Dissipation-consistent modelling and classification of extended plasticity formulations

TL;DR

This paper introduces a unified classification framework for extended plasticity models, including micromorphic and strain gradient formulations, based on dissipation-consistent modelling to clarify flow relations and yield conditions.

Contribution

It provides a novel unified treatment of various extended plasticity models by representing strain gradient plasticity as Eringen-type micromorphic continua and classifying models as serial or parallel.

Findings

Models are classified as serial or parallel.

Rate-dependent models are analyzed with smooth dissipation potentials.

Non-smooth models face challenges in local stress admissibility.

Abstract

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.