DEVELOPMENT OF FABRIC IN ICE

A numerical model for the deformation and rotation of crystals in a polycrystalline ice mass produces crystal-orientation fabrics like those observed in glaciers. Major features of the model are that the stress on each crystal equals the bulk stress and that each crystal deforms by pure shear in a reference frame that rotates with the polycrystalline aggregate. The single-maximum fabric in ice deforming under simple shear is correctly simulated if it is assumed that recrystallizing crystals are seeded by crystals that are already present in one of the optimum directions, rather than forming entirely new crystals. The strain rate of the aggregate reaches a minimum at about 10% bulk strain, later than observed in the laboratory, probably because effects dominating the initial stages of deformation in laboratory experiments are not included in the model. The various crystal-orientation fabrics exhibit enhancement factors that agree with those measured in the laboratory.