Microstructural evolution of ice under simple shear deformation

University essay from Göteborgs universitet/Institutionen för geovetenskaper

Author: Carina Liebl; [2021-01-11]

Keywords: ;

Abstract: To investigate microstructure in ice deformed under simple shear conditions experimentswere performed with artificial polycrystalline ice and natural ice samples form Vatnajökullglacier in Iceland. A new deformation apparatus was tested and results from deformationwere compared to literature to validate the method. Boundary conditions for deformationwere varied. Experiments were performed at -5°C and -10°C and three strain rates wereapplied (2.5x10-7 1/s, 1.25x10-6 1/s, 2.5x10-6 1/s). It is shown that the natural samples,which contain only 2-3 grains, provide a close-up image on specific situation. This gives theopportunity to study them in detail.A special focus is set on the behaviour of grain boundaries during deformation. A preferredarrangement with at least one side of the boundary close to a prism face is seen. While inwarm or slow deformations a tendency to favour boundaries with a combination of {1̅1̅22}and {101̅2} faces. The type of crystall face and their orientation towards deformationdirection befor deformation has an major influence on the development duringdeformation.Brittle fractures were observed in the samples, which immediately filled with small newgrains. This was only observed in samples deformed at -10°C but no dependency to strainrate was oberved.

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