Figure 4.

FCG analysis of AA2024-T3 following the conventional ASTM methodology (a, blue) and DIC-based (a, black) with the interaction integral, both smoothed via a walking mean with seven data points window size. Both curves are close together, however, the conventional method only yields integral results, i.e. a − N and da/dN − ΔK. In contrast, we can now reveal local effects by high resolution DIC. (b) The local displacement field around the crack at low ΔK, with a mostly straight crack path and, (c) a branched crack path at higher ΔK resulting in non-symmetric displacements in front of the crack tip.