Phase-field models for ductile fracture: a comparative study

Resumo

Fracture is a usual failure mode of engineering structures. Thus, the prediction and prevention of
cracking-induced failure is a crucial point in engineering projects. Many formulations have been proposed for
modeling this phenomenon. The Phase-Field (PF) theory has become popular because it couples Continuum
Damage Mechanics and Fracture Mechanics principles. Initially proposed for brittle fracture, the PF theory has
been extended for ductile materials. A possible strategy is introducing a yield surface degradation function that
depends on the PF variable. Besides this consideration, the stored energy must also be changed, including a plastic
work contribution. A different option is to couple the yield surface degradation function with a fracture toughness
depending on the accumulated plastic strain. In this case, the phase-field driving force remains defined only by
the elastic strain. From this context, this paper presents both PF models’ formulations applied to an elastoplastic
constitutive model and their implementation. These two approaches are compared. The material parameters are
also evaluated to identify how they influence the models’ behavior. Finally, numerical simulations via the Finite
Element Method are presented to highlight the ductile phase-field models’ main characteristics.