Author(s): Stig-Goran Sjolind

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Abstract: A constitutive equation is proposed for describing nonlinear inelastic and brittle behaviour of polycrystalline ice. The influence on mechanical properties of densely distributed microcracks is taken into account in an average sense using principles of continuum damage mechanics. Microcracks are represented with vectorial internal variables. When material symmetry properties are taken into account this leads to damage representation with a set of symmetric second order tensorial variables. The average influence of microcracking on elastic properties are derived from a general expression for the Helmholtz free energy potential. Material parameters describing elastic behaviour are obtained from corresponding results calculated using Hill's self-consistent method and by computer simulation. Inelastic viscous properties are modelled using a generalised creep model of power-law type containing tensorial and scalar internal variables. With these internal variables transient creep, creep recovery and creep hesitation can be modelled. To satisfy a priori the second law of thermodynamics creep rate and evolution equations for the internal variables are derived from convex dissipation potentials defined in spaces spanned by corresponding conjugate thermodynamic force quantities. The proposed constitutive model has been tested on some simple structures in simple stress and strain rate conditions. Numerically obtained results show good agreement with test results.

DOI:

Year: 1990