Uniaxial compression mechanical properties and damage constitutive model of limestone under osmotic pressure

To study the influence of osmotic pressure on the uniaxial compression mechanical properties of limestone, uniaxial compression tests were carried out on limestone specimens under different osmotic water pressure. The test results show that with the increase of osmotic pressure, the closure strain, yield strain and peak strain of limestone gradually increase, while the closure stress, yield stress, peak stress and elastic modulus gradually decrease. To describe the stress-strain response of limestone during uniaxial compression failure, the concepts of compaction factor and osmotic pressure influencing factor were proposed, and a constitutive model of rock compaction stage was established by integrating the relationship between the compaction factor and osmotic pressure influencing factor and the tangent modulus of compaction section. On this basis, combining the continuum damage mechanics theory, and assuming that the rock micro-unit strength obeys the compound power function distribution, a constitutive model reflecting the uniaxial compression mechanical properties of rock under osmotic pressure was established by the statistical method. The rationality of the model was verified using the results of the uniaxial compression test of limestone under different osmotic pressures. The results show that the test results under different osmotic pressures are in good agreement with the theoretical curves, and the model in this paper can reflect the stress-strain response of limestone before its failure under different osmotic pressures.

Download Full-text

Uniaxial Mechanical Properties of Sandstone under Cyclic of Drying and Wetting

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.2310 ◽

2011 ◽

Vol 243-249 ◽

pp. 2310-2313 ◽

Cited By ~ 5

Author(s):

Hua Yan Yao ◽

Zhen Hua Zhang ◽

Zhao Hui Zhu

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Young’S Modulus ◽

Young's Modulus ◽

Test Results ◽

Stress Strain ◽

Deformation And Failure ◽

Deformation Behaviors ◽

Uniaxial Strength

Water is an important factor that influences the mechanical properties of rock. Uniaxial compressive experiments have been carried out on sandstone under different cyclic times of drying and wetting. The corresponding complete stress-strain curves are obtained, and characteristics of deformation and failure are analyzed. Test results show that when sandstone samples are submitted to cyclic of drying and wetting, the uniaxial strength and Young's modulus of sandstone obviously decrease. Then, the improved Duncan constitutive model is developed, which can do better in describing sample’s deformation behaviors subject to different cyclic times of drying and wetting. Introduction

Download Full-text

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

Mathematics ◽

10.3390/math9243264 ◽

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.

Download Full-text

Uniaxial Compression Fractal Damage Constitutive Model of Rock Subjected to Freezing and Thawing

Periodica Polytechnica Civil Engineering ◽

10.3311/ppci.15313 ◽

2020 ◽

Author(s):

Shengtao Zhou ◽

Nan Jiang ◽

Xuedong Luo ◽

Wen Fang ◽

Xu He

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Uniaxial Compression ◽

Residual Strength ◽

Structural Damage ◽

Compression Fracture ◽

Peak Strain ◽

Freeze Thaw ◽

Deformation Stage ◽

Damage Constitutive Model

Mechanical properties of the rock in the cold regions are often affected by freeze-thaw cycles and loads. It is of great theoretical significance and engineering value to establish a uniaxial compression damage constitutive model of the rock under freeze-thaw cycles that can reflect the relationship between macroscopic and mesoscopic structural damage. In this paper, macroscopic and mesoscopic methods are combined with statistical methods to quantitatively analyze the damage degree of rock under freeze-thaw cycles and loads. Combined with the fractal features of the macroscopic image of the section, a fractal damage constitutive model considering the residual strength of rock is established. In addition, the model is subsequently verified by the experiment. The experiment shows that the mechanical properties of rocks subjected to freeze-thaw cycles and loads are determined by freeze-thaw damage variables, load damage variables, and their coupling effects. As the number of freeze-thaw cycles increases, the uniaxial compressive strength and elastic modulus of rocks decrease, and peak strain increases. By using the fractal dimension of the compression fracture surface as a bridge considering the residual strength of the rock, the constitutive model can better reflect the compaction stage, elastic deformation stage and plastic deformation stage of the uniaxial compression process of the freeze-thaw rocks.

Download Full-text

Damage Strengthening Constitutive Model of Cemented Paste Backfill

Advances in Civil Engineering ◽

10.1155/2021/5593983 ◽

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.

Download Full-text

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

International Journal of Damage Mechanics ◽

10.1177/1056789520983868 ◽

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.

Download Full-text

Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Micromachines ◽

10.3390/mi12050529 ◽

2021 ◽

Vol 12 (5) ◽

pp. 529

Author(s):

Chunzhi Du ◽

Zhifan Li ◽

Bingfei Liu

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Shape Memory ◽

Young’S Modulus ◽

Residual Strain ◽

Surface Effect ◽

Young's Modulus ◽

Strain Curve ◽

Stress Strain ◽

Strength Limit

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

Download Full-text

Predicting the Mechanical Properties of Bimrocks with High Rock Block Proportions Based on Resonance Testing Technology and Damage Theory

Applied Sciences ◽

10.3390/app9173537 ◽

2019 ◽

Vol 9 (17) ◽

pp. 3537

Author(s):

Yuexiang Lin ◽

Limin Peng ◽

Mingfeng Lei ◽

Xiang Wang ◽

Chengyong Cao

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Constitutive Model ◽

Uniaxial Compression ◽

Rock Block ◽

Dynamic Elastic Modulus ◽

Parameter Determination ◽

Design Parameters ◽

Damage Theory ◽

Design And Construction

Block-in-matrix-rocks (bimrocks) are very complicated geological masses that cause many challenging problems during the design and construction of engineering projects, such as parameter determination and landsliding. Successful engineering design and construction depends on a suitable constitutive model and reliable design parameters for geological masses. In this paper, the vibration attenuation signal of welded bimrocks was obtained and studied using resonance test technology. Combined with a uniaxial compression test, a constitutive model was proposed to describe the mechanical behavior of welded bimrocks. On this basis, the relations between the dynamic elastic modulus and the physical parameters of bimrocks were established, which included macroscopic mechanical parameters and damage constitutive parameters. Consequently, a new technological process was proposed to provide quick identification of the mechanical properties of welded bimrocks. The results indicate that the dynamic elastic modulus is highly correlated with the rock block proportion (RBP) and uniaxial compression strength (UCS). It is an effective parameter to predict the strength of the bimrocks with high RBPs. Additionally, the proposed constitutive model, which is based on damage theory, can accurately simulate the strain softening behavior of the bimrocks. Combining the resonant frequency technology and the proposed constitutive model, the complete stress strain curve can be obtained in a rapid and accurate manner, which provides a further guarantee of the stability and safety of underground engineering.

Download Full-text

Study on Dynamic Mechanical Properties and Constitutive Model Construction of TC18 Titanium Alloy

Metals ◽

10.3390/met10010044 ◽

2019 ◽

Vol 10 (1) ◽

pp. 44 ◽

Cited By ~ 2

Author(s):

Changming Zhang ◽

Anle Mu ◽

Yun Wang ◽

Hui Zhang

Keyword(s):

Mechanical Properties ◽

Titanium Alloy ◽

Flow Stress ◽

Yield Strength ◽

Constitutive Model ◽

Testing Machine ◽

Dynamic Mechanical Properties ◽

Stress Strain ◽

Dynamic Mechanical ◽

Different Temperatures

In order to investigate the static and dynamic mechanical properties of TC18 titanium alloy, the quasi-static stress–strain curve of TC18 titanium alloy under room temperature was obtained by DNS 100 electronic universal testing machine (Changchun Institute of Mechanical Science Co., Ltd., Changchun, China). Meanwhile, the flow stress–strain curves under different temperatures and strain rates are analyzed by split Hopkinson pressure bar (SHPB) device with synchronous assembly system. On the basis of the two experimental data, the JC constitutive model under the combined action of high temperature and impact load is established using the linear least squares method. The results show the following: the yield strength and flow stress of TC18 titanium alloy increase slowly with the increase of the strain rate, and the strain value corresponding to the yield strength is reduced. With the increase of strain, the flow stress increases at first and then decreases at different temperatures. The strain value corresponding to the transition point rises with the temperature increase, and the corresponding stress value remains basically unchanged. With the increase of experimental temperature, the flow stress shows a downward trend, and the JC constitutive model can predict the plastic flow stress well.

Download Full-text

A new elastoplastic constitutive model for coarse granular aggregates incorporating particle breakage

Canadian Geotechnical Journal ◽

10.1139/t04-025 ◽

2004 ◽

Vol 41 (4) ◽

pp. 657-671 ◽

Cited By ~ 115

Author(s):

Wadud Salim ◽

Buddhima Indraratna

Keyword(s):

Constitutive Model ◽

Plastic Flow ◽

Current Model ◽

Particle Breakage ◽

Flow Rule ◽

Peak Strain ◽

Stress Strain ◽

Coarse Aggregates ◽

Stress Changes ◽

Plastic Flow Rule

A new elastoplastic stressstrain constitutive model is developed for granular coarse aggregates incorporating the degradation of particles during triaxial shearing. Coarse granular aggregates are subjected to breakage during excessive stress changes. Most of the available constitutive models do not consider the degradation of particles during shearing. In the current model, a plastic flow rule has been developed incorporating the energy consumption due to particle breakage during shear deformation. A non-associated flow and a kinematic type yield locus have been adopted in the model. A general formulation for the rate of particle breakage during shearing has been developed and incorporated in the plastic flow rule. The effects of particle breakage on the plastic distortional and volumetric deformations are incorporated in the current model. The stressstrain formulations are developed within the general critical state framework. The model can accurately predict the stressstrain and volume change behaviour of coarse granular aggregates. The plastic dilation and contraction features of coarse aggregates at various confining pressures are well captured, and the strain-hardening and post-peak strain-softening behaviour of coarse granular media is adequately represented. A particular feature of the model is its capability to predict the degree of particle breakage at any stage of shear deformation.Key words: constitutive modelling, coarse granular aggregates, particle breakage, dilatancy, non-associated flow, plasticity.

Download Full-text