A modeling approach for the complete ductile-brittle transition region: cohesive zone in combination with a non-local Gurson-model

The present study deals with the simulation of crack propagation in the ductile-brittle transition region on the macro-scale. In contrast to most studies in the literature, not only the ductile softening by void growth and coalescence is incorporated but also the particular material degradation by cleavage. A non-local Gurson-type model is employed together with a cohesive zone to simulate both failure mechanisms simultaneously. This consistent formulation of a boundary value problem allows arbitrary high mesh resolutions. The results show that the model captures qualitative effects of corresponding experiments such as the cleavage initiation in front of a stretch zone, the formation of secondary cracks and possible crack arrest. The influence of the temperature on the predicted toughness is reproduced in the whole ductile-brittle transition region without introducing temperature-dependent fit parameters. A comparison with experimental data shows that the shift of the ductile-brittle transition temperature associated with a lower crack-tip constraint can be predicted quantitatively.