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.

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 Creep damage behavior of red sandstone after high temperature

2021 ◽  
Author(s):  
Xiaokang Pan ◽  
Filippo Berto ◽  
Xiaoping Zhou
Keyword(s):  
High Temperature ◽  
Uniaxial Compression ◽  
Deformation Modulus ◽  
Creep Damage ◽  
Viscosity Coefficient ◽  
Creep Tests ◽  
Red Sandstone ◽  
Instantaneous Strain ◽  
Treated Sample ◽  
Instantaneous Deformation

This work discusses the results from tests conducted to investigate the uniaxial compression and creep behavior of red sandstone. The original untreated sample and the 800 ℃ treated sample have been selected to carry out the experiments. It has been found that high temperature has obvious influence on the mechanical properties of red sandstone. The relationship between creep strain and instantaneous strain, as well as instantaneous deformation modulus and creep viscosity coefficient have been analyzed. It has been found that high temperature reduces the ability of red sandstone to resist instantaneous deformation and creep deformation. Acoustic emission (AE) technology has been also used in the loading process of uniaxial compression and creep tests, providing a powerful means for damage evolution analysis of red sandstone.

A nonlinear creep damage model for salt rock

2018 ◽  
Vol 28 (5) ◽  
pp. 758-771 ◽  
Author(s):  
Fei Wu ◽  
Jie Chen ◽  
Quanle Zou
Keyword(s):  
Test Data ◽  
Damage Model ◽  
Creep Damage ◽  
Nonlinear Creep ◽  
Salt Rock ◽  
Creep Tests ◽  
Nonlinear Constitutive Equation ◽  
Damage Constitutive Model ◽  
Creep Damage Model ◽  
Actual Stress

In the creep tests, stress is no longer a constant and increases gradually under the influence of damage occurring during accelerating creep, which is a slow-loading process rather than a conventional creep. With the accumulation of the damage over time, the actual stress increases greatly. The increased actual stress not only generates loading strain but also causes the steady creep rate to rise. This coupling possibly explains why salt rock presents nonlinear accelerating characteristics at the accelerating creep stage. In this work, the constraint of the present creep concept was overcome by assuming that the acceleration creep phase is a coupling process of loading and creeping. Furthermore, we demonstrate that the total strain in this phase is equal to the sum of loading strain and creeping strain. A new nonlinear constitutive equation for creep was then derived, and the mechanisms underlying the nonlinear accelerating characteristics emerging at the stage of accelerating creep are further explained. A step-loading experiment on salt rock was performed for a period of six months. The characteristics of accelerating creep appeared in the last step of loading. This new nonlinear creep damage constitutive model was used to fit and analyze the test data. Obtained results show that this model fits well to these test data and also favorably represents the nonlinear characteristics of accelerating creep, thus supporting the model’s validity.

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.

Creep performance of OFP copper for the overpack of repository canisters

2006 ◽  
Vol 932 ◽  
Author(s):  
Pertti Auerkari ◽  
Stefan Holmström ◽  
Jorma Salonen ◽  
Pertti Nenonen
Keyword(s):  
Grain Boundary ◽  
Axial Stress ◽  
Creep Damage ◽  
Parent Material ◽  
Creep Model ◽  
Boundary Zone ◽  
Creep Failure ◽  
Uniaxial Creep ◽  
Notch Tip

ABSTRACTTo experimentally assess the long term creep performance of oxygen-free phosphorus- doped (OFP) copper for the overpack of repository canisters, the combination of modestly elevated temperature and multi-axial stress state has been applied for accelerated testing. Multi-axiality was induced by using notched compact tension (CT) specimens, with interrupted testing to periodically inspect for creep damage. Uniaxial creep testing was also conducted to support creep analysis of the CT specimens. After about 10000 h of testing at 150°C/46 MPa (reference stress), the inspected CT specimens showed only marginal creep cavity indications near the notch tip. However, a distinct grain boundary zone with elevated Pcontent was observed to appear and widen during testing, mainly near the notch tip. The significance of the grain boundary zone is not well understood, but indicates stress-enhanced microstructural changes at relatively low temperatures. The predicted isothermal uniaxial creep life at 150°C/46 MPa agreed satisfactorily within a factor of two in time, when obtained independently from converted multi-axial testing results and directly from a creep model based on the available uniaxial data. Although the uncertainties in extended extrapolation remain large, the prediction would suggest safe long term service at leastagainst pure creep failure of intact parent material.

Research of Inclination Angle Effect on Joint Rock Macromechanical Parameters

2011 ◽  
Vol 704-705 ◽  
pp. 1089-1094
Author(s):  
Yan Feng Feng ◽  
Tian Hong Yang ◽  
Hua Wei ◽  
Hua Guo Gao ◽  
Zhe Zhang
Keyword(s):  
Rock Mass ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Damage Mechanics ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Uniaxial Compression Test ◽  
Joint Rock Mass ◽  
Test Result ◽  
Joint Rock

The joint of rock mass influences and controls the rock mass intensity, deformation characteristics and instability failure in the rock engineering to a great extent. Using the similar material simulation is of different inclination angle of non-penetration jointing and non-jointing rock mass, through using rigid servo compression machine to carry uniaxial compression test, we get a nearly same trend of joint rock mass stress-strain curve of different angle, the curve of inclination angle of 45 is analyzed, the test result shows that the compressive strength first decreases and then increases gradually with the increase of rock inclination angle. The compression intensity is its minimum when of the inclination angle of 45°, and the deformation modulus first decreases and then increases, but deformation modulus of 30° is its minimum. In addition, through the use of developed RFPA2D system to simulate on trial uniaxial compression value based on microscopic damage mechanics, we get the conclusion that the numerical analysis and test result is fitting approximately, it is validated that the numerical model can simulate joint rock well. Keywords: joint rock mass, inclination angle, uniaxial compression, compressive intensity, deformation modulus

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.

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.

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