X-Ray Topographic Studies of Dis1ocation/Grain Boundary Interactions in Ice.
Final rept. 1 Mar 93-30 Aug 96,
THAYER SCHOOL OF ENGINEERING HANOVER NH
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The interaction of dislocations with grain boundaries in polycrystalline ice have been studied using in situ deformation sychrotron x-ray topography. Specimen preparation was performed in the Ice Research Laboratory at Dartmouth College, and x-ray topography was performed at the National Sychrotron Light Source at Brookhaven National Laboratory, in collaboration with Prof. M. Dudley SUNY at Stony Brook and Dr. D. Black NIST. We have demonstrated that x-radiation can be used to study ice without affecting the dislocations present. The main part of the work has demonstrated that normally basal dislocations are emitted from grain boundary facets during grain boundary sliding. However, in situations where basal slip is suppressed, by having no resolved shear stresses on the basal plane, non-basal slip occurs. Normally, dislocations are emitted into both adjacent grains from a grain boundary facet, glide across the grain and pile-up at the opposite boundary. However, it has been demonstrated that these pile-ups can lead to slip transmission for certain geometrical arrangements of the basal planes, on either side of the grain boundary. The project also briefly explored dislocation behavior ahead of loaded notches in single crystals, and the effect of high concentrations of HCl on the velocity of dislocations.
- Snow, Ice and Permafrost