Comment on the papers ‘Creep and recrystallization of large polycrystalline masses’ by Faria and co-authors

In a series of three papers, Faria and co-authors have presented the application of the theory of mixture with continuous diversity to the creep and recrystallization processes of large polycrystallinemasses. In this approach, amaterial point of the continuum is composed of a huge number of grains defined by their crystallographic orientation. The polycrystal is then seen as a continuousmixture of lattice orientations. All the balance equations are expressed to describe the response of the polycrystal and of a group of crystallites sharing the same lattice orientation (i.e. a species). To go further, Faria and co-authors have to make the hypothesis that the strain rate of every species is equal to the strain rate of the polycrystal, and is therefore independent of its lattice orientation. Furthermore, Faria and co-authors insist on the fact that this hypothesis is negligible and has no relation at all to any kind of Taylor-type constraint on the deformation of individual grains, arguing that in their theory of strain rate inhomogeneities on the grain level are smeared out because each species is composed of a very large number of crystals. In this comment, I show that the results obtained with a full-field model suggest that this hypothesis is not insignificant.