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Author Durham, W. B. ♦ Stern, L. A. ♦ Kirby, S. H.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ PHYSICS ♦ GEOSCIENCES ♦ ICE ♦ RHEOLOGY ♦ STRESS ANALYSIS ♦ PRESSURE DEPENDENCE ♦ PHASE TRANSFORMATIONS ♦ X-RAY DIFFRACTION ♦ MECHANICAL PROPERTIES ♦ DEFORMATION ♦ EXPERIMENTAL DATA
Abstract We have measured the mechanical strength ({sigma}) of pure water ices V and VI under steady state deformation conditions. Constant displacement rate compressional tests were conducted in a gas apparatus at confining pressures from 400 < P < 800 MPa, temperatures from 209 < T < 270 K, and strain rates 7 x 10{sup {minus}7} < & < 7 x 10{sup {minus}4} s{sup {minus}1}. Most of the results fit to an empirical flow law of the form & = A {sigma}{sup n} exp (-E + PV)/RT, where the four material constants A, n, E, and I/* are (for & in inverse seconds and P and {sigma} in megapascals) 10{sup 23,0}, 6.0, 136 kJ/mol, and 29 cm{sup 3}/mol, respectively, for ice V; and 10{sup 6,7}, 4.5, 66 kJ/mol, and 11 cm{sup 3}mol, respectively, for ice VI. Ice VI may weaken to a mechanism of higher E at T > 250 K. Ices V and VI are thus rheologically distinct but by coincidence have approximately the same strength under the conditions chosen for these experiments. To avoid misidentification, these tests are therfore accompanied by careful observations of the occurrences and characteristics of phase changes. One sample each of ice V and VI was quenched at pressure to metastably retain the high-pressure phase and the acquired deformation microstructures; X ray diffraction analysis of these samples confirmed the phase identification. Surface replicas of the deformed and quenched samples suggest that ice V probably deforms largely by dislocation creep, while ice VI deforms by a more complicated process involving substantial grain size reduction through recrystallization. 25 refs., 10 figs., 3 tabs.
ISSN 01480227
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-02-10
Publisher Place United States
Journal Journal of Geophysical Research
Volume Number 101
Issue Number B2


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