Artykuły w czasopismach: „Creep”

1

Williams, M., D. Menon i A. M. Prasad. "Flexural creep in plain concrete: State of the Art". Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, nr 1 (19.12.2022): 341–45. http://dx.doi.org/10.38208/acp.v1.519.

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Concrete, being a viscoelastic material, creeps with time causing additional strains and deflections in flexural members. Most of the studies in creep of concrete are based on long-term tests on plain concrete standard cylinders under axial compression, very limited studies have been reported on creep of concrete in flexure and direct tension. Whether the mechanism of creep in tension is different from creep in compression is still being debated. Numerous studies have been reported in the literature showing varied results with regard to the effects of creep in direct compression, direct tension and flexure. This paper provides a brief review of various creep tests on plain concrete reported and attempts to understand the effects of various parameters on the creep behaviour of concrete. Some studies reported that the creep in tension is higher than that in compression, whereas a few others obtained contradictory results from creep tests. This may be attributed to the fact that the relative creep behaviour in tension and compression is highly sensitive to the material composition, exposure conditions and loading level. The studies by various researchers on flexural creep in plain concrete are also discussed.

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2

Widjaja, Sujanto, Karl Jakus, Revti Atri, John E. Ritter i Sandeepan Bhattacharya. "Residual surface stress by localized contact-creep". Journal of Materials Research 12, nr 1 (styczeń 1997): 210–17. http://dx.doi.org/10.1557/jmr.1997.0028.

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When a ceramic material creeps under a localized stress and then cools under load, a portion of the creep flow stress is retained as a residual compressive stress due to elastic rebound being constrained by the creep zone. Localized contact-creep was used to generate residual compressive surface stress in soda-lime glass and two sintered aluminas. The Vickers indentation technique was used to measure the residual stress within the contact-creep area. Alumina with a higher elastic modulus than glass retained higher residual compressive surface stress. The results were in reasonable agreement with the predicted stress distribution given by finite element analysis.

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3

Menaya, Carmen M., P. R. English, S. A. Edwards, O. MacPherson, J. A. Roden, A. M. Robertson i J. M. Vidal. "Evaluation of a simple adaptation to a farrowing pen designed to increase the comfort level of piglets in the narrow creep in the first 48 hours of life". Proceedings of the British Society of Animal Production (1972) 1991 (marzec 1991): 62. http://dx.doi.org/10.1017/s0308229600020122.

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In commercial farrowing pens, creep areas for the piglets are often provided only at the front or on one side of the pen. Because of the strong bonding which newborn piglets have to the udder, such arrangements are often inadequate to attract piglets into the creep area where danger from hypothermia increase the suitability for the newborn piglet of farrowing pens with a typical commercial side creep design.The experiment was carried out in a commercial farrowing house with partially slatted, unbedded pens. These pens were of typical commercial ‘side creep’ design with a wide creep area on one side of the crate, and a narrow unheated area on the other. The wide creep area contained a tray with a bedding of shavings and was heated by a heat lamp. Experimental pens were adapted by placing diagonally the pen division separating the narrow creeps in two adjacent pens. This created a wider area at the front of one pen and at the rear of the adjacent pen (Fig 1). These areas were provided with a bedding of shavings and a heat lamp for the first 48 hours of life.

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Dan, Zhenhua, Jiafei Lu, Hui Chang, Ping Qu, Aifeng Zhang, Zhigang Fang, Yuecheng Dong, Ying Wang i Lian Zhou. "High-Stress Compressive Creep Behavior of Ti-6Al-4V ELI Alloys with Different Microstructures". MATEC Web of Conferences 321 (2020): 11007. http://dx.doi.org/10.1051/matecconf/202032111007.

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Influence of initial microstructure of Ti-6Al-4V ELI alloys on their compressive creep behavior at ambient temperature was investigated with applying compression stresses from 695 to 1092 MPa The experimental results show that the basketweave alloys have better compressive creep resistances than those duplex ones. The constitutive equations in steady-state compressive creeps of duplex or basketweave structure are calculated to be =2.77×10-15(σ-710)2.1 and =2.36×10-14(σ-740)1.7 by fitting the linear regression creep curves after uniaxial compression tests. The noticeable compressive creep strains occur when the applied compression stresses are higher than the threshold stresses, i.e. 710 MPa for duplex Ti-6Al-4V ELI alloys and 740 MPa for basketweave alloys. Microstructural analysis indicates that the creep deformation of Ti-6Al-4V ELI alloys at ambient temperature is mainly controlled by dislocation slip. The creep behavior of Ti-6Al-4V ELI alloy with duplex microstructure is controlled by dislocation slip, like slip dislocations with a-type Burgers vector sliding on the basal or prismatic planes and a few c+a type dislocation sliding on the pyramidal planes. While creep mechanism for basketweave ones is dislocation glide controlled by c+a type Burgers vector sliding on the pyramidal planes and a-type sliding on the basal or prismatic planes.

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Lv, Yaru, Feng Li, Yawen Liu, Pengxian Fan i Mingyang Wang. "Comparative study of coral sand and silica sand in creep under general stress states". Canadian Geotechnical Journal 54, nr 11 (listopad 2017): 1601–11. http://dx.doi.org/10.1139/cgj-2016-0295.

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Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

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6

Takahashi, Chika, Yutaka Ishimaru, Ikuho Iida i Yuzo Furuta. "The creep of wood destabilized by change in moisture content. Part 2: The creep behaviors of wood during and immediately after adsorption". Holzforschung 59, nr 1 (1.01.2005): 46–53. http://dx.doi.org/10.1515/hf.2005.008.

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Abstract The fluidity of wood remarkably increases during moisture changes. This phenomenon is termed mechano-sorptive creep. The mechanism of mechano-sorptive creep has been studied, including a previous report by our group. Here, creep tests in bending were carried out for wood during and immediately after adsorption of moisture and after a long moisture conditioning. The effects of the rate of moisture adsorption on creep were also examined. The results and conclusions are as follows: (I) Greater creep occurred immediately after the adsorption process as compared with that after a long moisture conditioning, whereas much greater creep occurred during the same adsorption process, similar to the case of drying. Therefore, during the changes in moisture, not only destabilization but also stabilization should occur simultaneously, so that the wood during the changing process is in a remarkably unstable state. (II) Smaller creep occurred immediately after a slower adsorption as compared with that immediately after a more rapid adsorption. This suggests that wood is more stabilized during a slower versus a more rapid adsorption process. However, difference in creep between the final stages of the slower and the more rapid adsorption process was scarcely found. This is considered to result from the difference in degree of stabilization caused by the different duration of both adsorptions. In other words, this result is only an outward appearance. (III) Greater creeps were recognized during larger changes in moisture content (Δu) during the adsorption processes corresponding to the drying process. Therefore, mechano-sorptive creep depends not only on Δu but also on the range of relative humidity (RH). Larger stabilization was found during the changing process of larger Δu.

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7

Jones, David. "Creep and anti-creep". Nature 400, nr 6740 (lipiec 1999): 121. http://dx.doi.org/10.1038/22017.

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LIU, JI-HONG, XIANG-QI MENG i JIN-QUAN XU. "CREEP CONSTITUTIVE RELATIONSHIPS AND CYCLIC BEHAVIORS OF Sn96.5Ag3Cu0.5 UNDER HIGH TEMPERATURES". International Journal of Modern Physics B 22, nr 31n32 (30.12.2008): 5438–44. http://dx.doi.org/10.1142/s0217979208050620.

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As a lead-free solder, Sn 96.5 Ag 3 Cu 0.5 has a wide application in electronic packaging. Since the solder materials usually work under cyclic temperature surroundings, creep constitutive relationships and cyclic behaviors are necessary to carry out the thermal stress analysis of a package with such a solder for its strength and life evaluations. This paper has investigated the creep constitutive relationships by constant (non-cyclic) loadings firstly, based on the creep test results at various stress and temperature levels. The complete form of the constitutive relationship containing both the linear viscous and hyperbola-sine creeps is proposed. Secondly, through the tests under cyclic stress loadings, the cyclic stress-strain relationships have been illustrated.

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9

Innes, Martin. "Control Creep". Sociological Research Online 6, nr 3 (listopad 2001): 13–18. http://dx.doi.org/10.5153/sro.634.

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Reacting to the attacks on September 11th and subsequently, governments in both the USA and UK have identified a need to enhance the social control apparatus in order to protect citizens from forms of ‘asymmetric warfare’ conducted by terrorist groups. These attempts to reform the provision of security and control cannot be understood in isolation. They are connected to a deeply entrenched process of ‘control creep’, whereby the social control apparatus progressively expands and penetrates (or ‘creeps’) into different social arenas, in response to a set of inchoate fears about a sense of security in late-modernity.

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10

Constantinescu, Dan Mihai, Radu Catalin Picu, Marin Sandu, Dragos Alexandru Apostol, Adriana Sandu i Florin Baciu. "Behaviour of Epoxy Silica Nanocomposites Under Static and Creep Loading". ACTA Universitatis Cibiniensis 69, nr 1 (20.12.2017): 1–8. http://dx.doi.org/10.1515/aucts-2017-0001.

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Abstract Specific manufacturing technologies were applied for the fabrication of epoxy-based nanocomposites with silica nanoparticles. For dispersing the fillers in the epoxy resin special equipment such as a shear mixer and a high energy sonicator with temperature control were used. Both functionalized and unfunctionalized silica nanoparticles were added in three epoxy resins. The considered filling fraction was in most cases 0.1, 0.3 and 0.5 wt%.. The obtained nanocomposites were subjected to monotonic uniaxial and creep loading at room temperature. The static mechanical properties were not significantly improved regardless the filler percentage and type of epoxy resin. Under creep loading, by increasing the stress level, the nanocomposite with 0.1 wt% silica creeps less than all other materials. Also the creep rate is reduced by adding silica nanofillers.

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11

Gorman, Susanna M. "Ethics Creep or Governance Creep?" Monash Bioethics Review 29, nr 4 (wrzesień 2011): 23–38. http://dx.doi.org/10.1007/bf03351328.

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12

Hirano, Akihiko, Masao Sakane i Naomi Hamada. "OS18-1-1 Determination of Creep Exponent and Coefficient by Indentation Creep". Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2007.6 (2007): _OS18–1–1——_OS18–1–1—. http://dx.doi.org/10.1299/jsmeatem.2007.6._os18-1-1-.

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13

Saxena, Ashok. "Creep and creep–fatigue crack growth". International Journal of Fracture 191, nr 1-2 (luty 2015): 31–51. http://dx.doi.org/10.1007/s10704-015-9994-4.

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14

Gupta, C., Hiroyuki Toda, C. Schlacher, Peter Mayr, Christof Sommitsch, Kentaro Uesugi, Yoshio Suzuki, Akihisa Takeuchi i Masakazu Kobayashi. "Study of Creep Damage in a 10.86% Cr Heat Resistant Steel using Synchrotron X-Ray Microtomography". Advanced Materials Research 794 (wrzesień 2013): 476–83. http://dx.doi.org/10.4028/www.scientific.net/amr.794.476.

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Synchrotron X-ray microtomography(SR-μCT) scans have been carried out on sample coupons extracted from the fracture specimens of a 10.86% Cr heat resistant steel exposed to crep deformation at 873K over stresses of 120, 150, and 180 MPa. The 3D cavitation characteristics in terms of void volume fraction, numbwer density and size distribution as a function of the applied stress has been determined by quantitative analysis of the reconstructed tomograohy slice datasets. The relationship between heterogenous spatial distribution of creep voids and variation in rupture life has been exploited in terms of microstructural sites during the onset of creep embrittlement.

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15

Liu, Xiaolan, Yong Zheng, Jifei Cao, Yaohui Wang, Yongqian Ma i Yantao Bi. "Study on the Influence of Gas Hydrate Reservoir Creep on Borehole Wall Deformation". Journal of Physics: Conference Series 2442, nr 1 (1.02.2023): 012035. http://dx.doi.org/10.1088/1742-6596/2442/1/012035.

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Abstract Hydrate decomposition caused by long-time drilling operations will reduce the strength of the reservoir and increase the risk of borehole wall damage. At the same time, the creep characteristics of the hydrate reservoir may also lead to engineering problems such as borehole shrinkage and sticking in the later stage of drilling, which seriously affects the drilling safety. The creep parameters are introduced to explore the influence mechanism of hydrate decomposition, and hydrate-bearing sediment creeps characteristics on wellbore mechanical behavior. The influence law of sediment shale content and hydrate saturation on wellbore stability during hydrate reservoir drilling is analyzed. The result shows the hydrate-bearing sediments creep characteristics will lead to the homogenization of stress distribution in different directions of the hydrate reservoir around the well, make theplastic yield zone shape around the well to circular, and may lead to the overall collapse of the well wall. Drilling for a long time will lead to a greater hydrate decomposition range and plastic yield zone around the well. Lower initial hydrate saturation, smaller sediment strength, and larger initial plastic strain and yield range of the formation. Increase of shale content will enhance the creep characteristics of sediments and aggravate yield degree of formation.

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16

Ellebrecht, Nils, i Dominik Weber. "Verbotener function creep". Kriminologisches Journal, nr 2 (2.06.2021): 86–104. http://dx.doi.org/10.3262/kj2102086.

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Forensische Bestimmungen der biogeographischen Herkunft eines/einer unbekannten Verdächtigen anhand von DNA-Spuren sind in Deutschland nicht erlaubt, kommen aber bereits zur Anwendung. Dieser function creep ist nur zum Teil durch rechtliche Sonderregelungen und Graubereiche gedeckt. Dieser Artikel zeigt, dass die Herkunft eines/einer Verdächtigen bereits beim DNA-Profilabgleich eine Rolle spielt. Von hier aus reift die Herkunftsanalyse zu einem eigenständigen Verfahren heran, dessen verbotener Einsatz durch drei Entwicklungen gefördert wird. (1) In den Laboren werden Herkunftsinformationen im Zuge von DNA-Analysen teilweise ungewollt sichtbar. (2) Die Popularisierung und Automatisierung von Herkunftsanalysen haben diese massiv erleichtert. (3) Kontrolldefizite führen dazu, dass Analysen formal erlaubt und durchgeführt werden, obwohl es keine rechtliche Grundlage gibt. Function creeps hängen folglich nicht nur von technischen, sondern auch von institutionellen Machbarkeiten ab.

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17

Langdon, Terence G. "Creep at low stresses: An evaluation of diffusion creep and Harper-Dorn creep as viable creep mechanisms". Metallurgical and Materials Transactions A 33, nr 2 (luty 2002): 249–59. http://dx.doi.org/10.1007/s11661-002-0087-4.

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Shao, Yawu, Yonglu Suo, Jiang Xiao, Yuan Bai i Tao Yang. "Creep Characteristic Test and Creep Model of Frozen Soil". Sustainability 15, nr 5 (22.02.2023): 3984. http://dx.doi.org/10.3390/su15053984.

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In order to research the creep deformation characteristics of frozen soil and the effect of various influencing factors on creep, indoor uniaxial creep tests were carried out on frozen soil specimens at temperatures of −5, −4, −3 and −2 °C under loads of 0.25, 0.5, and 0.75 σt, respectively. The creep deformation characteristics of frozen soil under different temperatures and load conditions are analyzed under unconfined conditions. The results show that under the uniaxial creep test conditions, when the load is low, there is no accelerated creep stage in the creep curve, which belongs to the decaying type creep; when the load is 0.75 σt, the creep curve enters the stage of accelerated creep, and the creep turns non-attenuated; temperature is the most important external factor affecting permafrost soil creep, and the proportion of ice is the key internal factor for affecting permafrost soil creep, the temperature is negatively correlated with the proportion of ice and the sensitivity of creep rate to temperature and load increases with the decrease of the proportion of ice; the damage variable D is introduced to modify the creep constitutive equation of the frozen soil, the creep process of frozen soil is well described by the modified creep constitutive equation for frozen soil.

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19

Maruyama, Kouichi. "Creep Deformation and Creep Strength of TiAl." Materia Japan 35, nr 10 (1996): 1070–76. http://dx.doi.org/10.2320/materia.35.1070.

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20

Wilshire, Brian, i H. Burt. "Creep and Creep Fracture of 7010-T7351". Materials Science Forum 396-402 (lipiec 2002): 1309–14. http://dx.doi.org/10.4028/www.scientific.net/msf.396-402.1309.

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Haifanga, LI, i ZHANG Yinqi. "Creep Rate and Creep Model of Rockfill". Procedia Engineering 28 (2012): 796–802. http://dx.doi.org/10.1016/j.proeng.2012.01.812.

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Robinson, D. N., W. K. Binienda i M. Miti‐Kavuma. "Creep and Creep Rupture of Metallic Composites". Journal of Engineering Mechanics 118, nr 8 (sierpień 1992): 1646–60. http://dx.doi.org/10.1061/(asce)0733-9399(1992)118:8(1646).

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Wilshire, B., i A. J. Battenbough. "Creep and creep fracture of polycrystalline copper". Materials Science and Engineering: A 443, nr 1-2 (styczeń 2007): 156–66. http://dx.doi.org/10.1016/j.msea.2006.08.094.

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Wright, J. K., T. M. Lillo, R. N. Wright, Woo-Gon Kim, In-Jin Sah, Eung-Seon Kim, Ji-Yeon Park i Min-Hwan Kim. "Creep and creep-rupture of Alloy 617". Nuclear Engineering and Design 329 (kwiecień 2018): 142–46. http://dx.doi.org/10.1016/j.nucengdes.2017.07.014.

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Liu, Caimei, Xizhi Wu, Xiubo Liu i Xianjun Li. "Creep Performance and Life Prediction of Bamboo Scrimber under Long-Term Tension in Parallel-to-Grain". Forests 14, nr 10 (28.09.2023): 1971. http://dx.doi.org/10.3390/f14101971.

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Creep performance is a crucial factor that must be considered in structural design. This paper aims to investigate the creep failure mode, creep strain, creep compliance, and other creep properties of bamboo scrimber under long-term tension in parallel-to-grain. To establish a general creep life prediction method for the full stress level of the bamboo scrimber, a multi-branch Kelvin–Voigt model, a generalized Maxwell model, and a creep finite element simulation were employed. The results showed that the creep strain curve of bamboo scrimber included the unsteady creep stage and the stable creep stage, but not the accelerated creep stage. When the stress ratio was less than 0.3, the residual strength decreased gradually. Below 70% of the ultimate load capacity, the creep characteristics of the bamboo scrimber were linear viscoelastic, and the creep compliance was generally independent of the load level. The creep finite element model of bamboo scrimber could accurately calculate the creep deformation of specimens. Based on this creep finite element model and creep failure rules, a life prediction model for the full stress level of bamboo scrimber was established, which could accurately predict the creep life. This paper provides theoretical guidance for the creep design of bamboo scrimber in engineering structures.

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Wang, Ruihong, Yuzhou Jiang, Chao Yang, Fei Huang i Yuxuan Wang. "A Nonlinear Creep Damage Model of Layered Rock under Unloading Condition". Mathematical Problems in Engineering 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/8294390.

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Triaxial unloading creep tests of layered rock specimen of Jinping II hydropower station were carried out using the rock creep testing machine; thus the creep deformation curves under different confining pressures were acquired. The test results showed that, in addition to the obvious unloading creep characteristics of rock specimen, the nonlinear accelerating creep deformation emerged under the last stage confining stress condition, and the whole creep curves presented the typical rock creep three stages. On the other hand, the Burgers creep model constitutive equations under the three-dimensional stress state were also deduced. Based on the creep test data, through identifying the creep parameters using the optimized algorithm, the corresponding parameters of triaxial creep constitutive model were obtained. By comparative analysis of creep parameters, it can be concluded that creep parameters nonlinearly degraded with the decrease of confining pressure gradually. Moreover, when the load is below the long-term strength of rock, the creep parameters are only related to the unloading ratio, while in the case that the load is larger than the long-term strength of rock, the unloading creep parameters are related to both unloading ratio and creep time. According to the creep parameters under the first-stage stress level, and through introducing unloading ratio damage factor to describe the degrading rule of creep parameters on other stress levels, the method of uniformity determining the creep parameters was proposed. It was assumed that the damage degree in rock interior was relative to both unloading ratio and creep time; a nonlinear creep damage model of rock under unloading was proposed, which could better reflect the nonlinear characteristics of rock creep. The results showed that rock nonlinear creep damage model achieved perfectly consistent results with the creep test.

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Li, Yong, Zhusheng Shi, Yo Lun Yang i Jian Guo Lin. "Investigation of Tensile and Compressive Creep Behaviour of AA2050-T34 during Creep Age Forming Process". Key Engineering Materials 716 (październik 2016): 323–30. http://dx.doi.org/10.4028/www.scientific.net/kem.716.323.

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The tensile and compressive creep behaviour of aluminium alloy 2050 with T34 initial temper (AA2050-T34) during creep-ageing process has been experimentally investigated and analysed in detail. Both tensile and compressive creep-ageing tests under various stress levels (ranging from 100 MPa to 187.5 MPa) have been carried out at a temperature of 155 °C for 18 hours. The results show that creep strains under tensile stresses are much larger than those under the same levels of compressive stresses and a new “double primary creep feature” with five-stage creep behaviour has been observed in the alloy during the creep-ageing tests. The conventional power-law creep equation was applied to analyse the new creep behaviour of the alloy at the steady-state creep stage. Furthermore, the power-law relationship between the applied stress and the corresponding creep strain rate was found to be effective in all creep-ageing stages of the alloy and was used for further analysis. These analyses indicate that the dislocation and diffusion mechanisms may both contribute to this new creep behaviour and may play different roles in different creep-ageing stages. Moreover, the evolution of the creep resistance or threshold creep stress of the alloy during the creep-ageing process was quantitatively investigated by the proposed relationship. These results help to not only understand the new creep behaviour of AA2050-T34 during the creep-ageing process, but also facilitate further constitutive modelling of this new creep behaviour for its creep age forming applications.

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Shenoi, R. A., H. G. Allen i S. D. Clark. "Cyclic creep and creep-fatigue interaction in sandwich beams". Journal of Strain Analysis for Engineering Design 32, nr 1 (1.01.1997): 1–18. http://dx.doi.org/10.1243/0309324971513175.

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The main emphasis of this paper is to identify long-term effects such as creep and creep-fatigue interaction for a typical sandwich structure incorporating FRP (fibre-reinforced plastic) faces and a PVC (polyvinyl chloride) foam core. For the creep modelling a Bürger model and a power law model are investigated and compared with experimental results. Fatigue results pertaining to a cyclic trapezoidal waveform are presented in the context of the creep-fatigue interaction. A cyclic creep model is developed in order to investigate the effect of cyclic creep deformation on a response containing elements of fatigue and creep. A simple linear damage rule separating the creep and fatigue components for the chosen cyclic waveform is used in order to quantify the relative influence of both components on the lifetime of the structure. Finally conclusions are drawn regarding the aptness of the chosen creep and creep-fatigue interaction models.

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Ishikawa, H. "Relation Between Cyclic Creep and Pure Creep on Copper". Journal of Engineering Materials and Technology 109, nr 3 (1.07.1987): 221–25. http://dx.doi.org/10.1115/1.3225967.

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The behavior of a pure copper subject to pure creep and cyclic creep under imposed load is examined at room temperature, and at 200°C, 300°C, and 400°C to show the relation between these two kinds of phenomena. Plots of observed strain, not against number of cycles, but against time are available for the direct comparison between cyclic creep and pure creep. This unified treatment shows that the instantaneous strain affects the succeeding mechanism of both pure creep and cyclic creep. As the result, these two kinds of phenomena are essentially identified, and pure creep could be regarded as the extreme aspect of cyclic creep.

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Zhang, Jie, Qiuhua Rao i Wei Yi. "A New Creep–Fatigue Interaction Model for Predicting Deformation of Coarse-Grained Soil". Materials 15, nr 11 (30.05.2022): 3904. http://dx.doi.org/10.3390/ma15113904.

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Studying the creep–fatigue interaction of the coarse-grained soil (CGS) is very important for safety assessment and disaster prevention in subgrade engineering. Current research work is mainly focused on single creep or fatigue deformation. In this paper, a new creep–fatigue interaction model is established to predict the creep–fatigue interaction deformation of different gradation CGS based on the rheological mechanics and the interactive relationship between creep and fatigue complex compliance method. Triaxial creep–fatigue interaction tests of different gradations CGS under different average stresses and frequencies were conducted to verify the new creep–fatigue interaction model. Research results show that for the creep–fatigue and fatigue–creep interaction, the fatigue deformation is always larger than the creep deformation under the same stress level. For the creep–fatigue multi-interaction, the second creep and fatigue deformation are always smaller than the first creep and fatigue deformation. The results of the triaxial creep–fatigue interaction tests verify the validity of this new model.

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Park, Yeong-Seong, Yong-Hak Lee i Youngwhan Lee. "Description of Concrete Creep under Time-Varying Stress Using Parallel Creep Curve". Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/9370514.

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An incremental format of creep model was presented to take account of the development of concrete creep due to loading at different ages. The formulation was attained by introducing a horizontal parallel assumption of creep curves and combining it with the vertical parallel creep curve of the rate of creep method to remedy the disadvantage of the rate of creep method that significantly underestimates the amount of creep strain, regardless of its simple format. Two creep curves were combined by introducing an ageing parameter whose value was obtained from two sets of time-dependent laboratory experiments on cylindrical specimens. The presented creep description takes the advantage that a single creep curve due to the initial loading describes the entire development of creep under the persistent change of creep-causing stress. Further, the creep formulation takes advantage of being consistent with the incremental format of age-dependent constitutive formulation. The performance of the presented creep equation was investigated with time-dependent laboratory experiments on cylindrical specimens and compared with the performances of four existing creep models.

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Sato, Hiroyuki, Kosuke Omote i Akira Sato. "Extrapolation of Creep Curve and Creep Rate by Strain Acceleration Parameter in Al-Mg Solid Solution Alloys". Materials Science Forum 794-796 (czerwiec 2014): 307–12. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.307.

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It has been widely accepted that the creep characteristics at high temperatures are mainly evaluated by a minimum creep rate. Although, a shape of creep curve may vary depending on deformation conditions, the apparent steady state or minimum creep rates be the same. Thus,for detailed analysis and prediction of creep behavior, other values which reflect the shape of each creep curve should be considered. For the purpose, authors have proposed Sato’s strain- acceleration-parameter (Strain Acceleration and Transition Objective index, SATO-index) which reflects strain rate change during creep deformation. Based on the concept of SATO-index, the whole creep curve can be represented by a set of small number of numerical parameters, and can be extrapolated from a part of creep curve. In this paper, application of the concept of SATO-index to the creep curves of aluminum-magnesium solid solutions that the creep behavior of the alloys are well investigated and analyzed. The creep curve can be extrapolated by the concept from transient part of creep curve, and the extrapolated creep rates at the minimum creep rate agree well with experiment. Efficiency of the concept of SATO-index to creep experiments is pronounced.

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Fish, Anatoly M. "Shape of creep curves in frozen soils and polycrystalline ice". Canadian Geotechnical Journal 24, nr 4 (1.11.1987): 623–29. http://dx.doi.org/10.1139/t87-076.

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A new method was developed for determining creep parameters, particularly the time to failure, from a single linear plot in which an individual creep curve forms a straight line for primary and tertiary creep. Secondary creep is considered to be a principal point on this line that predetermines the onset of failure. The times to failure can be predicted even when creep tests are not complete by extrapolating information obtained for primary creep. Based upon T. H. Jacka's test data, prediction of creep strain was evaluated using the constitutive equation of A. M. Fish for entire creep and compared with the modified Sinha equation of M. F. Ashby and P. Duval for attenuating creep as well as with models for primary and secondary creep. It is shown that the shape of the creep curves, and thus the creep parameters, varies with stress, temperature, and other factors. Hence, a family of creep curves cannot be described by a constitutive equation with a single set of creep parameters that do not take into account these variations without loss in the accuracy of the creep strain calculations. Key words: frozen soil, polycrystalline, ice, creep, failure, time to failure, attenuation, constitutive modelling.

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Kim, Seung-Gyu, Yeong-Seong Park i Yong-Hak Lee. "Comparison of Concrete Creep in Compression, Tension, and Bending under Drying Condition". Materials 12, nr 20 (15.10.2019): 3357. http://dx.doi.org/10.3390/ma12203357.

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Three types of creep experiments of compression, tension, and bending were implemented to identify quantitative relations among the three types of creep under drying atmospheric conditions. In case of the bending creep experiment, two types of unreinforced concrete beams with similar dimensions were cast for use in the beam creep and shrinkage tests. The variations in the shrinkage strain within the beam depth were measured to evaluate the effect of the shrinkage variations on the bending creep strain. The beam creep strain measured within the beam depth was composed of uniform and skewed parts. The skewed parts of the creep strain were found to be dominant whereas the uniform parts were small enough to be neglected in the bending creep evaluation. This indicated that the compressive bending creep at the top surface was close to the tensile bending creep at the bottom surface. The ratios of tensile and bending creep strains to compressive creep strain were approximately 2.9 and 2.3, respectively, and the ratio of bending creep strain to tensile creep strain was approximately 0.8. Particular attention is laid on the close agreement between tensile and compressive bending creep strains even if the creep in tension is 2.9 times larger than the creep strain in compression.

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35

Fu, Jianghua, Yang Liu, Jintao Su, Bao Chen i Zheming Chen. "Rubber Creep Model and Its Influence on Mounting Stiffness". Applied Sciences 12, nr 24 (12.12.2022): 12764. http://dx.doi.org/10.3390/app122412764.

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The mount of the engine will creep under the action of long-term load. Creep will change its original structure, resulting in changes in static and dynamic characteristics and fatigue life. In order to solve the problem of mounting rubber creep, the creep characteristics were studied in this paper. In order to study the influence of creep characteristics on engine mounting stiffness, a theoretical model of mount creep was established based on the creep mechanism of rubber. The effects of different loads on the creep characteristics of engine mount were studied. The static viscoelastic parameters and creep analysis of rubber mounting were analyzed numerically. The creep variation law of suspension under different loads is obtained. By analyzing the static and dynamic characteristics of no creep, 2.98 mm creep and 3.83 mm creep of engine mount, the creep characteristics and the variation law of mount stiffness of rubber mount were revealed. The results show that the static stiffness of suspension increases with the increase of creep. When the frequency is constant and the creep increases, the dynamic stiffness of the suspension increases obviously. In this paper, the creep characteristics of rubber mount are analyzed, and the results of the analysis provide a design method for rubber mount design.

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Sato, Hiroyuki. "Extrapolation of Imaginal Minimum Creep Rate in Compression by a Concept of SATO-Index". Key Engineering Materials 741 (czerwiec 2017): 99–104. http://dx.doi.org/10.4028/www.scientific.net/kem.741.99.

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Creep characteristics of alloys and compounds have been evaluated mainly by the minimum creep rate or the steady-state creep rate, and by its stress and temperature dependences. In some cases, however, direct comparison of the minimum creep rate or the steady-state creep rate are not practically easy due to difficulties of experiment, i.e., a long duration of primary stage of creep deformation. The minimum creep rates are not always precise representative value, which is directly evaluated from experiments. It should be valuable, if one could estimate the minimum creep rate from creep curve in primary stage. I have proposed a method of quantitative evaluation of creep curve based on the evaluation of strain rate change and its strain dependence during creep [1-3]. The value that reflects a shape of creep curve is named “Strain Acceleration and Transition Objective-Index (SATO-Index)” [4]. SATO-Index and related differential equation show a strain dependence of strain rate and lead entre creep curve by numerical integration. This concept provides quantitative information of shape of each creep curve, and information of the entire creep curve. In this paper, examples of evaluation and extrapolation of creep rate from primary stage in compression are presented. It is concluded that the extrapolation with the concept of SATO-Index reasonably provides imaginal minimum creep rate. Usability of extrapolation of creep curve by the concept is presented.

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37

Zhao, Baoyun, Wei Huang, Zhile Shu, Mengmeng Han i Yanbo Feng. "Experimental and Theoretical Studies on the Creep Behavior of Bayer Red Mud". Advances in Civil Engineering 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/6327971.

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Long-term stability and safety of the Bayer red mud (BRM) disposal field is very important for the local residents’ life, which necessitates the knowledge of its creep behavior. In order to investigate the creep behavior of BRM, a series of triaxial drained creep tests were conducted by using an improved triaxial creep apparatus. The results indicate that the creep behavior of BRM is significant with confining and deviatoric stresses being critical factors. The creep strain is in a nonlinear relationship with stress and time, and a larger deviator stress will lead to a larger creep strain. The main failure mechanism of BRM is plastic shear, accompanied by a significant compression and ductile dilatancy. Based on the test results, two well-established creep models, the Burgers creep model and Singh–Mitchell creep model, were used to comparatively analyze the creep behavior of the Bayer red mud under a certain stress level. Then, an improved Burgers creep damage constitutive model with the addition of a damage variable was proposed, whose parameters were also analyzed in detail. The comparison of the calculated values of the creep model and the experimental values shows that the proposed creep damage model can better describe the instant elastic deformation, attenuation creep, steady-state creep, and accelerated creep stages of the Bayer red mud.

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Saucedo-Muñoz, Maribel L., Shin-Ichi Komazaki, Toru Takahashi, Toshiyuki Hashida i Tetsuo Shoji. "Creep property measurement of service-exposed SUS 316 austenitic stainless steel by the small-punch creep-testing technique". Journal of Materials Research 17, nr 8 (sierpień 2002): 1945–53. http://dx.doi.org/10.1557/jmr.2002.0288.

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The creep properties for SUS 316 HTB austenitic stainless steel were evaluated by using the small-punch creep test at 650 °C for loads of 234, 286, 338, 408, and 478 N and at 700 °C for loads of 199 and 234 N. The creep curves, determined by means of the small-punch creep test, were similar to those obtained from a conventional uniaxial creep test. That is, they exhibited clearly the three creep stages. The width of secondary creep stage and rupture time tr decreased with the increase in testing load level. The creep rupture strength for the service-exposed material was lower than that of the as-received material at high testing loads. However, the creep resistance behavior was opposite at relatively low load levels. This difference in creep resistance was explained on the basis of the difference in the creep deformation and microstructural evolution during tests. It was also found that the ratio between the load of small-punch creep test and the stress of uniaxial creep test was about 1 for having the same value of creep rupture life.

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Zheng, Jing-Hua, Yufeng Jin, Lang Xu, Congze Fan, Wenzhe Song i Yiwei Chen. "Comparative Study of Creep and Stress Relaxation Behaviour during Ageing of 7050 Aluminum Alloy". Metals 13, nr 4 (16.04.2023): 778. http://dx.doi.org/10.3390/met13040778.

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This work focuses on quantitatively investigating the relationship between creep and stress relaxation of 7050 aluminum alloy at ageing temperatures. The creep strain rates, creep exponent, n, and activation energy were extracted from both the creep and stress relaxation curves to explore the creep mechanisms. Results showed that higher applied stress promotes the creep and stress relaxation extents. The calculated creep strain rates from creep and stress relaxation curves located in similar ranges and share similar n values (n = 3.7 for creep and n = 3.5 for stress relaxation), indicating that both tests are dominated by the dislocation slip mechanism. Additionally, the n value for creep tests is a constant throughout the tests, indicating that the dominant creep mechanism is unchanged. However, the activation energy changes from 123 kJ/mol to 139 kJ/mol, possibly due to evolved dislocations. Such a new finding could provide a supporting mechanism for building constitutive equations depending on the evolved A value. Furthermore, compared to the single-stage creep ageing, no primary creep was observed in T74 multi-stage creep ageing while similar amount of total creep strains was achieved. This suggests an alternative loading sequence for creep age forming of 7050 aluminum alloy, i.e., loading at the second stage to avoid prolonged exposure to high temperatures, extend the tool life, and achieve similar amounts of inelastic deformations. Based on all the above studies, creep and stress relaxation have a certain relationship. This paper provides a theoretical basis for future research on creep ageing forming of 7050 aluminum alloy.

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Sato, Hiroyuki, Kosuke Omote, Akira Sato i Kouki Ueno. "Extrapolation of Sigmoidal Creep Curve by Strain Acceleration Parameter". Key Engineering Materials 592-593 (listopad 2013): 606–9. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.606.

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It has been widely accepted that the creep characteristics at high temperatures are mainly evaluated by a minimum creep rate and a time to fracture. Although, a shape of creep curve may vary depending on deformation conditions, the apparent minimum creep rates may become the same value. Thus, for detailed analysis and prediction of creep behavior, other values should be considered which reflects the shape of each creep curve. For the purpose, authors have proposed Satos Strain-Acceleration-Parameter (SAP) which reflects strain rate change during creep. Based on the concept of SAP, the whole creep curve can be represented by a set of small numbers of numerical parameters, and can be extrapolated from a part of creep curve [. It is also well accepted that the creep rates depend on microstructures, and microstructural changes cause strain rate change. The SAP would reflect stability and magnitude of microstructural change during deformation at high temperatures. In this paper, application of the concept of SAP to creep curves that show sigmoidal type primary creep is presented. The creep curve can be divided into two regime based on the SAP values. The sigmoidal creep curve is reasonably reproduced by the concept of Strain-Acceleration-Parameter, and reasonably agrees with experiment. Whole creep curve can be reasonably represented by a few numerical values which reflect shape of creep curve in each regime. The concept of SAP is applicable for quantitative evaluation of both normal and sigmoidal type of creep curves.

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Meraj, Md, i Snehanshu Pal. "An Anomaly in Creep Property Dependence on Grain Size for Ultrafine Grain Nanocrystalline Nickel at Higher Creep Temperature". Materials Science Forum 978 (luty 2020): 477–86. http://dx.doi.org/10.4028/www.scientific.net/msf.978.477.

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In this present study, molecular dynamics simulation of creep for ultrafine grain NC Ni specimens with different grain sizes have been carried out under a constant 1 GPa applied load for various creep temperatures to study the dependence of grain growth on creep temperature and grain size during creep process and its influence on creep properties. It is observed that the extent of grain growth in ultrafine grain NC Ni during creep deformation process is more if creep in creep temperature is higher. A noteworthy anomaly, that is NC Ni with smaller grain exhibits better creep property compared to NC Ni with larger grain, is observed in case of higher creep temperatures (i.e. around or greater than 1400K).

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Pan, Jingping, Shuheng Tu, Xinwei Zhu i Lianjiang Tan. "Creep behavior and cavitation evolution of 15CrMoG steel at high temperatures". Advances in Mechanical Engineering 11, nr 8 (sierpień 2019): 168781401986566. http://dx.doi.org/10.1177/1687814019865669.

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15CrMoG steel is a type of heat-resistant steel frequently used in boiler and piping systems. Creep properties of the 15CrMoG steel at service temperatures are not much documented due to the difficulties in obtaining long-term creep data. Herein, the creep behavior and the cavity evolution of 15CrMoG steel were investigated based on 20,000 h of creep tests at varied temperatures. Creep curves were analyzed to elucidate the creep behavior and creep rupture mechanism of the 15CrMoG steel. A continuum damage model was adopted to fit the rupture stress versus creep time data, and the results showed the reliability of this model in describing the creep behavior and predicting the creep life. The creep rupture stress at 20,000 h decreased significantly with the increase in the temperature in the tested temperature range. The cavitation in the 15CrMoG steel samples occurring during the creep tests was also examined by microscopic analysis, the results of which confirmed that the cavitation evolution is responsible for the reduced mechanical performance and finally creep rupture of the steel. This work provides valuable high-temperature creep data of the 15CrMoG heat-resistant steel and insights into evaluation and prediction of long-term creep behavior at high temperatures.

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Ren, Fa Cai, Xiao Ying Tang i Jun Si. "Investigation on Creep Properties of Welded Joint of Modified 9Cr-1Mo Martensitic Heat-Resistant Steel". Key Engineering Materials 795 (marzec 2019): 312–17. http://dx.doi.org/10.4028/www.scientific.net/kem.795.312.

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The creep rupture behavior of weld joint of modified 9Cr-1Mo martensitic heat-resistant steel is investigated by conducting creep tests. The creep strain-time curves of 838K under different stress levels are obtained. The effects of different stress conditions on the creep rupture lifetime are analyzed. Based on the creep test data, the relationship between minimum creep rate and stress, creep rupture time is analyzed. The test results show that the creep rupture occurred in the fine-grained heat-affected zone. The microstructure evolution during creep process is studied by metallographic analysis and fracture analysis.

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Qiu, Y. Y., Z. Dong, X. L. Song i Z. D. Xiang. "A new tensile creep model for predicting long-term creep strengths with short-term test data for creep resistant alloys". Journal of Physics: Conference Series 2680, nr 1 (1.01.2024): 012018. http://dx.doi.org/10.1088/1742-6596/2680/1/012018.

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Abstract The difficulties in using the conventional Norton creep model to rationalise short-term creep data and to subsequently predict long-term creep rupture strengths for creep resistant alloys are presented and analysed. The results of this study show that these difficulties can be resolved if a new tensile creep model that integrates the tensile strength at creep temperature is applied to rationalise the short-term creep data. This is illustrated with the creep and tensile strength data measured for a grade of Ni-based superalloy. Based on this new tensile creep model, the activation energy of creep determined is independent of stress and the stress exponent is not influenced by temperature. Consequently, the model constants obtained from the short-term creep data can be applied together with the Monkman-Grant relationship to make the long-term creep rupture strength predictions at different temperatures. The factors affecting the reliability of the predictions made by this method are also analysed.

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Kim, Woo Gon, Sang Nan Yin, Woo Seog Ryu i Jong Hwa Chang. "Creep Properties of Hastelloy-X Alloy for the High Temperature Gas-Cooled Reactor". Key Engineering Materials 326-328 (grudzień 2006): 1105–8. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1105.

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The creep properties for the Hastelloy-X alloy which is one of candidate alloys for a high temperature gas-cooled reactor are presented. The creep data was obtained with different stresses at 950oC, and a number of the creep data was collected through literature surveys. All of the creep data were combined together to obtain the creep constants and to predict a long-term creep life. In the Norton’s creep law and the Monkman-Grant relationship, the creep constants, A, n, m, and m’ were obtained. Creep master curves based on the Larson-Miller parameter were presented for the standard deviations of 1σ, 2σ and 3σ. Creep life at each temperature was predicted for a longer-time rupture above 105 hours. Failure probability was also estimated by a statistical process of all the creep rupture data.

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46

Ekaputra, I. M. W., i Gunawan Dwi Haryadi. "Karakteristik Laju Regangan Melar pada Baja Tahan Karat Austenitic 316L". ROTASI 19, nr 4 (3.10.2017): 201. http://dx.doi.org/10.14710/rotasi.19.4.201-205.

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In this study, the creep strain rate characteristics of austenitic 316L stainless steel was investigated from the uniaxial creep-rupture test. The tests were conducted under various applied load levels with a constant temperature at 525oC. The creep exponent was obtained by applying a Norton’s law equation on a regression line of creep strain rate vs. stress curve. The steel clearly showed an instantaneous primary stage, following with the secondary and tertiary stages on the creep curve. It was found that the creep rupture time decreased systematically with an increase in the stress. The secondary stage of creep curve almost dominated the creep’s lifetime. Therefore, the creep strain rate was determined from the minimum strain rate on this stage. The obtained creep exponent indicated that the responsible creep mechanism was grain boundary sliding or diffusional creep mechanism

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Jiang, Yu-Qiang, Y. C. Lin, C. Phaniraj, Yu-Chi Xia i Hua-Min Zhou. "Creep and Creep-rupture Behavior of 2124-T851 Aluminum Alloy". High Temperature Materials and Processes 32, nr 6 (1.12.2013): 533–40. http://dx.doi.org/10.1515/htmp-2012-0172.

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AbstractHigh temperature creep and useful creep life behavior of Al-Cu-Mg (2124-T851 aluminum) alloy was investigated by conducting constant stress uniaxial tensile creep tests at different temperatures (473–563 K) and at stresses ranging from 80 to 200 MPa. It was found that the stress and temperature dependence of minimum creep rate could be successfully described by the power-law creep equation. The power-law stress exponent, n = 5.2 and the activation energy for secondary creep, Q = 164 kJ mol−1, which is close to that observed for self diffusion of aluminum (~140 kJ mol−1). The observed values of n and Q suggest that the secondary creep of 2124-T851 aluminum alloy is governed by the lattice diffusion controlled dislocation climb process. A Monkman-Grant type relationship between minimum creep rate and time for reaching 1.5% creep strain is proposed and could be employed for predicting the useful creep life of 2124-T851 aluminum alloy.

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Du, Xing Hao, Guang Ye Zhang i Jian Ting Guo. "Microstructure and High-Temperature Creep Behavior of NiAl-25 at.% Cr Intermetallic Compound". Materials Science Forum 475-479 (styczeń 2005): 771–74. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.771.

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The creep behavior and mechanisms of extruded NiAl-25Cr alloy at elevated temperatures have been studied in the paper. Analysis of the creep data over the temperature range 1073-1123 K reveals two distinct regions of creep behavior present in this material. At lower temperature, the creep characteristics are consistent with mobility-controlled deformation where viscous glide of dislocations controls creep. At higher temperature, the creep characteristics are consistent with a structure controlled creep process where some form of dislocation climb controls creep deformation.

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Sklenička, Vàclav, Květa Kuchařová, Jiří Dvořák, Marie Kvapilová i Petr Král. "Creep Damage Tolerance Factor λ of Selected Creep-Resistant Steels". Key Engineering Materials 754 (wrzesień 2017): 47–50. http://dx.doi.org/10.4028/www.scientific.net/kem.754.47.

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The creep damage tolerance factor λ as an important outcome of the continuum damage mechanics approach has been used to asses the creep fracture mode and the susceptibility of material to localized cracking at strain concentrations. In this work, using sets of our earlier published creep data of three advanced ferritic creep-resistant steels (T23 low alloy steel, P91 and P92 chromium steels) are analysed in terms of the creep damage tolerance factor λ. It was found that the value of the creep damage factor λ is not constant and depends on the creep loading conditions. The data analysis is followed by fractographic investigations, which is used to identify the creep fracture mode (s) experimentally.

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Wilczynski, Przemyslaw Michal, Andrzej Domonik i Pawel Lukaszewski. "Brittle Creep and Viscoelastic Creep in Lower Palaeozoic Shales from the Baltic Basin, Poland". Energies 14, nr 15 (30.07.2021): 4633. http://dx.doi.org/10.3390/en14154633.

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The paper analyses the mechanical properties of shales from the Baltic Basin, focusing on creep strain in conditions of variable stress and elevated temperature (85 °C). Rock samples were collected from drill cores from various depths between 3600–4000 m. A series of creep tests was performed using a triaxial apparatus in simulated pressure and temperature conditions in the reservoir. The creep tests were conducted at variable levels of differential stress in variable time intervals. The laboratory experiments were performed in order to study brittle and viscoelastic creep proceeding in time in shales rich in organic matter and clay minerals. Creep compliance of shale formations rich in organic matter influences the success of hydraulic fracturing procedures, as well as migration of natural gas during exploitation. Laboratory characteristics of geomechanical properties (compressive strength, strain and elastic moduli) is crucial for planning natural gas exploitation from unconventional resources. The results indicate that the level of constant differential stress and creep time significantly influence the mechanical properties of shales. The paper presents the differences between brittle and viscoelastic strain registered during creep tests at variable stress conditions and time intervals. In viscoelastic creep tests, creep strain is over two times larger in the second stage of creep in comparison to the magnitude of strain registered in the first stage. In brittle creep tests, axial strain in the first creep stage is two times larger than in viscoelastic creep tests in the second stage. Based on the experiments, elastic parameters, i.e., Young’s modulus and Poisson’s ratio, have been determined for each of the analysed samples. In brittle creep tests, Young’s modulus is smaller than in viscoelastic creep tests. In viscoelastic creep tests Young’s modulus increases in successive stages. Whereas Poisson’s ratio is larger for samples from brittle creep tests than for samples from viscoelastic creep tests and does not change with subsequent creep stages in viscoelastic creep tests.

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