Tertiary creep damage model for polycrystalline ice
A continuum damage model for the temperature dependent creep response of polycrystalline ice under a multiaxial state of stress, suited for ice in polar regions, is developed. The proposed model is based on a thermo-viscoelastic constitutive law for ice creep and a local orthotropic damage accumulation law for tension, compression and shear loadings. Orthotropic damage is represented by a symmetric second-order damage tensor and its effect on creep is incorporated through the effective stress concept. The unknown model parameters are first calibrated using published experimental data from constant uniaxial stress tests under pure compressive and pure tensile loadings; and then, predictions are made for constant strain rate and multiaxial loadings. The predicted results are in good agreement with both experimental and numerical results in the literature illustrating the viability of the proposed model. The model captures the temperature dependence of material strength and asymmetric mechanical behavior under tension and compression. The model is mainly intended for studying the failure mechanisms of polar ice at low deformation rates with depth varying temperature profiles.Model fit to experimental data and parameter calibration. Figures a and b show the asymmetric behavior of ice under pure compressive and tensile loadings. Figure c shows the temperature dependence of material behavior of ice.