(a) A uniaxial loading specimen showing the region of interest as a red rectangle. (b) Vickers indentation marks on the polished specimen viewed with the optical microscope. (c) Results of the EBSD scan showing grain geometry and orientation in relation to the same Vickers indentation marks as in (b).
Relative image sizes at several magnifications. The region of interest is imaged at high resolution using an array of high magnification images to cover the region outlined by the indentation marks.
(a) Contour plot of the strain field with overlaid grain boundaries. The reference and deformed images are a composite of 316 images at 31× magnification (ex situ). (b) A portion of the contour plot in (a) is magnified to show the strain localizations that can be resolved with this technique. Note the arrows indicating localization at a twin and a grain boundary. (c) Grain orientation map of the region shown in (b). (d) Contour plot of the strain field at low magnification (5×) of the same region shown in (a). Note that the subset size in (b) is much smaller than the one used in (d), which results in higher resolution fields with subgrain level accuracy.
Contour plot of the strain field around the tip of a fatigue crack with overlaid grain boundaries (a combination of 112 DIC results at 50× magnification). Only the upper half of the field is shown here to increase the detail that can be seen (note the upper three of five indentation marks). (b) A portion of the contour plot is magnified to show the strain localizations that can be resolved with this technique. Note the strain concentrations on two grain boundaries indicated by arrows. (c) Grain orientation map of the region shown in part (b).
DIC strain artifacts due to stitching error for a set of four images. No loading took place between the reference and deformed images. The specimen was simply removed and reinserted into the microscope. Strain artifacts [Figs. 3(c) and 3(d)] appear because the relative displacement between each corresponding reference and deformed image in the set is different [Figs. 3(a) and 3(b)].
Contour plots of strain fields at various global strain levels created by stitching 15 images together before correlating. Strain fields with global strains of (a) 0.23%, (b) 0.36%, (c) 1.08%, and (d) 3.04%. As global strain increases, strain artifacts due to stitching become less dominant. Stitching strains become negligible around 1% global strain.
Measurement resolution properties at several magnifications for a camera with a pixel size of .
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