Localization of deformation in polycrystalline ice

Since ice deforms mainly by dislocation glide on the basal planes, very strong incompatibilities exist between the grains of a polycrystal. Specially designed two-dimensional compression creep tests on different types of ice multicrystals embedded in a matrix of fine-grained isotropie ice allow to observe the strain heterogeneities which arise during the deformation of polycrystalline ice, and which are the consequence of inter-granular strain incompatibilities. The main features observed were bending and kink bands initiated at triple junctions or at geometric defects of the grain boundaries. These bands developed perpendicularly to the observed basal slip lines and provided additional degrees of freedom for the accommodation of inter-granular deformation. Mechanisms related to dislocations motion and dynamic recrystallization are proposed for the initiation and for possible development of the observed localization features.