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| Deformation maps describing mechanisms through which ice deforms have been calculated by Goodman et al. (1981), Frost & Ashby (1982), Duval et al. (1983) and Ashby & Duval (1985). The maps show the region, within stress-temperature space, where one of the flow mechanisms is dominant. Maps are generally plotted with the microscale variables, including grain size, held as constants. The upper boundary of the maps is defined by the region of brittle failure for ice. The diagram below shows deformation maps for the grain sizes 0.1mm, 1mm and 10mm. Diffusional flow and glide controlled flow form two broad classes of mechanisms through which ice deforms. Lines of strain rate are also mapped onto the diagrams. The strain rate for each component is calculated from the respective steady state flow laws. As diffusional flow and glide mechanisms occur concurrently the maps show the total strain rate:
The maps have three major regions: a low stress region dominated by diffusional flow; a moderate stress region where glide controlled creep dominates; and a high temperature - high stress area dominated by pressure melting. At high temperatures both recrystallisation and grain boundary melting contribute to the deformation. |
| Figure 2. 17. 1 Deformation mechanism maps
for isotropic polycrystalline ice by Goodman et al. (1981). The fields
show the deformation process that dominates, given the temperature and
stress conditions, and do not indicate that these are the only processes
active. The strain rate contours represent the cumulative strain for all
processes contributing to deformation. Each contour represents one order
of magnitude in |
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Created: August 23, 1999 Last modified: March 15, 2004 Authorised by: Head, School of Earth Sciences Property of School of Earth Sciences - The University of Melbourne - Australia. Disclaimer and copyright. Design and maintained by Hadi Sim (hadims@unimelb.edu.au) |