Isoclinic versus arbitrary rotated intermediate configuration for gradient plasticity applications

Every multiplicative decomposition of the deformation gradient tensor into elastic and plastic parts is related to a local unloading process, which determines a so-called plastic intermediate configuration. Two kinds of such configurations are commonly used, at least in metal plasticity. The first one is connected with some fixed directions and is known as isoclinic configuration. The second may be chosen to be arbitrarily rotated and is called here arbitrary rotated intermediate configuration. We call formulation of plasticity from the point of view of these configurations respectively the isoclinic intermediate configuration approach (IIC-approach) and the arbitrary rotated intermediate configuration approach (ARIC-approach). It is known that in classical (local) plasticity, the IIC- and the ARIC-approaches may be viewed as alternative but equivalent. Under the assumptions made in the present paper, we show that this is generally no longer true, whenever gradient effects are involved.