Theoretical Framework for Modelling the Behaviour of Frictional Materials

A constitutive theory is proposed, which possesses the possibilities of modelling all the important features or the behaviour or frictional materials such as: influence of all three stress invariants, coupling between deviatoric and volumetric response, dilatancy, softening, and different behaviour in loading and unloading. The basic constitutive assumptions are relations between properly defined stress and strain rate invariants, from which the component equations are derived by means of a suitable reformulation. After the incremental stress-strain relations have been derived, they are augmented by consistent loading/unloading criteria. Emphasis is given to a fundamental discussion of the general properties of the theory proposed and it is shown to fulfil all the formal requirements (causality, determinism, admissibility, form-invariance, continuity) that a properly formulated constitutive theory must obey. Moreover, the theory contains a surprisingly large number of classical as well as nonclassical theories as special cases. In particular, it contains formulations ranging from nonassociated plasticity theory, associated plasticity theory, hypoelasticity to elasticfracturing theory