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.

scholarly journals High-Temperature Tensile and Creep Behavior in a CrMoV Steel and Weld Metal

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 109
Author(s):  
Yan Song ◽  
Mengyu Chai ◽  
Zelin Han ◽  
Pan Liu
Keyword(s):  
High Temperature ◽  
Weld Metal ◽  
Creep Damage ◽  
Uniaxial Tensile ◽  
Second Phase ◽  
Creep Tests ◽  
Damage Mechanisms ◽  
Integrity Assessment ◽  
Steel Weldment ◽  
High Temperature Tensile

The 2.25Cr1Mo0.25V steel is a vanadium-modified 2.25Cr1Mo steel and is being widely used in the manufacture of heavy-wall hydrogenation reactors in petrochemical plants. However, the harsh service environment requires a thorough understanding of high-temperature tensile and creep behaviors of 2.25Cr1Mo0.25V steel and its weld for ensuring the safety and reliability of hydrogenation reactors. In this work, the high-temperature tensile and creep behaviors of base metal (BM) and weld metal (WM) in a 2.25Cr1Mo0.25V steel weldment used for a hydrogenation reactor were studied experimentally, paying special attention to its service temperature range of 350–500 °C. The uniaxial tensile tests under different temperatures show that the WM has higher strength and lower ductility than those of BM, due to the finer grain size in the WM. At the same time, the short-term creep tests at 550 °C reveal that the WM has a higher creep resistance than that of BM. Moreover, the creep damage mechanisms were clarified by observing the fracture surface and microstructures of crept specimens with the aid of scanning electron microscopy (SEM). The results showed that the creep damage mechanisms of both BM and WM are the initiation and growth of creep cavities at the second phase particles. Results from this work indicate that the mismatch in the high-temperature tensile strength, ductility, and creep deformation rate in 2.25Cr1Mo0.25V steel weldment needs to be considered for the design and integrity assessment of hydrogenation reactors.

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 The Uniaxial Creep Characteristics of Red Sandstone under Dry-Wet Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Guangcheng Liu ◽  
Xin Huang ◽  
Jianyong Pang
Keyword(s):  
Elastic Modulus ◽  
Creep Strain ◽  
Failure Modes ◽  
Peak Strength ◽  
Logarithmic Function ◽  
Creep Tests ◽  
Engineering Structures ◽  
Red Sandstone ◽  
Instantaneous Strain

Water is one of the most important factors that affect the long-term stability of geotechnical engineering structures. Rainfall often results in periodic changes in the water content in underground rock, which is subjected to alternating dry-wet cycles. In this paper, in order to study the short-term and long-term mechanical properties of red sandstone under these dry-wet cycles, a series of uniaxial compressive strength (UCS) tests and multistage creep tests have been carried out on specimens of red sandstone after being treated to different numbers of dry-wet cycles. A scanning electron microscope (SEM) was used to image the different groups of specimens. The test results have shown that the peak strength and the elastic modulus of the red sandstone decreased as the number of dry-wet cycles increased. It is worth noting that the first immersion of the specimens decreased their strength the most, and the negative logarithmic function was able to better reflect the peak strength of the red sandstone and the variation of its elastic modulus in relation to the number of dry-wet cycles. The results of the creep tests have shown that the instantaneous strain and creep strain of the sandstone increased significantly with the increase of the number of dry-wet cycles. A linear function and a negative logarithmic function can be used to describe the instantaneous strain and the creep strain, respectively. The creep duration of the red sandstone in its failure stage decreased with the increase of the number of dry-wet cycles, and the creep rate increased with the increase of the number of dry-wet cycles. Lastly, the failure modes of the red sandstone were observed; the results showed that the angle between the main crack and the axis of creep failure gradually increased with the increase of the number of dry-wet cycles and the angle of the internal friction and the cohesion decreased. In addition, the failure mode of the specimens changed from tensile failure to shear failure. The microstructure of the sandstone showed that the surface of the specimen changed from being compact to being loose, and the mineral particles in the specimen changed from being spherical to being flat and curly; this led to a decrease in the macroscopic mechanical parameters of the sandstone.

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.

Creep Properties and Damage Study of Ni-Based Alloy C276 at High Temperature

2011 ◽  
Vol 328-330 ◽  
pp. 1143-1148 ◽  
Author(s):  
Xue Ping Mao ◽  
Qi Guo ◽  
Sheng Yuan Zhang ◽  
Su Yang Hu ◽  
Dao Gang Lu ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress Level ◽  
Creep Damage ◽  
Primary Creep ◽  
Type I ◽  
High Temperature Creep ◽  
Fuel Cladding ◽  
Creep Tests ◽  
Temperature Creep ◽  
Creep Characteristic

One of the two challenges about Supercritical Water-Cooled Reactor is material, especially for the fuel cladding. High temperature creep tests of Ni-based alloy C276, one of the candidate materials for the fuel cladding, were carried out at 650°C~750°C, with stress 130MPa~430MPa. The effects of temperature and stress on creep were investigated, the change laws of steady state creep rate with stress and time to rupture were analysed, and creep damage factors were separately calculated based on Kachanov’s formula and Norton’s formula. The results indicate that there exist two types of primary creep characteristics in C276: Type I creep characteristic at lower stress level and Type II at higher stress level respectively. C276 shows excellent high temperature creep resistance, and Kachanov’s damage factors D vs normalized time are basically coincident at 650°C, 700°C and 750°C. The damage obtained by Norton’s formula starts at about 40% of lifetime, and the damage factors calculated by Kachanov’s formula are relatively conservative.

scholarly journals Investigation of creep damage mechanical behaviors of red sandstone considering temperature effect

2021 ◽  
Author(s):  
Xiaokang Pan ◽  
Filippo Berto ◽  
Xiaoping Zhou
Keyword(s):  
Uniaxial Compression ◽  
Failure Modes ◽  
Critical Index ◽  
Creep Damage ◽  
Uniaxial Compression Test ◽  
Mechanical Behaviors ◽  
Absolute Value ◽  
Red Sandstone ◽  
Loading Ratio ◽  
The Absolute

This work investigates the influence of temperature on the creep damage behaviors of red sandstone. The samples treated at 25 ℃, 200 ℃, 400 ℃ and 600 ℃ are selected to carry out the uniaxial compression and creep experiments. It is found that temperature has obvious influence on uniaxial compressive strength, Young’s modulus and failure modes of red sandstone. It can be also believed that the temperature can degrade the mechanical behaviors of red sandstone. However, as the temperature increases, the damage value does not always increase, the damage variable has a negative value at 25 ~ 400 ℃. It can be found that the higher the temperature, the larger the effect of loading ratio on the ratio of creep strain to instantaneous strain, that is, temperature reduces the ability of red sandstone to resist creep deformation. Acoustic emission (AE) technology has been also used in the loading process of uniaxial compression and creep tests. It is found that the probability density of AE absolute energy of different samples still satisfies the Gutenberg-Richter law well. In uniaxial compression test, as the temperature increases, the absolute value of the critical index increases exponentially. In the uniaxial creep test, as the loading ratio increases, the absolute value of the critical index first decreases and then increases. When the loading ratio is the same, as the temperature increases, the absolute value of the critical index also increases exponentially.

Modeling the Creep Damage of P91 Steel Using Peridynamics

2019 ◽  
Author(s):  
Shank S. Kulkarni ◽  
Alireza Tabarraei ◽  
Xiaonan Wang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Structural Integrity ◽  
Creep Damage ◽  
Creep Model ◽  
Creep Tests ◽  
P91 Steel ◽  
Damage Models ◽  
Modeling Creep ◽  
Non Local

Abstract Creep is an important failure mechanism of metal components working at a high temperature. To ensure the structural integrity and safety of systems working at high temperature it is essential to predict failure due to creep. Classical continuum based damage models are used widely for modeling creep damage. A more recently developed non-local mechanics formulation called peridynamics has displayed better performance in modeling damage with respect to classical local mechanics methods. In this paper, the peridynamic formulation is extended to model creep in metals. We have chosen Liu-Murakami creep model for developing a peridynamic formulation for modeling creep. The proposed formulation is validated by simulating creep tests for P91 steel and comparing the results with experimental data from the literature.

Creep Properties and Interfacial Microstructure of SiC Whisker Reinforced Si3N4

1989 ◽  
Vol 170 ◽  
Author(s):  
Håkan A. Swan ◽  
Colette O'meara
Keyword(s):  
High Temperature ◽  
Creep Resistance ◽  
Interfacial Microstructure ◽  
Deformation Mechanisms ◽  
Amorphous Films ◽  
Creep Tests ◽  
Creep Properties ◽  
High Temperature Exposure ◽  
Temperature Exposure

AbstractPreliminary creep tests were performed on SiC whisker reinforced and matrix Si3N4 material fabricated by the NPS technique. The material was extensively crystallised in the as received material, leaving only thin amorphous films surrounding the grains. No improvement in the creep resistance could be detected for the whisker reinforced material. The deformation mechanisms were found to be that of cavitation in the form of microcracks, predominantly at the whisker/matrix interfaces, and the formation of larger cracks. Extensive oxidation of the samples, as a result of high temperature exposure to air, was observed for the materials tested at 1375°C.

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