20th European Conference on Fracture (ECF20) Anisotropic stress intensity factor ranges measurements with DIC

The effect of anisotropy on fatigue crack growth was studied using the stress intensity factor range in single crystal specimens. The material tested was the nickel based superalloy Haynes 230. Two different crystal orientations were cyclically loaded. Once a crack was observed, the entire loading and unloading process was optically recorded and the evolution of the displacements around the crack tip was obtained in terms of digital image correlation. Stress intensity factor ranges (���- �¬ and ���- �¬ �¬ ), together with T-stress, were extracted using a least-squares regression algorithm, based on the theoretical crack tip displacement in an anisotropc body. DIC displacements included crack closure effects, allowing the direct measurement of the effective stress intensity factor ranges. Crack propagation in the [001] crystal was only driven by �o�- �¬ , since the displacement field around the crack tip was symmetric and no �¬�- �¬ �¬ was measured On the other hand, the displacement field around crack tip in [111] crystal showed an asymmetric displacement profile, highlighting the presence of Mode II sliding. As expected, ���- �¬ �¬ measured by regression was found to be higher than ���- �¬ : this result was due to the crack angle, which was 55°. © 2014 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Norwegian University of Science and Technology (NTNU), Department of Structural Engineering.