Abstract
The advent of small-scale testing procedures coupled with scanning electron microscopy (SEM) imaging allow for high-resolution digital image correlation (DIC) studies to examine strain localization at the grain size length scale. A systematic study was performed to determine how speckle patterning parameters (speckle density and shape) affect strain resolution of DIC using SEM imaging. Strain resolution increased with increased speckle density from 23 to 58 % area fraction. Patterns with less than 23 % area fraction exhibited significant signal noise, and a loss in strain resolution due to inadequate correlation. It was also observed that when the edges of square speckles were aligned with SEM rastering directions, the noise in the e yy data was double the noise in the e xx data. Rotating the speckle to eliminate edge alignment with the rastering direction significantly decreased the e yy strain noise. Competing optimization requirements for the correlation parameters were needed to minimize strain intensity noise or maximize spatial resolution. Application of the optimization techniques to high temperature in-situ studies of Ni-based superalloys will also be presented.
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Acknowledgements
Funding was provided by the Air Force Research Laboratory (AFRL) STW-21 program FA9550-09-1-0014. The authors would like to thank Aimee Price, Research Associate of the Institute for Materials Research at The Ohio State University for the assistance in producing the patterns used for this study.
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Carter, J.L.W., Uchic, M.D., Mills, M.J. (2015). Impact of Speckle Pattern Parameters on DIC Strain Resolution Calculated from In-situ SEM Experiments. In: Carroll, J., Daly, S. (eds) Fracture, Fatigue, Failure, and Damage Evolution, Volume 5. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-06977-7_16
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DOI: https://doi.org/10.1007/978-3-319-06977-7_16
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