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

Duval, Paul; Gac, H. Le

doi:10.3189/s0022143000010364

Cited by 20 publications

(18 citation statements)

References 11 publications

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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: 85%

“…This behavior results from the fact that the coarsegrained material undergoes the transition to brittle behavior at lower strain-rates than does the fine-grained material. Other work (Duval and Le Gac, 1980;Mellor and Cole, 1982) has clearly indicated that under compressive loading the minimum strain-rate in creep tests and the peak stress in strength tests on ice occur at a relatively constant axial strain level of 0.0 I. However, it is apparent from the present work and from the results of creep tests on identical material (Cole, 1986) that the strain at either the peak stress or the minimum creep rate should be considered as a function of grain-size under certain conditions .…”

Section: Additional Discussionmentioning

confidence: 99%

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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: 85%

Section: Additional Discussionmentioning

confidence: 99%

Strain-Rate and Grain‒Size Effects in Ice

Cole

1987

J. Glaciol.

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“…I did not do that here since the grain size that was used was fairly uniform and deformation of ice under the conditions modeled does not show a strong dependence on grain size [Duval and LeGac, 1980]. However, grain size may be important when mechanisms other than intracrystalline slip contribute to the deformation [Goldsby and Kohlstedt, 1996;Cuffey et al, 2000].…”

Section: Discussionmentioning

confidence: 99%

Fabric development with nearest‐neighbor interaction and dynamic recrystallization

Þorsteinsson

2002

J. Geophys. Res.

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[1] Polycrystals undergoing ductile deformation develop lattice-preferred orientation (fabric) as a result of intracrystalline slip. A consequence of fabric development is that bulk physical properties become anisotropic. Fabric development and macroscopic deformation are studied by examining three effects: nearest-neighbor interaction (NNI) among crystals, polygonization, and migration recrystallization. The effects of NNI are modeled by arranging the crystals on a three-dimensional cubic grid and assigning six neighbors to each crystal. The ''strength'' of interaction can vary from no interaction (homogeneous stress) to ''strong'' interaction (significant stress redistribution). Increasing the NNI leads to a more homogeneous strain. Fabric varies in both strength and symmetry at a given bulk strain, depending on the strength of NNI. For a prescribed fabric the strain rate increases as the NNI increases. Recrystallization is modeled from energy balance considerations, and polygonization is formulated in terms of stress differences. Both processes require knowledge of dislocation density, which is calculated in the model as a function of crystal strain and grain size, both of which vary with time. Models of fabric development in ice that include NNI lead to more realistic fabric evolution than models with homogeneous stress. However, available data on fabric evolution are inadequate to determine quantitatively the strength of NNI acting in ice.

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“…Explanations for this grain-growth reduction have been discussed for many years (e.g. Gow and Williamson, 1976;Duval and Gac, 1980;Paterson, 1994), but there is, as yet, no consistent understanding to be found in the literature. In laboratory ice deformation experiments Jacka and Li (1994) found a steady-state crystal size with the tertiary creep stage.…”

Section: Introductionmentioning

confidence: 99%

Evolution of ice crystal microstructure during creep experiments

Hamann¹,

Weikusat²,

Azuma³

et al. 2007

J. Glaciol.

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ABSTRACT. Results of laboratory uniaxial compression tests over the stress range 0.18-0.52 MPa and the strain range 0.5-8.6% at approximately -5 and -208 8C are presented. Grain-size analysis and comparisons with annealing tests confirm that grain-growth reducing processes are active during deformation. Microstructural observations reveal that subgrain-rotation recrystallization and grainshape changes due to strain-induced grain-boundary migration are the causes of the grain-growth deceleration. Further results from microstructural observations show that obstacle formation by dislocation walls and subgrain boundaries is the reason for isotropic hardening during creep. Subgrainboundary types that are likely to be relevant for studies on the activity of different dislocation types are described.

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

Cited by 20 publications

References 11 publications

Strain-Rate and Grain‒Size Effects in Ice

Strain-Rate and Grain‒Size Effects in Ice

Fabric development with nearest‐neighbor interaction and dynamic recrystallization

Evolution of ice crystal microstructure during creep experiments

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