Abstract
The formulation of global Digital Image Correlation (DIC) is almost identical to standard (i.e. subset-based) DIC: indeed, in both cases the solution algorithm tries to minimize the error between the reference and test image by adjusting the shape-function-controlling parameters, but in the former, a modification of the parameters affects the displacement field globally, whereas in standard DIC the modification is local.
There are several ways to implement a global DIC program, but the approach most used relies on a Finite-Element-like mesh. This solution gives maximum flexibility with regard to description of the computational domain, but it makes it difficult to implement adaptive algorithms because a complete re-meshing infrastructure has to be employed. Considering that normally DIC codes are used to analyze relatively simple domains, this work propose to replace the standard FEA formulation with a mesh-less description of the displacement field; using Shepard’s approach, a partition of unity can easily be constructed, thus allowing for a simple and flexible description of the global displacement field.
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Notes
- 1.
Sometimes the sampling step is smaller than the side of the (rectangular) local area, thus part of the known terms (the intensities of pixels) are shared by adjacent sampling points. Obviously, no extra information content is added by this supersampling, which is equivalent to a low-pass filtering of the data.
- 2.
For example, C 0 continuity requires that the displacement along a segment connecting two nodes i and j shall depend only on a i and a j . While this condition is easily obtained, C 1 continuity cannot be obtained using u x and u y as the only controlling parameters and extra degrees of freedom have to be inserted in the formulation.
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© 2016 The Society for Experimental Mechanics, Inc.
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Baldi, A., Bertolino, F. (2016). A Meshless Global DIC Approach. In: Jin, H., Yoshida, S., Lamberti, L., Lin, MT. (eds) Advancement of Optical Methods in Experimental Mechanics, Volume 3. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-22446-6_22
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