Modeling the cyclic loading response of sea ice

Abstract

This paper describes a physically based model of the elastic and anelastic behavior of sea ice subjected to zero-mean-stress cyclic loading. It incorporates the influence of porosity and fabric. The work demonstrates that despite the complexity of the sea ice microstructure, it is possible to develop links between its physical and mechanical properties through careful experimentation and detailed physical properties measurements.As a consequence of the presence of liquid brine at temperatures of interest, the porosity of this material is temperature-dependent. The model accounts directly for the influence of temperature on the effective elastic properties (both through the lattice constants and through the total porosity), and on the dominant dislocations and grain boundary relaxation processes. It is shown via compliance measurements that the strength of the dislocation relaxation (and by inference the grown-in dislocation density) increases dramatically with the brine porosity.Naturally occurring sea ice grown in the presence of a current offers the further complexity that the c-axes of the constituent hexagonal crystals tend to align themselves with the direction of the current. Because of the overwhelming ease of slip on the basal plane relative to other slip systems, the fabric thus produced has major influence on the mechanical properties. This effect of fabric has been incorporated in the model and verified with laboratory experiments on aligned sea ice specimens.Discussion centers on the physical basis of the model and it is shown that the model predictions compare favorably with the available experimental data.