Abstract
A hybrid moire -finite element (FE) analysis was used to determine the crack tip opening angle (CTOA) along a tunneling crack front in a single-edged notch, three-point bend (SENB) specimen. The specimen was machined from a ductile 2024-T351 aluminum plate of 8.1 mm thickness and was prefatigued to an initial crack length to width ratio of α_0/W ≈ 0.45. The specimen was then subjected to stable crack growth of Δα ≈ 0.5 to 5.5 mm, after which the specimen was post-fatigued to mark the final crack front and loaded to failure. A quarter segment of the SENB specimen was modeled with a truncated 3-D elastic-plastic finite element (FE) model. Measured surface displacements, which were obtained by moire analysis, and stable crack growth were prescribed on the FE model. CTOA was obtained from the computed crack opening displacement, approximately 1 mm behind, and normal to the crack front. The good agreement between the measured and computed surface CTOA indicated the accuracy of this procedure.
