Balanced viscosity solutions to a rate-independent coupled elasto-plastic damage system

A rate-independent model coupling small-strain associative elasto-plasticity and damage is studied via a vanishing-viscosity analysis with respect to all the variables describing the system. This extends the analysis performed for the same system in [V. Crismale and G. Lazzaroni, Calc. Var. Partial Differential Equations, 55 (2016), 17], where a vanishing-viscosity regularization involving only the damage variable was set forth. In the present work, an additional approximation featuring vanishing plastic hardening is introduced in order to deal with the vanishing viscosity in the plastic variable. Different regimes are considered, leading to different notions of Balanced Viscosity solutions for the perfectly plastic damage system, and for its version with hardening.