LATTICE ROTATION IN POLYCRYSTALLINE AGGREGATES AND SINGLE-CRYSTALS WITH ONE SLIP SYSTEM - A NUMERICAL AND EXPERIMENTAL APPROACH

In this study, lattice rotations in polycrystals and single crystals w ith one slip system have been analysed for pure shear and simple shear by re-visiting previously published data and by conducting new numeri cal models that are compared with results from experiments oil polycry stalline ice. The numerical models are based on the finite-difference method and on the assumption that dislocation glide on one slip system is the dominant crystalline deformation mechanism and is controlled b y the critical resolved shear stress law. Such a deformation scheme co rresponds to the operation of glide on (0001) in polycrystalline ice u sed in the physical deformation experiments. The results show that lat tice rotation is primarily controlled by the bulk deformation kinemati cs in both the polycrystalline aggregates and the single crystals. In the single crystals the lattice rotation is entirely consistent with t he vorticity of the bulk deformation kinematics, whereas in the polycr ystalline aggregates extensive grain interactions significantly modify the local lattice rotations and may even lead to the lattice planes o f individual grains rotating in an opposite sense to that of the bulk deformation. These results can reasonably explain the development of c rystallographic preferred orientations widely reported in the literatu re. (C) 1997 Elsevier Science Ltd.