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

Chauve, Thomas; Montagnat, Mâurine; Lachaud, Cédric; Georges, David; Vacher, Pierre

doi:10.5194/se-8-943-2017

Cited by 13 publications

(8 citation statements)

References 40 publications

(66 reference statements)

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“…The interaction between the moving dislocations and the new grain boundaries probably contributed to the development of these defects. Deformation experiments combining high-resolution digital image correlation and EBSD in metals (Harte et al, 2020) or ice (Chauve et al, 2017b) have shown evidence for a local increase in lattice distortion (misorientation) on a scale of few micrometres from grain boundaries. Post-mortem studies using high angular resolution EBSD (Guo et al, 2014;Larrouy et al, 2015) and in situ deformation TEM experiments (Kondo et al, 2016) showed that when there is poor alignment between the slip system of the incoming dislocation and the easy slip systems in the adjacent grain, grain boundaries block the slip transfer either partially or completely, producing dislocation pile-ups and stress concentrations.…”

Section: From Subgrain (Labs) To Grain Boundaries (Hagbs)mentioning

confidence: 99%

Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

et al. 2021

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We document how dynamic recrystallization by subgrain rotation (SGR) develops in natural olivine-rich rocks deformed in extension to up to 50% bulk finite strain (1473 K, confining pressure of 300 MPa, and stresses between 115 and 180 MPa) using electron backscatter diffraction (EBSD) mapping. SGR occurs preferentially in highly deformed grains (well-oriented to deform by dislocation glide) subjected to local stress concentrations due to interactions with hard neighboring grains (poorly-oriented olivine crystals or pyroxenes). Subgrains (misorientation <15 • ) are mainly delimited by tilt walls composed of combinations of dislocations of the [100] (001), [001](100), [100](010) and [001](010) systems, in order of decreasing frequency. The activation and prevalence of these systems agree with a Schmid factor analysis using data for high-T dislocation creep in olivine. The development of closed 3D subgrain cells by SGR recrystallization requires the contribution of at least three different slip systems, implying the activation of hard slip systems and high (local) stresses. The transition from subgrain to grain boundaries (misorientation ≥15 • ) is characterized by a sharp change in the misorientation axes that accommodate the difference in orientation between the two subgrains or grains. We propose that this change marks the creation and incorporation of new defects (grain boundary dislocations with different Burger vectors and, likely, disclinations or disconnections) at the newly-formed grain boundaries and that this might be favoured by stress concentrations due to increasing misalignment between slip systems across the boundary. Finally, we document the development of strong misorientations within the parent grains, due to the accumulation of low angle grain boundaries, and between them and the recrystallized grains. SGR recrystallization may thus produce strong dispersion of the crystal preferred orientation without the need for grain boundary sliding.

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Section: From Subgrain (Labs) To Grain Boundaries (Hagbs)mentioning

confidence: 99%

Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

et al. 2021

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“…Indeed, recent experimental observations have (i) clearly documented the role of the crystal viscoplastic anisotropy in generating local stresses and strains markedly different from the macroscopic ones [3,32,66] and (ii) revealed that the formation of new orientations (nucleation) during dynamic recrystallization occurs through bulging (heterogeneous grain boundary migra- tion) and polygonization (formation of new grains boundaries by organization of dislocations within a grain) [3,33,63,66,73]. These two processes are controlled by the local strain and stress fields and result in recrystallized orientations that are strongly related to, but slightly different from, the parent grain orientations.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, microcracking is also expected to have occurred in Qi et al 2017 [30] experiments. Strong stress concentration occurs at crack tips, and Chauve et al 2017 [73] have recently shown that, for ice, this stress concentration can be released through DRX. The R 3 iCe formulation does not account for microcracking or the effect of confining pressure.…”

Section: Discussionmentioning

confidence: 99%

A physically-based formulation for texture evolution during dynamic recrystallization. A case study of ice

Chauve,

Montagnat,

Dansereau

et al. 2024

Comptes Rendus. Mécanique

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Dynamic recrystallization can have a strong impact on texture development during the deformation of polycrystalline materials at high temperatures, particularly for materials with strong viscoplastic anisotropy such as ice. Owing to this anisotropy, recrystallization is essential for ensuring strain compatibility, and the development of textures leads to anisotropic softening. Accurate prediction of the effect of recrystallization on the texture evolution of ice is therefore crucial to adequately account for texture-induced mechanical anisotropy in large-scale models of glacial ice flow. However, this prediction remains a challenge.We propose a new formulation for modeling texture evolution due to dynamic recrystallization on the basis of observations of the evolution of the microstructure and texture of ice deforming by dislocation creep and dynamic recrystallization. This formulation relies on an orientation attractor that maximizes the resolved shear stress on the easiest slip system in the crystal. It is implemented in the equation describing the evolution of the crystal orientation with deformation and is coupled with an anisotropic viscoplastic law that provides the mechanical response of the ice crystal. This set of equations, which is the core of the R 3 iCe model is solved by a finite-element method with a semi-implicit scheme coded using the Rheolef library. The resulting open-source software R 3 iCe is validated by comparison with laboratory creep data for ice polycrystals under uniaxial compression, simple shear, and uniaxial tension. It correctly reproduces the texture evolution and mechanical softening observed in the experiment during tertiary creep. Although the

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“…DIC imaging of uniaxial compression creep tests in columnar ice at -7 and -10°C, 0.5 MPa to higher bulk strains showed that nucleation occurred mainly at triple junctions and along boundaries between grains with markedly different orientations, highlighting a relation between local strain incompatibility and dynamic recrystallization (Chauve et al, 2015;Piazolo et al, 2015). Grain-scale strain incompatibility also played an essential role in strain localisation at the brittle-plastic transition, where dynamic recrystallization and fracturing are coupled (Chauve et al, 2017b).…”

Section: Introductionmentioning

confidence: 96%

Decoupling between strain localisation and the microstructural record revealed by in-situ strain measurements in polycrystalline ice

López-Sánchez¹,

Chauve²,

Montagnat³

et al. 2023

Preprint

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We explore the links between the evolutions of the strain field and microstructure in coarse-grained Ih ice. Using digital image correlation (DIC), we monitored the evolution of the strain field in two columnar ice samples deformed by creep (uniaxial compression at constant load) at -7 ºC and 0.5 MPa up to 9.5% bulk shortening. After a brief transient (<0.2% bulk strain), in which strain localises nearby grain boundaries, viscoplastic strain concentrates in a few narrow intracrystalline shear bands that eventually extend over multiple grains. Comparison of pre and post-deformation crystal orientation maps shows that strain localisation in shear bands is mainly accommodated by basal glide without creating significant dislocation-related substructures. Severe dynamic recrystallization develops locally at grain boundaries that act as barriers to dislocation motion, especially where transfer of basal shear is ineffective. Full-field simulations reproducing the initial microstructure and experimental setup suggest that dynamic recrystallization is preferentially triggered at locations characterized by high work rates. Overall, these observations indicate that during deformation of coarse-grained Ih ice at high homologous temperatures and fast (experimental) strain rates: (1) recrystallization does not drive strain localisation but accommodates strain incompatibility and (2) large strains can be accommodated by unimpeded basal slip without producing dislocation concentrations. Observation (2) implies that intragranular orientation gradients are unreliable gauges of viscoplastic strain intensity and that the proportion of dislocation types in subgrains does not gauge the relative contribution of different slip systems to deformation.

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

Cited by 13 publications

References 40 publications

Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

Dynamic recrystallization by subgrain rotation in olivine revealed by electron backscatter diffraction

A physically-based formulation for texture evolution during dynamic recrystallization. A case study of ice

Decoupling between strain localisation and the microstructural record revealed by in-situ strain measurements in polycrystalline ice

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