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The Micromechanisms of Flow and Fracture of Ice

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Final rept. 12 Jul 2000-11 Jul 2001

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The overall goals of this work were to relate the microstructure, including the defect structure and impurity content and location, to the mechanical and physical properties of ice. Research focused on determining the structure and microstructural location of impurities in natural ice using a scanning electron microscope equipped with a cold stage and x-ray microanalysis. Thus, for the first time, the microstructure and microchemistry of pond and river ice was characterized at high resolution less than 1 micrometer. Samples were produced from cores harvested during January and February 2001, February 2002, and February and March 2003 from the Lower Baker Pond Wentworth-Orford, New Hampshire. Ice from the Connecticut River Hanover, New Hampshire also was collected in February 2001. Preliminary mechanical testing was performed on the pond ice, including studies of its brittle compressive strength through a series of uniaxial and biaxial compression experiments at -10 degrees C. using a triaxial MTS servo-hydraulic system. The effects of impurities on the creep of high-purity single ice crystals and single crystals doped with sulfuric acid also were studied. The experiments demonstrated that both undoped and doped ice crystals were capable of undergoing large deformations with strains in excess of 200 percent. Equal channel angular extrusion was used to examine the effects of impurities on the recrystallization of single crystal ice. Preliminary electrical measurements were performed on sulfuric acid-doped ice, which demonstrated dramatic differences in the resistivity of the lattice and grain boundaries. Lastly, the authors developed a technique that does not require the prior application of a conductive metal coating to study the structure of snow crystals using a scanning electron microscope and a cold-stage. 7 figures

Subject Categories:

  • Snow, Ice and Permafrost
  • Crystallography

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