On sire effects in torsion of multi- and polycrystalline specimens

Simulations of torsion of copper single, multi- and polycrystals are presented. The stress is laid on an accurate description of intragranular behaviour, which requires the use of parallel computing. If the wire contains up to 1000 grains, the deformation is shown to localize within some weak sections of the specimen. A lower bound of a critical grain number for a multi- to polycrystal plasticity transition is therefore established