A nonlocal triaxiality-dependent ductile damage model for finite strain plasticity

In this contribution a nonlocal damage-plasticity framework is developed which allows to describe the evolution of ductile damage in a continuum sense. Focus is on two main aspects of the ductile damage model, which constitute an improvement of recently developed theories. First, the degradation of both the elastic and plastic response is accounted for, using the concept of effective stress and strain equivalence between the homogenised and the hyperelastoplastic matrix material. Second, the role of the stress triaxiality in triggering ductile failure is taken into account by using a triaxiality-dependent local damage-driving variable, whose nonlocal counterpart acts as a localisation limiter. The resulting coupled problem, i.e., equilibrium and nonlocal averaging, is implemented in an implicit, fully coupled form, for which consistent tangent operators are derived. Details of the numerical implementation and remeshing issues are given. To illustrate the response of the model, simulations of tensile tests on notched and unnotched bars are compared with the results of previous models and with published experimental data.