A comparison between FEM predictions and DIC results of crack tip displacement field in CT specimens made of titanium

In the context of fatigue crack growth (FCG), the validation of FEM predictions with experimental results has been made in terms of crack closure and da/dN. The objective here is to compare the prediction of the displacement field, which is the primary output of FEM, with experimental results obtained with Digital Image Correlation (DIC). The qualitative comparison indicates that DIC and FEM results are very similar. The comparison of CTOD curves obtained behind the crack tip showed a good agreement between the DIC and numerical predictions obtained under plane strain conditions. This indicates the dominance of the interior regions over the surface displacements, although the small thickness of the specimen (1 mm). The more detailed analysis of the CTOD loops, through the values of plastic CTOD ranges, showed a significant difference between FEM predictions and DIC results. The robustness of the numerical model was checked considering a mesh sensibility analysis, as well as considering different sets of material parameters in the simulation.