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 three-point bend (SENB) specimen. The specimen was machined from a ductile 2024-T351 aluminum plate of 8.1 mm thickness and was pre-fatigued to an initial crack length to width ratio of a 0 /W≈0.45. The specimen was then subjected to stable crack growth of varying Δa=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 FE model. Measured surface displacements, which were obtained by moire analysis, and stable crack growth with increasing load were prescribed on the FE model. The 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 are indicative of the accuracy of the procedure.
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