  A unified classification framework for models of extended plasticity is
presented. The models include well known micromorphic and strain gradient
plasticity formulations. A unified treatment is possible due to the
representation of strain gradient plasticity as an Eringen-type micromorphic
continua. The classification is based on the form of the energetic and
dissipative model structures and exploits the framework of
dissipation-consistent modelling to elucidate the flow relation and yield
condition. Models are identified as either serial or parallel. This designation
is also applicable to familiar models of classical plasticity. Particular
attention is paid to the rate-dependent problem arising from the choice of a
smooth dissipation potential. The inability to locally determine the region of
admissible stresses for the non-smooth (rate-independent) parallel models of
plasticity is made clear.
