Author(s): Jun Li; T. H. Jacka
Linked Author(s):
Keywords: No Keywords
Abstract: It has been established for 4 decades that a power flow law with exponent, n = 3 well describes the creep deformation of isotropic ice for minimum strain rate or secondary creep (Glen 1958). This law has been experimentally developed through deformation tests in simple stress configurations (eg: simple shear, uniaxial compression). Recent work (Li and others, 1996) has established that for constant octahedral stress (root mean square of the principal stress deviators), the minimum isotropic octahedral shear strain rate has no dependence on stress configuration. This was established by conducting a series of tests under the same octahedral stress, but with the stress magnitude made up of different ratios of shear to compression. A series of tests presented in this paper again with a variety of ratios of shear to compression, includes a range of different octahedral stress magnitude, thus allowing examination of the power law exponent. Octahedral shear stresses ranged between 0.20 and 0.89 MPa. All tests were run to beyond minimum creep. Results show that isotropic minimum octahedral shear strain rate increases with increasing octahedral shear stress according to the power flow law with an exponent of 3. This octahedral strain rate-stress relation is in good agreement with that obtained from the simple stress configuration, adding support to the fundamental assumption (Nye 1953, Glen 1958) that for isotropic ice flow the second invariant of strain rate is dependent only on the second invariant, of the stress tensor.
Year: 1996