(s):  
Constitutive Model ◽  
Uniaxial Compression ◽  
Strain Curve ◽  
Cemented Paste Backfill ◽  
Test Results ◽  
Stress Strain ◽  
Filling Materials ◽  
Paste Backfill ◽  
Damage Constitutive Model ◽  
Ucs Test

In order to consider the influence of mesoscopic characteristics of materials on the constitutive model of cemented paste backfill (CPB), the uniaxial compression variables and the damage constitutive model, considering the influence of porosity and pore size of filling materials, were derived based on the strain equivalence principle and Weibull probability distribution function. The nuclear magnetic resonance (NMR) tests and unconfined compression strength (UCS) tests were carried out on 8 groups of CPB specimens with different slurry concentrations and cement-tailings ratios. Then, the expression of damage strengthening coefficient is determined, and the stress-strain curves measured by the theoretical model were compared with the experimental ones. The results show that the uniaxial compression constitutive model proposed is in good agreement with UCS test results and can effectively describe the damage evolution law and the development process of stress-strain curve of CPB under uniaxial compression. The 28-day compressive strength of CPB can reach 8 MPa, the residual strength is about 1∼2 MPa, the elastic modulus is about 200∼2000 MPa, and the porosity is about 3∼5%. The CPB with slurry concentration of 74% and 76% and cement-tailings ratio of 1 : 4 and 1 : 6 is more reasonable, and the relevant mechanical parameters are more stable.

Creep properties and damage constitutive model of salt rock under uniaxial compression

2019 ◽  
Vol 29 (6) ◽  
pp. 902-922 ◽  
Author(s):  
Junbao Wang ◽  
Qiang Zhang ◽  
Zhanping Song ◽  
Yuwei Zhang
Keyword(s):  
Uniaxial Compression ◽  
Axial Stress ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Creep Damage ◽  
Salt Rock ◽  
Steady Creep ◽  
Creep Failure ◽  
Compression Creep ◽  
Damage Constitutive Model

To study the creep property of salt rock, uniaxial compression creep tests on salt rock specimens were carried out. The test results indicate that there is no steady creep of the salt rock used in this test in a strict sense. Even in the steady creep stage, the creep rate of salt rock changes continuously over time, but with a relatively smaller change range. When the axial stress does not exceed 9.5 MPa, the isochronous stress–strain curve of salt rock is approximately straight. While the axial stress exceeds 9.5 MPa, the isochronous stress–strain curve deflects to the strain axis, and the larger the axial stress, the more obvious the deflection. Thus, the long-term strength of the salt rock used in this test can be determined as 9.5 MPa. A mathematical expression for predicting the creep failure time of rock is proposed on the basis of assuming the change rule of rock strength over time conforms to the Usher function. Then starting from the variation in deformation modulus with respect to time in the creep process of salt rock, the elastic modulus of the damaged rock material is characterized by the deformation modulus, and the creep damage evolution equation of rock is established. Combined with the continuous damage mechanics theory, a new creep damage constitutive model for rock is proposed. The rationality of the model is verified using the uniaxial compression creep test results of salt rock. The results show that the new model can not only describe the attenuation and the steady creep of salt rock under low stress level, but also reflect the whole creep failure process under high stress level. The predicted curves under different axial stresses are all in good agreement with the test data.

Mechanical properties and damage constitutive model for uniaxial compression of salt rock at different loading rates

2021 ◽  
pp. 105678952098386
Author(s):  
Junbao Wang ◽  
Qiang Zhang ◽  
Zhanping Song ◽  
Yuwei Zhang ◽  
Xinrong Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Loading Rate ◽  
Peak Stress ◽  
Test Results ◽  
Salt Rock ◽  
Loading Rates ◽  
Damage Constitutive Model ◽  
Rock Specimens

To study the effect of loading rate on the mechanical properties of salt rock, uniaxial compression tests and acoustic emission tests at different loading rates were carried out on salt rock specimens. The test results show that with increases in loading rate, the peak stress of salt rock increases first and then essentially remains unchanged, and the elastic modulus increases gradually, while the strain at peak stress decreases gradually. Moreover, the Poisson’s ratio is independent of loading rate. The macroscopic failure modes of the salt rock specimens at different loading rates are all ‘X’-type conjugate shear failure. However, the loading rate is closely related to the degree of fracture, such that the smaller the loading rate is, the higher is the degree of fracture of salt rock. In order to describe the stress–strain behaviour in the process of salt rock failure, a damage variable expression represented by the deformation modulus was proposed, and a rock damage constitutive model was established according to the theory of continuum damage mechanics. The rationality of the damage constitutive model was verified by using the present uniaxial compression test results of salt rock and existing test data from the literature. The results show that the model can accurately describe the stress–strain response of rock in the failure process.

Application of a Creep Damage Constitutive Model for the Rotor of a 1000 MW Ultra-Supercritical Steam Turbine

2015 ◽  
Author(s):  
Jishen Jiang ◽  
Weizhe Wang ◽  
Nailong Zhao ◽  
Peng Wang ◽  
Yingzheng Liu ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Steam Turbine ◽  
Axial Stress ◽  
Creep Damage ◽  
Turbine Rotor ◽  
Creep Analysis ◽  
Wide Range ◽  
Damage Constitutive Model ◽  
Creep Constitutive Model ◽  
Basic Features

A damage-based creep constitutive model for a wide stress range is applied to the creep analysis of a 1000 MW ultra-supercritical steam turbine, the inlet steam of which reaches 600°C and 35 MPa. In this model, the effect of complex multi-axial stress and the nonlinear evolution of damage are considered. To this end, the model was implemented into the commercial software ABAQUS using a user-defined material subroutine code. The temperature dependent material constants were identified from the experimental data of advanced heat resistant steels using curve fitting approaches. A comparison of the simulated and the measured results showed that they reached an acceptable agreement. The results of the creep analysis illustrated that the proposed approach explains the basic features of stress redistribution and the damage evolution in the steam turbine rotor over a wide range of stresses and temperatures.

Heterogeneous Lattice Model Based Simulation of Concrete under Uniaxial Loading

2015 ◽  
Vol 784 ◽  
pp. 249-257
Author(s):  
Xiao Huan Yan ◽  
Xiao Dan Ren ◽  
Jie Li
Keyword(s):  
Constitutive Model ◽  
Uniaxial Tension ◽  
Uniaxial Compression ◽  
Lattice Model ◽  
Random Medium ◽  
Uniaxial Loading ◽  
Model Based ◽  
Damage Constitutive Model ◽  
Stochastic Damage ◽  
Heterogeneous Lattice

The heterogeneous lattice model is presented to simulate the behaviors of concrete, in which the concrete is regarded as random medium and the stochastic damage constitutive model is proposed. The parameters of the stochastic damage constitutive is identified compared with the experiment results of concrete under uniaxial tension and uniaxial compression.

scholarly journals A Damage Constitutive Model of Rock Subjected to Freeze-Thaw Cycles Based on Lognormal Distribution

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Hang Lin ◽  
Linyuan Liang ◽  
Yifan Chen ◽  
Rihong Cao
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Lognormal Distribution ◽  
Constitutive Models ◽  
Strain Curve ◽  
Statistical Distribution ◽  
Freeze Thaw ◽  
Accurate Quantitative Analysis ◽  
Distribution Parameters ◽  
Damage Constitutive Model

The constitutive model of rock is closely connected with the mechanical properties of rock. To achieve a more accurate quantitative analysis of the mechanical properties of rock after the action of freeze-thaw cycles, it is necessary to establish the constitutive models of rock subjected to freeze-thaw cycles from the view of rock damage. Based on the assumption of rock couple damage, this study established a statistical damage constitutive model of rock subjected to freeze-thaw cycles by combining the lognormal distribution, which is commonly used in engineering reliability analysis, and the strain strength theory. Then, the coordinates and derivative at the peak of the stress-strain curve of the rock after the action of freeze-thaw cycles were obtained through experiments to solve the statistical distribution parameters με and S of the model, whereafter, the theoretical curves by the established model were compared with the experimental curves to verify the validity of it, which shows a great agreement. Finally, the sensitivity analysis of the statistical distribution parameters was implemented. The results indicate that με reflects the strength of the rock, which shows a positive relation, and S stands for the brittleness of the rock, which shows a negative relation.

scholarly journals Physical and Mechanical Properties Evolution of Coal Subjected to Salty Solution and a Damage Constitutive Model under Uniaxial Compression

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3264
Author(s):  
Min Wang ◽  
Qifeng Guo ◽  
Yakun Tian ◽  
Bing Dai
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Immersion Time ◽  
Physical And Mechanical Properties ◽  
Relative Mass ◽  
Stress Strain ◽  
Damage Constitutive Model ◽  
Underground Reservoirs

Many underground reservoirs for storing water have been constructed in China’s western coal mines to protect water resources. Coal pillars which work as dams are subjected to a long-term soaking environment of concentrated salty water. Deterioration of the coal dam under the attack of the salty solution poses challenges for the long-term stability and serviceability of underground reservoirs. The evolution of the physical and mechanical properties of coal subjected to salty solutions are investigated in this paper. Coal from a western China mine is made to standard cylinder samples. The salty solution is prepared according to chemical tests of water in the mine. The coal samples soaked in the salty solution for different periods are tested by scanning electron microscope, nuclear magnetic resonance, and ultrasonic detector techniques. Further, uniaxial compression tests are carried out on the coal specimens. The evolutions of porosity, mass, microstructures of coal, solution pH values, and stress–strain curves are obtained for different soaking times. Moreover, a damage constitutive model for the coal samples is developed by introducing a chemical-stress coupling damage variable. The result shows that the corrosion effect of salty solution on coal samples becomes stronger with increasing immersion time. The degree of deterioration of the longitudinal wave velocity (vp) is positively correlated with the immersion time. With the increase in soaking times, the porosity of coal gradually increases. The relative mass firstly displays an increasing trend and then decreases with time. The peak strength and elastic modulus of coal decreases exponentially with soaking times. The developed damage constitutive model can well describe the stress–strain behavior of coal subjected to salty solution under the uniaxial compression.

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