Under high hydrostatic pressure combined with shear, the structure of poly crystalline ice breaks down into fine-grained material by a process of recrystallization. Accompanying this process is a substantial softening of the material. Measurements of activation energy at low strains prior to the breakdown of structure, at temperatures of -10°C, show an increase of activation energy from about 80 kJ mol~(-1) to about 120k kJ mol~(-1) as the pressure increases, with values at about 70 MPa similar to those found by other researchers for temperatures between -10 and 0°C. These results suggest that grain boundary effects might result in the increased strain rates. The various energies that might drive the subsequent recrystallization process have been investigated. The results suggest strongly that elastic strain energy is the driving force in the process.
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