Creep of Polycrystalline Ice

This paper discusses the extension of creep models for polycrystalline ice to include the effects of a non-monotonic loading history. Attention is focussed on cyclic loading since it is of direct relevance to the field problem of ice sheets subjected to oscillatory loads. The modeling approach is based on the internal variable concept in which the change in the underlying microstructure is described by the evolution of structure variables. Significant amount of work has been done using the internal variable concept for the cyclic loading of metallic materials. This serves as a basis for the development of cyclic constitutive models for ice, and is discussed here in some detail. The current paucity of test data essential for theoretical model development and verification underlines the need for systematic experimental research in the non-monotonic loading of ice.