Shortt, M; Sammonds, P; (2020) Experiments on the Micromechanics of Ice using Scanning Electron Microscopy. In: Proceedings of the 25th International Conference on Port and Ocean Engineering under Arctic Conditions. POAC: Delft, The Netherlands.

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Abstract

From both geophysical and engineering perspectives, a comprehensive characterisation of the micromechanical behaviour of ice is desirable. The deformation of ice observed on larger scales, both in the field and laboratory, is controlled by the underlying microstructure of the ice, as well as internal defects incorporated into the microstructure. Thus, to fully understand the deformation behaviour of the sea ice cover across the Arctic Basin, or at a more local scale, interactions between sea ice floes and offshore structures, knowledge of the microstructure of the ice, and its micromechanical response under applied stresses are imperative. We have developed an experimental methodology for in-situ mechanical testing of millimetre-scale ice samples within the chamber of a scanning electron microscope (SEM). This enables the measurement of the stress-strain behaviour of the ice as well as simultaneous real-time imaging of the surface topography, providing a visual indication of the micromechanical processes occurring during deformation. In this paper, we give a description of the experimental methodology, followed by results from preliminary compression tests on freshwater ice samples. Prior to testing, the surface of each sample was imaged, revealing microstructural features such as grain boundaries. Stress-strain curves were obtained for each test in addition to videos of the SEM display during deformation. The SEM imaging revealed various deformation features during the tests, most notably crack initiation and propagation and the eventual failure of the samples. Applying this methodology to saline ice, in conjunction with concurrent mechanical tests on larger scales, we aim to establish empirical scaling relations for sea ice mechanics. These results may then be implemented into basinscale sea ice models as well as models for ice-structure interactions.

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