Ice crystallographic and strain rate changes with strain in compression and extension

Jacka, T. H.; Maccagnan, M.

doi:10.1016/0165-232x(84)90058-2

Cited by 153 publications

(133 citation statements)

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“…Grain-size effects, on the other hand, have received comparatively little attention. A number of papers have appeared in the literature that deal with grain-size effects on compressive creep of ice (Baker, 1978;Duval and Le Gac, 1980;Jones and Chew, 1983;Jacka, 1984;Jacka and Maccagnan, 1984). On balance, the results indicate that, while grain-size has an influence on primary creep rates, the minimum creep rate and subsequent tertiary creep appear to be unaffected by the initial grain-size of the material.…”

Section: Introductionmentioning

confidence: 84%

Strain-Rate and Grain‒Size Effects in Ice

Cole

1987

J. Glaciol.

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ABSTRACT. This paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10-7 to 10-1 S-I, grain-size rarged from 1.5 to 5.8 mm, and the test temperature was -5 C.At strain-rates between 10-7 and 10-3 S-I, the stressstrain-rate relationship followed a power law with an exponent of I! = 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 x 10-6 S-1 the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strainrates observed. At strain-rates above 10-3 S-1 the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the straininduced boundary migration characteristic of the finegrained material.

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Section: Introductionmentioning

confidence: 84%

Strain-Rate and Grain‒Size Effects in Ice

Cole

1987

J. Glaciol.

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“…no c-axes near compressional axes), a true steady state of deformation (a constant applied stress yields a constant strain rate, grainsize and c-axis fabric , and thus almost certainly a steadystate average dislocation density) and n = 3 (e.g. Jacka, 1984a, b;Jacka and Maccagnan, 1984). Ice shelves under temperatures and normal stresses approaching laboratory values develop girdle-type fabrics and are observed to spread with n = 3 (e.g.…”

Section: Fabric Effects From Jacka and Maccagnan (1984)mentioning

confidence: 99%

“…(At higher stresses than occur in natural ice sheets, n > 3 is possible. ) J acka and Maccagnan ( 1984) showed how the angle of the girdle fabric varies between onset of recrystallization and approach to steady state, and how the ice hardness depends on this angle. The values recommended by Jacka and Maccagnan provide a good starting point for modeling.…”

Section: Fabric Effects From Jacka and Maccagnan (1984)mentioning

confidence: 99%

Flow-law hypotheses for ice-sheet modeling

1992

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ABSTRACT. Ice-flow modeling requires a flow law relating strain rates to stresses in situ, but a flow law cannot be measured directly in ice sheets. Microscopic processes such as dislocation glide and boundary diffusion control both the flow law for ice and the development of physical properties such as grain-size and c-axis fabric. These microscopic processes can be inferred from observations of the physical properties, and the flow law can then be estimated from the microscopic processes.A review of available literature shows that this approach can be imperfectly successful. Interior regions of large ice sheets probably have depth-varying flow-law "constants", with the stress exponent, n, for power-law creep less than 3 in upper regions and equal to 3 only in deep ice; n probably equals 3 through most of the thickness of ice shelves and ice streams.

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“…Chauve et al: Strain field evolution at the ductile More generally, creep of isotropic polycrystalline ice is characterized by a three-stage behavior, with a strong decrease in strain rate during primary creep, down to a minimum reached at about 1 % strain, also called secondary creep, immediately followed by a increase in strain rate to reach tertiary creep at about 10 % strain (see Jacka and Maccagnan, 1984;Duval et al, 1983, for instance).…”

mentioning

confidence: 99%

“…Dynamic recrystallization leads to strong modification in microstructure and texture (Duval, 1979;Jacka and Maccagnan, 1984;Montagnat et al, 2015) through various mechanisms such as nucleation of new grains or polygonization associated with subgrain boundaries and bulging, recently characterized by cryo-EBSD (electron backscatter diffraction; Chauve et al, 2017). While Piazolo et al (2015) showed that sub-grain boundary formation such as kink bands could be correlated with heterogeneities of local stress (simulated with a full-field crystal plasticity code, CraFT), Chauve et al (2015) were able to directly associate nucleation mechanisms (polygonization, bulging) with local modification of the strain field estimated in situ from digital image correlation (DIC) measurements.…”

mentioning

confidence: 99%

Strain field evolution at the ductile-to-brittle transition: a case study on ice

et al. 2017

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Abstract. This paper presents, for the first time, the evolution of the local heterogeneous strain field around intra-granular cracking in polycrystalline ice, at the onset of tertiary creep. Owing to the high homologous temperature conditions and relatively low compressive stress applied, stress concentration at the crack tips is relaxed by plastic mechanisms associated with dynamic recrystallization. Strain field evolution followed by digital image correlation (DIC) directly shows the redistribution of strain during crack opening, but also the redistribution driven by crack tip plasticity mechanisms and recrystallization. Associated local changes in microstructure induce modifications of the local stress field evidenced by crack closure during deformation. At the ductile-to-brittle transition in ice, micro-cracking and dynamic recrystallization mechanisms can co-exist and interact, the later being efficient to relax stress concentration at the crack tips.

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Ice crystallographic and strain rate changes with strain in compression and extension

Cited by 153 publications

References 11 publications

Strain-Rate and Grain‒Size Effects in Ice

Strain-Rate and Grain‒Size Effects in Ice

Flow-law hypotheses for ice-sheet modeling

Strain field evolution at the ductile-to-brittle transition: a case study on ice

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