An integral regularization method was applied to the Gurson-Tvergaard-Needleman (GTN) damage model to address the plastic deformation localization at the crack tip. The parameters for the constitutive model were calibrated with an evolutionary algorithm. The model was applied to predict ductile fracture of a tensile specimen, allowing mesh convergence and geometry independence. Fatigue crack growth was predicted through a node release strategy, obtaining a very good approximation to the experimental results in the upper part of the Paris Regime. Mesh independence was verified for medium/high Δ K  levels, but near the threshold regime no mesh independence was obtained and da/dN was overestimated. The characteristic length for the non-local model was defined as the reverse plastic zone size, which indicates that this should be the fatigue process zone. Finally, at the accelerated regime, final fracture loci predictions agree with the experimental results, but mesh independence was barely achieved.

Fatigue results from the occurrence of several damage mechanisms and their interactions. The cyclic plastic strain and damage accumulation at the crack tip are widely pointed as the main agents behind FCG. In this work, the authors propose the prediction of FCG through a node release numerical model that offers several possibilities regarding the modelling of the mechanisms behind fatigue. A hybrid propagation method is presented where both cumulative plastic strain and porous damage represent parallel propagation criteria. Accordingly, the node is released once either a critical plastic strain or a critical porosity, at the crack tip, is reached. The Gurson-Tvergaard-Needleman (GTN) damage model is employed to predict porous damage evolution through the processes of nucleation and growth of microvoids. The model is validated through comparison with experimental data. Finally, the interactions between plastic strain, porous damage, crack closure and stress triaxiality are accessed.