Abstract
This work forms part of the research effort to investigate the transferability of CTOA from standard DWTT specimens to other geometries, notably pipes. The focus of this work is on the effect of ligament size and thickness of DWTT specimens under bending load on CTOA. The damage mechanics models used in this work, namely the modified Xue-Wierzbicki (XW) model and the Modified Mohr-Coulomb (MMC) model, utilize fracture criteria that depend on stress state, i.e., stress triaxiality and Lode angle. Both the XW model and the MMC model predict similar trends regarding the effect of ligament size and thickness on CTOA. For both the standard and large DWTT models with various thicknesses investigated in this research, steady-state crack growth was achieved at a small crack extension of about one specimen thickness. The CTOA values measured on the surface are larger than those measured in the interior, which is consistent with experimental observation. Increase of thickness has negligible effect on interior CTOA, but leads to higher surface CTOA. Increase of width (ligament) decreases CTOA slightly. However, further work is needed on the models because not all features are correctly predicted. In particular, the fracture mode is predicted by the models to show increasing slant fracture with increasing thickness, contrary to expectation. Also, the effect of ligament size on CTOA in tension-loaded specimens should be investigated to assess transferability to pipe in which the loading is tensile.
