Anelastic Straining in Polycrystalline Iceby David M. Cole, U.S. Army Cold Regions Research and, Engineering Lab, Hanover, United States,
Abstract: This paper presents experimental observations on the influence of stress, grain size and total strain level on the magnitude of anelastic strain in granular freshwater ice. Cyclic loading experiments carried out at low total strain levels indicate that the anelastic strain is a function of grain size. Strain recovery experiments, wherein the specimens were deformed to strains as high as 0.07, indicate that the anelastic strain reaches a maximum value at relatively low total strain levels and thereafter remains relatively constant. The results indicate for a given ice type, that when the total strain level is relatively high (e.g. > 0.01), the anelastic strain is no longer a function of grain size, but only of temperature and stress level. A nonlinear relationship between the anelastic strain and applied stress level emerged for the strain recovery experiments. A dislocation-based model that explains the stress dependency is developed and is seen to represent the experimental observations reasonably well. The grain size dependency of the internal friction is explained qualitatively in terms of the structure of grain boundaries. Discussions center on the development of a unified dislocation-based view of the anelastic strain observed under all experimental conditions.
Subject Headings: Grain (material) | Thermal loads | Ice loads | Fresh water | Cyclic loads | Stress strain relations
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