Simulation of uniaxial compression tests using Taylor-type models in which crystal rotation and recrystallization processes are included (Abstract)
Physics of Ice Core Records, Edited by T. Hondoh, Hokkaido University Press, p. 117, Sapporo 2000
D. Dahl-Jensen
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.
T. Thorsteinsson
Alfred-Wegener-Institut für Polar- und Meeresforschung, Sektion Geophysik, Postfach 120161, D-27515 Bremerhaven, Germany.
R.B. Alley
Earth System Science Center and Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
ABSTRACT.
Unconfined uniaxial compression tests have been performed on ice from the Summit ice cores in Central Greenland. Ice from three depth have been chosen: isotropic ice from a shallow depth (150 m), ice with a single maximum fabric from 1700 m depth and ice with a very strong single maximum fabric from 2585 m depth. The tests have all been performed at 16 oC with an octahedral stress of 3 bar (vertical stress 6.36 bar).
Five tests have been performed on the ice from each of the three depths in which the direction of the applied compression has been changed from 0 deg to 90 deg relative to the vertical direction in the ice which is the symmetry axis of the crystal fabrics. Most of the tests have reached the tertiary creep regime with after more than 10% strain.
The minimum strain rates vary with more than a factor of 100, while the same tertiary strain rates are reached for the five tests at each depth. A Taylor type model as described by Azuma has been used to simulate the deformation and the rotation of the grains. The variation of the minimum strain rates can be used to determine the flow law parameter in the applied flow law, while the strain rate versus strain creep curves can be used to gain knowledge on the recrystallization process.
The measured fabric is used in the simulations and good agreement is reached between the test results and the model calculations.