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  • 1
    Electronic Resource
    Electronic Resource
    Viscous Response of Polar Ice with Evolving Fabric (1998)
    Springer
    Continuum mechanics and thermodynamics 10 (1998), S. 135-152 
    Details
    ISSN: 1432-0959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Re-orientation of individual crystal glide planes as isotropic surface ice is deformed during its passage to depth in an ice sheet creates a fabric and associated anisotropy. A simple macroscopic description is that these material glide planes are rotated towards planes normal to an axis of compression, and away from planes normal to an axis of extension, inducing an instantaneous orthotropic viscous response with reflexional symmetries in the planes orthogonal to the current principal stretch axes. An associated orthotropic viscous law expresses the stress in terms of the strain-rate, deformation, and three structure tensors based on the principal stretch axes. General frame indifferent forms are analysed to determine the fabric induced during differential stretchings along fixed principal axes. Then, freezing the fabric by removal of the stress, and hence strain-rate, the instantaneous simple shear responses in different planes are determined and compared. The corresponding instantaneous viscosities are expressed in terms of the response coefficients of the constitutive model. A simple model is adopted to illustrate the evolution of the viscosities during axial stretchings and shearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001610050086
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Orthotropic viscous response of polar ice (2000)
    Springer
    Journal of engineering mathematics 37 (2000), S. 191-209 
    Details
    ISSN: 1573-2703
    Keywords: polar ice ; induced anisotropy ; orthotropy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Re-orientation of individual crystal glide planes as isotropic surface ice is deformed during its passage to depth in an ice sheet creates a fabric and associated anisotropy. A simple macroscopic description is that these material glide planes are rotated towards planes normal to an axis of compression, and away from planes normal to an axis of extension, inducing an instantaneous orthotropic viscous response with reflexional symmetries in the planes orthogonal to the current principal stretch axes. An associated orthotropic viscous law expresses the stress in terms of the strain-rate, strain, and three structure tensors based on the principal stretch axes. The fabric induced during differential stretchings along fixed principal axes, and the subsequent instantaneous viscous shear response in different planes due to the frozen fabric when the axial stress and strain-rate are removed, define a set of instantaneous directional viscosities in terms of the frozen principal stretches and the material response coefficients. Various inequalities and equalities between these viscosities are derived from the original rotation concepts, which, together with observed enhancement factors at large stretch and shearing, impose restrictions on the permitted response coefficients. It is shown how a simple viscous law can meet all these requirements, and such a law is illustrated for continued axial stretchings and shearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004738429373
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  • 3
    Electronic Resource
    Electronic Resource
    A finite-element treatment of sea ice dynamics for different ice rheologies (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 153-174 
    Details
    ISSN: 0363-9061
    Keywords: finite-element ; sea ice pack ; rheology ; viscous-plastic ; viscous fluid ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: In this paper the effects of four different rheologies on the evolution of a large-scale sea ice pack are determined and compared. Two rheologies are of viscous-plastic form, and two are viscous fluid relations. The initial pack domain is rectangular, and the motion is driven by wind stress and resisted by ocean drag. Two adjacent edges are rigid shore boundaries, and the other two are free boundaries at open water which move during the pack motion, so that the pack domain changes in time. Two different forms of boundary conditions at the rigid shore edges are considered, which also influence the evolution. The governing equations are solved numerically using a finite-element method, and, unlike previous numerical treatments, no artificial viscosity is incorporated to stabilise the algorithm near interfaces between converging and diverging flow. Instability arises when any tensile stress is abruptly cut-off when diverging flow is initiated, and an alternative view is offered. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Uni-axial wave propagation and pore pressure generation in fluid saturated sands exhibiting irreversible compaction (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 695-720 
    Details
    ISSN: 0363-9061
    Keywords: wave propagation ; compaction ; pore pressure generation ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The propagation of a plane load-unload pulse through a compacting sand is analysed and illustrated for both dry sand and liquid saturated sand in undrained conditions. A major feature is the interaction between the initial loading wave and the faster following unloading wave. Free draining and undrained conditions exhibit distinct qualitative and quantitative results, and the pore liquid pressure generation is a significant physical feature. Illustrations show the effects of different applied surface pulse shapes. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
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    Two orthotropic models for strain-induced anisotropy of polar ice (1999)
    Cambridge University Press
    Details
    Publication Date: 1999-01-01
    Description: As polar ice descends from the free surface to depth in a large ice sheet, it undergoes deformations which give rise to the formation and subsequent evolution of a fabric and associated anisotropy. In this paper two orthotropic models of such strain-induced anisotropy are considered. Model A is based on analysis of the microscopic behaviour of an individual ice crystal with transversely isotropic response and assumed uniform stress in a polycrystal. The macroscopic response of the ice aggregate is then derived by applying the concept of an orientation distribution function, and the resulting viscous law relates the strain rate to the stress and three structure tensors. In model B it is assumed that the macroscopic response of ice is determined by the fabric induced entirely by macroscopic deformations, and all microprocesses taking place at the grain level are ignored. A constitutive relation is derived from a general frame-indifferent law for orthotropic materials, and expresses the stress in terms of the strain rate, strain and throe structure tensors. The two models are applied to determine the viscous response of ice to continued uniaxial compression and simple shearing in order to compare the predictions of both theories.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 6
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    Two orthotropic models for strain-induced anisotropy of polar ice (1999)
    Cambridge University Press
    Details
    Publication Date: 1999-01-01
    Description: As polar ice descends from the free surface to depth in a large ice sheet, it undergoes deformations which give rise to the formation and subsequent evolution of a fabric and associated anisotropy. In this paper two orthotropic models of such strain-induced anisotropy are considered. Model A is based on analysis of the microscopic behaviour of an individual ice crystal with transversely isotropic response and assumed uniform stress in a polycrystal. The macroscopic response of the ice aggregate is then derived by applying the concept of an orientation distribution function, and the resulting viscous law relates the strain rate to the stress and three structure tensors. In model B it is assumed that the macroscopic response of ice is determined by the fabric induced entirely by macroscopic deformations, and all microprocesses taking place at the grain level are ignored. A constitutive relation is derived from a general frame-indifferent law for orthotropic materials, and expresses the stress in terms of the strain rate, strain and throe structure tensors. The two models are applied to determine the viscous response of ice to continued uniaxial compression and simple shearing in order to compare the predictions of both theories.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 7
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    Plane ice-sheet flow with evolving orthotopic fabric (2000)
    Cambridge University Press
    Details
    Publication Date: 2000-01-01
    Description: A plane, gravity-driven, steady flow of an isothermal ice sheet over a horizontal bedrock, with no-slip basal conditions, is considered. The ice is modelled as a linearly viscous, incompressible and anisotropic fluid, with evolving orthotropic fabric that depends on local strain rates and deformations. For a fixed, free-surface elevation, the ice-accumulation rates necessary to maintain the prescribed geometry are calculated by using the finite-element method, together with the velocities and stresses. Numerical simulations have been carried out for different combinations of enhancement factors for compression and shear in order to investigate their effect on the rate of flow. The results obtained have shown that, apart from the near-divide region, the global flow rate is nearly proportional to the magnitude of the shear-enhancement factor and is very little sensitive to the value of the compression enhancement factor. Normalized velocity-depth profiles have been compared for the anisotropic and isotropic ice and it has been found that significant differences occur only in a region near the ice divide. Direct shear stresses are little affected by the ice anisotropy, but the longitudinal deviatoric stresses in a part of the ice sheet are significantly increased compared to the isotropic ice flow.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 8
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    Uni-axial wave propagation and pore pressure generation in fluid saturated sands exhibiting irreversible compaction (1998)
    Wiley
    Details
    Publication Date: 1998-09-01
    Print ISSN: 0363-9061
    Electronic ISSN: 1096-9853
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Published by Wiley
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  • 9
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    A finite-element treatment of sea ice dynamics for different ice rheologies (1998)
    Wiley
    Details
    Publication Date: 1998-03-01
    Print ISSN: 0363-9061
    Electronic ISSN: 1096-9853
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Published by Wiley
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