Modeling the Transient Creep Behavior of Polycrystalline ice with an Elasto-viscoplastic Homogenization Scheme
Abstract
The flow of the large Greenland and Antarctica ice sheets is largely controlled by the rheology of the ice. Ice deforms in-situ at very high temperature as compared to the melting point (T/Tf >= 0.8) and in a quasi-static regime that can be described by a non-linear viscoplastic constitutive relation. However, the interpretation of mechanical tests performed in the laboratory requires a better understanding of all creep regimes. Upon instantaneous loading, the stress is almost uniformly distributed inside the polycrystalline ice sample owing to the quasi-isotropic elastic behavior of ice crystals. But as deformation proceeds, the load is gradually transferred to the grains that are badly oriented for intracrystalline (dislocation) slip owing to the very large viscoplastic anisotropy of ice crystals. The decrease of strain rate during the transient creep by more than two orders of magnitude is associated with large directional internal stresses. Secondary creep has a rather short existence because it is immediately followed by the tertiary creep associated with discontinuous recrystallization that initiates systematically after 1.% total strain. This secondary creep regime is often considered as a stationary regime. Modeling the transient (up to the secondary) creep behavior of polycrystalline ice requires to account for the ``long term memory effect'' resulting from the elasto-viscoplastic coupling, together with the non-linear and strongly anisotropic viscoplastic behavior. This can be achieved by the recently developed affine self-consistent homogenization scheme, which allows the description of the overall mechanical behavior of the aggregate with respect to the local elastic and viscoplastic behavior of the grains. Comparison of model results to a large set of experimental data will be given.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.C61A..09C
- Keywords:
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- 1863 Snow and ice (1827);
- 3210 Modeling;
- 5120 Plasticity;
- diffusion;
- and creep;
- 8160 Rheology: general