Elastic anisotropy and micro-damage processes in polycrystalline ice

Abstract

This paper discusses numerical predictions of a microstructural damage model for polycrystalline ice which is presented in a companion paper [1]. The results are relevant for ice deforming at the high end of the quasi-static domain of loading. First, the fracture mechanics-based model of damage is investigated by comparing model predictions of the stresses to form (nucleate) the first microcracks with test data. This is followed by a detailed simulation of loading under uniaxial compression using the damage model and an internal variable creep model, also summarized in the companion paper [1]. This simulation allows the prediction of the evolving damaged elastic properties, and delineates the relative contribution of creep and microcracking to the total deformation.

The importance of load history on the deformation response is then illustrated by studying the influence of load path in biaxial loading. In these simulations, the competition between the mechanisms of failure by shear faulting and axial splitting is discussed in terms of the development of compliance anisotropy in the damaged body. Finally, the critical crack density is used as a macroscopic failure criterion to predict compressive strengths in the ductile-to-brittle transitional domain of strain rates, and its validity in more general states of stress involving different failure modes is questioned.