MicroCT (microtomography) quantification of microstructure related to macroscopic behaviour Part 1 - Fatigue crack closure measured in situ in AA 2090 compact tension samples

Microcomputed tomography (microCT) quantified crack opening in situ in a small compact tension specimen (AA 2090 T8E41) as a function of 3D position and of applied load. The same specimen was observed twice at two crack lengths. Some crack face areas were dominated by large asperities, while others were relatively flat. Large openings followed the sides of large asperities, with small openings elsewhere. The crack path and pattern of openings are discussed in terms of the variation in mesotexture. Before and after the crack extension, the pattern of open (and closed) voxels did not appear to change, suggesting that contact at a point near the crack tip will continue at the same portion of the fatigue cycle after the tip has receded. Testing parameters and macroscopic closure measurements link the present microCT measurements to studies in the literature.