Plasticity

Plasticity describes the non-reversible deformation of a material in response to applied forces. The physical mechanisms that cause plastic, that is non-reversible, deformation can vary widely. Consistent with the involved nature of plasticity, this chapter exhibits well-known concepts (yield criteria) and classical models (gradient theories, Kröner decomposition). Next, a decomposition-free approach to the modelling of plastic materials is developed through the essential role of the entropy production as a constitutive function. This allows a general scheme where the hyperelastic regime, the hypoelastic regime, and the hysteretic regime occur depending on the free energy and the entropy production. Polymeric foams are also modelled as hysteretic materials.