Author(s): R. L. Brown; L. R. Mckittrick
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Abstract: Recent experimental results obtained by the authors have shown very large differences between the mechanical properties of single crystals of sea ice and nonsaline ice. This study was undertaken in an effort to determine the reasons for these differences. Several deformation mechanisms were considered as possible sources for the additional compliance of sea ice relative to pure ice. One involves interplatelet slip, while the second was attributed to the reduced rigidity of the ice matrix due to the presence of the brine pockets in sea ice. Finally a third mechanism is associated with increased dislocation sources due to the geometry of the brine pockets. A series of constant deformation rate tests were run on both pure ice and sea ice crystals at temperatures ranging from -10C to -45C in five degree increments so that differences in material response below and above the eutectic temperature could be evaluated. Sharp departures in response could not be detected as the temperature dropped below the eutectic point, thereby indicating that the first mechanism does not play an important role. Calculations were also made to determine the effect of changing brine content on properties, and the variation of this variable on the properties could not explain the differences between the pure ice and sea ice crystal properties. Finally, the effect of stress concentrations associated with the brine pockets was evaluated in a qualitative manner, and this effect was considered to be responsible for most of the difference. Work is continuing to quantify each of these effects.
Year: 1992