Effect of Temperature on the Creep of Ice

Creep tests on homogeneous, isotropic polycrystalline ice gave an apparent activation energy for creep of 16.4 kcal/mol (68.8 kJ/mol) over the temperature range −10° to −60° C. Above −10° C the Arrhenius relation for temperature dependence is invalid, and creep rate becomes progressively more temperature dependent as the melting point is approached. Between −20° and −50° C the apparent activation energy for creep of a single crystal of ice was found to be 16.5 kcal/mol (69.1 kJ/mol). A complete creep curve for a single crystal loaded in uniaxial compression parallel to the basal plane was qualitatively similar to the classical creep curve; creep rate at all stages was very much faster than for polycrystalline ice under the same conditions. Creep tests on polycrystalline ice at 0° C gave a stress/strain-rate relation for that temperature, but its precise meaning is unclear, since recrystallization complicated the results.

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The microstructure and creep deformation of hot-pressed Si3N4 with different amounts of sintering additives

Journal of Materials Research ◽

10.1557/jmr.1996.0015 ◽

1996 ◽

Vol 11 (1) ◽

pp. 120-126 ◽

Cited By ~ 25

Author(s):

Sang-Young Yoon ◽

Takashi Akatsu ◽

Eiichi Yasuda

Keyword(s):

Activation Energy ◽

Silicon Nitride ◽

Creep Rate ◽

Grain Boundary ◽

Apparent Activation Energy ◽

Creep Test ◽

Creep Deformation ◽

Glassy Phase ◽

Microstructural Observation ◽

Rate Limiting

Compressive creep deformation of hot-pressed silicon nitride with different amounts of grain boundary glassy phase was investigated at 1300–1400 °C under 30–100 MPa. The stress exponent of the creep rate was determined to be nearly unity. The apparent activation energy of silicon nitride with a larger amount of glassy phase was measured to be about 700 kJ/mole, and that with a smaller amount of glassy phase was found to be 400 kJ/mole. In addition, the microstructural observation found that no cavity appeared and grain boundary glass was recrystallized during creep test. Thus, the rate-limiting steps in solution/precipitation creep mechanism change from the solution-reprecipitation of Si3N4 grains to the diffusion through the grain boundary with increasing the amount of glassy phase.

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Impression Creep Behaviour of Extruded Mg-Sn Alloy

International Journal of Vehicle Structures and Systems ◽

10.4273/ijvss.8.3.10 ◽

2016 ◽

Vol 8 (3) ◽

Cited By ~ 2

Author(s):

V. Thenambika ◽

S. Jayalakshmi ◽

R.A. Singh ◽

J.K. Nidhi ◽

M. Gupta

Keyword(s):

Activation Energy ◽

Stress Exponent ◽

Creep Deformation ◽

Creep Behaviour ◽

Impression Creep ◽

Temperature Dependent ◽

Creep Tests ◽

Automobile Engine ◽

Creep Curves ◽

Mg2sn Phase

Mg-Sn alloys contain thermally stable Mg2Sn phase, and are proposed as heat-resistant alloys for automobile engine applications. In this study, the creep behaviour of Mg-5Sn alloy was investigated using impression creep technique. The impression creep tests were carried out under constant punching stress in the range of 80-320 MPa at temperatures 373-573 K, for dwell times up to 5 hours. The results highlight that creep of Mg-5Sn alloy was load and temperature dependent, i.e. increasing the load and temperature resulted in larger creep deformation and hence to higher creep rates. From the creep curves, the stress exponent and the activation energy were estimated and the creep mechanism was identified.

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Creep of Heusler-Type Alloy Fe-25Al-25Co

Crystals ◽

10.3390/cryst10010052 ◽

2020 ◽

Vol 10 (1) ◽

pp. 52

Author(s):

Ferdinand Dobeš ◽

Petr Dymáček ◽

Martin Friák

Keyword(s):

Activation Energy ◽

Intermetallic Compound ◽

Creep Rate ◽

Activation Enthalpy ◽

Dislocation Climb ◽

Rate Data ◽

Type Alloy ◽

Creep Tests ◽

Multivariable Regression ◽

Apparent Activation Energies

Creep of an alloy based on the intermetallic compound Fe2AlCo was studied by compressive creep tests in the temperature range from 873 to 1073 K. The stress exponent n and the activation energy of creep Q were determined using the multivariable regression of the creep-rate data and their description by means of sinh equation (Garofalo equation). The evaluated stress exponents indicate that the dislocation climb controls creep deformation. The estimated apparent activation energies for creep are higher than the activation enthalpy for the diffusion of Fe in Fe3Al. This can be ascribed to the changes in crystal lattice and changing microstructure of the alloy.

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Does the Permanent Creep-Rate of Polycrystalline Ice Increase with Crystal Size?

Journal of Glaciology ◽

10.1017/s0022143000010364 ◽

1980 ◽

Vol 25 (91) ◽

pp. 151-158 ◽

Cited By ~ 38

Author(s):

Paul Duval ◽

Hugues Le Gac

Keyword(s):

Grain Size ◽

Creep Rate ◽

Uniaxial Compression ◽

Crystal Size ◽

Size Range ◽

Transient Creep ◽

Creep Tests ◽

Compression Creep ◽

Polycrystalline Ice

AbstractUniaxial compression creep tests were performed on artificial and natural polycrystalline ices at temperatures near –7°C. The grain-size range investigated was from 1 to 10 mm. Contrary to previous results, the permanent creep-rate was not found to increase with crystal size. Only the transient creep appears to be sensitive to variations in crystal size.

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Reactions of thiyl radicals. II. The photolysis of methyl disulfide vapor

Canadian Journal of Chemistry ◽

10.1139/v67-226 ◽

1967 ◽

Vol 45 (12) ◽

pp. 1369-1374 ◽

Cited By ~ 29

Author(s):

P. M. Rao ◽

J. A. Copeck ◽

A. R. Knight

Keyword(s):

Nitric Oxide ◽

Activation Energy ◽

Apparent Activation Energy ◽

Pressure Range ◽

Excess Energy ◽

Inert Gases ◽

Effect Of Temperature ◽

Primary Process ◽

Direct Production ◽

Thiyl Radicals

The photolysis of methyl disulfide vapor in the pressure range 2–25 Torr at wavelengths between 2 300 and 2 800 and at 2 288 Å has been examined and the effect of temperature, pressure, added inert gases, ethyl disulfide, and nitric oxide determined.The primary process is a direct production of two CH3S radicals which have excess energy and which can be observed as methyl thionitrite when NO is present during the decomposition. When pure disulfide is photolyzed the major observable product is methanethiol, although this material accounts for only a small fraction of the primarily produced thiyl radicals whose principal fate is recombination in a substrate-reforming reaction producing excited disulfide molecules. The latter species are deactivated by added gases, or by the substrate itself. The mode of mercaptan formation is by abstraction of H atoms from the substrate by excited CH3S radicals with an apparent activation energy of 1.5 kcal.

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The effect of temperature on the aggregation kinetics of partially bare gold nanoparticles

RSC Advances ◽

10.1039/c6ra17561a ◽

2016 ◽

Vol 6 (85) ◽

pp. 82138-82149 ◽

Cited By ~ 14

Author(s):

Anushree Dutta ◽

Anumita Paul ◽

Arun Chattopadhyay

Keyword(s):

Activation Energy ◽

Gold Nanoparticles ◽

Effect Of Temperature ◽

Aggregation Kinetics ◽

Temperature Dependent ◽

Colloidal Aggregation ◽

First Order ◽

First Order Kinetics ◽

Kinetics Of ◽

Bare Gold

Temperature dependent aggregation reaction of partially bare gold nanoparticles showed a first order kinetics and prevalence of reaction limited colloidal aggregation with an activation energy equal to 36.2 ± 3.0 kJ mol−1.

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Creep and Creep Recovery of 2618-T61 Aluminum Under Variable Temperature

Journal of Applied Mechanics ◽

10.1115/1.3167730 ◽

1984 ◽

Vol 51 (4) ◽

pp. 816-820 ◽

Cited By ~ 4

Author(s):

U. W. Cho ◽

W. N. Findley

Keyword(s):

Activation Energy ◽

Aluminum Alloy ◽

Apparent Activation Energy ◽

Variable Temperature ◽

Constant Stress ◽

Temperature History ◽

Effect Of Temperature ◽

Creep Recovery ◽

Dependent Theory ◽

Using Data

Creep and creep recovery data are reported for pure tension of 2618-T61 aluminum alloy under variable temperature between 200° C and 230° C. Varying temperature experiments involved an abrupt temperature increase and a linearly increasing and decreasing temperature at a constant stress of 137.9 MPa (20 ksi). A temperature-compensated time by Sherby and Dorn was employed to represent the effect of temperature. A temperature-history-dependent theory using data from constant stress creep and creep recovery together with the apparent activation energy was used to predict the creep under variable temperature. The predictions agreed quite well with the observed data. The apparent activation energy of this alloy was found to be 49,000 cal/mole°K.

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Creep of Fe–Al Alloys with Additions of Niobium and Carbon

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.465.443 ◽

2011 ◽

Vol 465 ◽

pp. 443-446 ◽

Cited By ~ 1

Author(s):

Ferdinand Dobeš

Keyword(s):

Activation Energy ◽

High Temperature ◽

Creep Rate ◽

Constant Load ◽

Al Alloys ◽

Iron Aluminide ◽

High Temperature Creep ◽

Low Carbon ◽

Creep Tests ◽

Stepwise Loading

High-temperature creep of a Fe3Al-type iron aluminide alloyed by niobium and different additions of carbon was studied in the temperature range from 600 to 800 °C. The alloys contained (atomic %) (i) 27.6 Al, 1.15 Nb, 0.19 C and (ii) 27.1 Al, 1.11Nb, 0.76 C (Fe balance). Creep tests were performed in compression at constant load with stepwise loading. Stress exponent and activation energy of the creep rate were determined. Creep resistance of the low-carbon alloy is better at lower temperatures, while the opposite is true at temperature of 800 °C.

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Creep Behavior of Two Series Magnesium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.1596 ◽

2010 ◽

Vol 638-642 ◽

pp. 1596-1601 ◽

Cited By ~ 2

Author(s):

Yang Shan Sun ◽

Jing Bai ◽

Feng Xue

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Stress Exponent ◽

Magnesium Alloys ◽

Creep Behavior ◽

Creep Deformation ◽

Grain Boundary Sliding ◽

Creep Tests ◽

Sharp Drop ◽

Creep Properties

The creep behavior of two series of magnesium alloys, Mg-4Al based alloys with strontium addition and binary Mg-Nd alloys, has been studied. Results show that the high creep properties achieved by the Mg-Nd alloys are attributed to the precipitation of tiny dispersed β’ particles, which form and effectively restrict the dislocation slipping and climb during creep deformation. In terms of values of the stress exponent and apparent activation energy gained from systematic creep tests, the mechanism responsible for creep deformation of the Mg-Nd alloys is inferred as dislocation climb, which is supported by TEM observations performed on the Mg-2Nd alloy after creep test. For the Mg-4Al based alloys, however, microstructural observations reveal that the significant improvement on creep properties caused by Sr addition is accounted for the formation of an interphase network consisting of Al4Sr and a Mg-Al-Sr ternary compound distributing at grain boundaries. The breakage of the interphase network after extrusion results in a sharp drop of creep properties, indicating the creep deformation of the alloy is controlled mainly by grain boundary sliding, which is in contradiction to the mechanism for creep of the alloys inferred by the classical criterions based on the values of stress exponent and apparent activation energy.

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