The resolved shear stress on the non-active slip systems in Taylor/Bishop-Hill models for fcc polycrystals

According to the Bishop-Hill rate-insensitive model for the plastic deformation of polycrystal, there are, in a grain of a given orientation, 6 or 8 potentially active {111} 〈110〉 slip systems with a resolved shear stress equal to the critical resolved shear stress. However, investigations demonstrate that for fcc materials with {111} 〈110〉 slip that the resolved shear stress on the slip systems which are not potentially active according to the rate-insensitive Taylor/Bishop-Hill model is zero. It is argued that this implies an effective ambiguity in the selection of slip systems even with rate sensitivity.