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Titel |
Computational analysis of dynamic recrystallization of ice aggregates during viscoplastic deformation |
VerfasserIn |
Maria-Gema Llorens, Albert Griera, Ilka Weikusat, Paul Bons, Ricardo Lebensohn, Lynn Evans, Sandra Piazolo |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250107753
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Publikation (Nr.) |
EGU/EGU2015-7466.pdf |
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Zusammenfassung |
Ice is a common mineral at the Earth’s surface. How much ice is stored in the Greenland and
Antarctic ice sheets depends on its mechanical properties. Therefore properties of ice directly
impact on human society through its role in controlling sea level. The bulk behaviour of large
ice masses is the result of the behaviour of the ensemble of individual ice grains. This is
strongly influenced by the viscoplastic anisotropy of these grains and their lattice orientation.
Numerical modelling provides a better insight into the mechanics of ice from the micro to the
ice sheet scale. We present numerical simulations that predict the microstructural
evolution of an aggregate of pure ice grains at different strain rates. We simulate
co-axial deformation and dynamic recrystallization up to large strain using a full-field
approach.
The crystal plasticity code (Lebensohn et al., 2009) is used to calculate the response of a
polycrystalline aggregate that deforms by purely dislocation glide, applying a Fast Fourier
Transform (FFT). This code is coupled with the ELLE microstructural modelling platform to
include intracrystalline recovery, as well as grain boundary migration driven by the reduction
of surface and strain energies.
The results show a strong effect of recrystallization on the final microstructure, producing
larger and more equiaxed grains, with smooth boundaries. This effect does not significantly
modify the single-maximum pattern of c-axes that are distributed at a low angle to the
shortening direction. However, in experiments with significant recrystallization the a-axes
rotate towards the elongation axis at the same time as the c-axes rotate towards the
compression axis. If slip systems on prismatic and/or pyramidal planes are active, it is
thought that a-axes gradually concentrate with depth (Miyamoto, 2005). The bulk activity of
the slip systems is different depending on the relative activity of deformation versus
recrystallization: the non-basal slip systems are more active at high strain in experiments with
dynamic recrystallization compared to those experiments with low recrystallization
activity.
A. Miyamoto, H. Shoji, A. Hori, T. Hondoh, HB. Clausen and O. Watanabe, 2005. Ice
fabric evolution process understood from anisotropic distribution of a-axis orientation on the
GRIP ice core. Annals of Glaciology 42, 47-52.
R. Lebensohn, M. Montagnat, P. Mansuy, P. Duval, J. Meyssonnier and A. Philip, 2009.
Modelling viscoplastic behavior and heterogeneous intracrystalline deformation of columnar
ice polycrystals. Acta Materialia 52, 5347–5361. |
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