Analysis of Dynamic Recrystallization of Ice from EBSD Orientation Mapping

Montagnat, Mâurine; Chauve, Thomas; Barou, Fabrice; Tommasi, Andréa; Beausir, Benoît; Fressengeas, Claude

doi:10.3389/feart.2015.00081

Cited by 45 publications

(88 citation statements)

References 64 publications

(94 reference statements)

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“…Dynamic recrystallisation affects the evolution of the microstructure (grain-size and shape) and influences the development of LPOs (e.g. Montagnat et al, 2015). This process is very efficient in ice due to the natural deformation conditions of this mineral, i.e.…”

Section: Introductionmentioning

confidence: 99%

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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: 99%

“…or from experiments of natural or artificial ice deformed in the laboratory (Azuma, 1994;Treverrow et al, 2012;Montagnat et al, 2015). However, ice experiments in the laboratory are performed at high strain rates compared with that in natural conditions (Budd and Jacka, 1989) and high finite strains cannot be achieved.…”

Section: Introductionmentioning

confidence: 99%

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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“…Grain boundaries surrounding new small grains can appear more irregular than in reality because of intrinsic limitation of the AITA observation based on thin sections (about 0.3 mm thick). A lot of sub-grain boundaries similar to the tilt and kink bands characterized in Chauve et al (2015Chauve et al ( , 2017 are visible after deformation. A tilt band is composed of basal edge dislocations and can accommodate a large misorientation, as observed here.…”

Section: Stress Temperaturementioning

confidence: 91%

“…1). Details of the procedure for sample preparation can be found in Grennerat et al (2012) and Chauve et al (2015).…”

Section: Methodsmentioning

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.…”

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confidence: 99%

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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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Insights into anisotropy development and weakening of ice from in situ P wave velocity monitoring during laboratory creep

et al. 2017

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Polycrystalline ice weakens significantly after a few percent strain, during high homologous temperature deformation. Weakening is correlated broadly with the development of a crystallographic preferred orientation (CPO). We deformed synthetic polycrystalline ice at −5°C under uniaxial compression, while measuring ultrasonic P wave velocities along several raypaths through the sample. Changes in measured P wave velocities (Vp) and in the velocities calculated from microstructural measurements of CPO (by cryo‐electron backscatter diffraction) both show that velocities along trajectories parallel and perpendicular to shortening decrease with increasing strain, while velocities on diagonal trajectories increase. Thus, in these experiments, velocity data provide a continuous measurement of CPO evolution in creeping ice. Samples reach peak stresses after 1% shortening. Weakening corresponds to the start of CPO development, as indicated by divergence of P wave velocity changes for different raypaths, and initiates at ≈3% shortening. Selective growth by strain‐induced grain boundary migration (GBM) of grains favorably oriented for basal slip may initiate weakening through the formation of an interconnected network of these grains by 3% shortening. After weakening initiates, CPO continues to develop by GBM and nucleation processes. The resultant CPO has an open cone (small circle) configuration, with the cone axis parallel to shortening. The development of this CPO causes significant weakening under uniaxial compression, where the shear stresses resolved on the basal planes (Schmid factors) are high.

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Analysis of Dynamic Recrystallization of Ice from EBSD Orientation Mapping

Cited by 45 publications

References 64 publications

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

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

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

Insights into anisotropy development and weakening of ice from in situ P wave velocity monitoring during laboratory creep

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