Microstructure mapping: a new method for imaging deformation-induced microstructural features of ice on the grain scale

Kipfstuhl, Sepp; Hamann, Ilka; Lambrecht, Anja; Freitag, Johannes; Faria, Sérgio H.; Grigoriev, D. Yu.; Azuma, Nobuhiko

doi:10.3189/172756506781828647

Cited by 68 publications

(123 citation statements)

References 34 publications

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“…This process is very efficient in ice due to the natural deformation conditions of this mineral, i.e. temperatures close to its pressure melting point and deformation at low strain rates (Kipfstuhl et al, 2006). These are observable especially in comparison with fast artificial deformation in creep tests (Weikusat et al, 2009).…”

Section: Introductionmentioning

confidence: 91%

Full-field predictions of ice dynamic recrystallisation under simple shear conditions

Llorens

Griera

Bons

et al. 2016

Earth and Planetary Science Letters

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Understanding the flow of ice on the microstructural scale is essential for improving our knowledge of large-scale ice dynamics, and thus our ability to predict future changes of ice sheets. Polar ice behaves anisotropically during flow, which can lead to strain localisation. In order to study how dynamic recrystallisation affects to strain localisation in deep levels of polar ice sheets, we present a series of numerical simulations of ice polycrystals deformed under simple-shear conditions. The models explicitly simulate the evolution of microstructures using a full-field approach, based on the coupling of a viscoplastic deformation code (VPFFT) with dynamic recrystallisation codes. The simulations provide new insights into the distribution of stress, strain rate and lattice orientation fields with progressive strain, up to a shear strain of three. Our simulations show how the recrystallisation processes have a strong influence on the resulting microstructure (grain size and shape), while the development of lattice preferred orientations (LPO) appears to be less affected. Activation of non-basal slip systems is enhanced by recrystallisation and induces a strain hardening behaviour up to the onset of strain localisation and strain weakening behaviour. Simulations demonstrate that the strong intrinsic anisotropy of ice crystals is transferred to the polycrystalline scale and results in the development of strain localisation bands than can be masked by grain boundary migration. Therefore, the finite-strain history is non-directly reflected by the final microstructure. Masked strain localisation can be recognised in ice cores, such as the EDML, from the presence of stepped boundaries, microshear and grains with zig-zag geometries.

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Section: Introductionmentioning

confidence: 91%

Full-field predictions of ice dynamic recrystallisation under simple shear conditions

Llorens

Griera

Bons

et al. 2016

Earth and Planetary Science Letters

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“…Thin sections were prepared according to standard procedures, allowing the surfaces to sublimate and reveal (sub)grain boundaries as etch grooves (Kipfstuhl and others, 2006). For each sample, at least two sections, one cut horizontally and the other vertically, were prepared.…”

Section: Observation Methodsmentioning

confidence: 99%

“…4b). Kipfstuhl and others (2006) showed that subgrain boundaries are revealed as grooves under controlled sublimation conditions. The dependence of sublimation/thermal grooving on misorientation was described generally by Mullins (1957) and by Saylor and Rohrer (1999) for ceramic polycrystals.…”

Section: Grain-shape Datamentioning

confidence: 99%

“…9). The heterogeneous distribution can be described as a 'core and mantle' structure (Kipfstuhl and others, 2006); a mantle describing the rim of the crystal with high subgrain-boundary density and the core defined by low subgrain-boundary density in the middle of a grain. This description holds for most grains.…”

Section: Distribution Of Subgrain Boundaries Within Grainsmentioning

confidence: 99%

“…Recently, high-resolution crystallographic analysis has provided new information that improves our understanding of recrystallization processes (Montagnat and others, 2003;Miyamoto and others, 2005;Obbard and others, 2006b). For statistical observations at high spatial resolution, a new microstructure-mapping method (Kipfstuhl and others, 2006) allows more direct and easily obtainable observations of features produced by the deformation-related processes. In the future, comparing data obtained using this method for ice-core samples, with unknown deformation conditions, with data obtained in the same way for experimentally deformed ice, with wellknown deformation conditions, may add to our understanding of flow laws in ice sheets.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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The constant‐hardness creep compliance of polycrystalline ice

Caswell

Cooper

Goldsby

2015

Geophysical Research Letters

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We have performed creep and stress‐reduction experiments on polycrystalline ice (grain sizes, d ≈ 30 and ≈ 245 µm) in the grain boundary sliding and dislocation creep regimes (stresses σ = 0.5–5 MPa, temperature T = 233 K) to determine the constant‐hardness creep compliance under these conditions. Our results are consistent with a microstructural state‐variable description of dislocation‐effected deformation whose rate is accelerated by grain boundary sliding. The fine‐grained specimens reveal no subgrain boundaries, indicating that the stress‐sensitive microstructural feature upon which the state‐variable behavior is founded may be the dislocation structure of the grain boundaries. Deviations of our constant‐hardness data from the behavior predicted by the state‐variable formulation allow estimation of the viscosity of the grain boundaries, which is ~4.8 × 106 Pa s at this temperature.

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Microstructure mapping: a new method for imaging deformation-induced microstructural features of ice on the grain scale

Cited by 68 publications

References 34 publications

Full-field predictions of ice dynamic recrystallisation under simple shear conditions

Full-field predictions of ice dynamic recrystallisation under simple shear conditions

Evolution of ice crystal microstructure during creep experiments

The constant‐hardness creep compliance of polycrystalline ice

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