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2016 | OriginalPaper | Chapter

22. A Meshless Global DIC Approach

Authors : Antonio Baldi, Filippo Bertolino

Published in: Advancement of Optical Methods in Experimental Mechanics, Volume 3

Publisher: Springer International Publishing

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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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previous chapter Comparison of Subset-Based Local and Finite Element-Based Global Digital Image Correlation

next chapter Out-of-Plane Motion Evaluation and Correction in 2D DIC

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.

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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Title: A Meshless Global DIC Approach
Authors: Antonio Baldi
Filippo Bertolino
Publisher: Springer International Publishing
Book: Advancement of Optical Methods in Experimental Mechanics, Volume 3
Print ISBN: 978-3-319-22445-9

Electronic ISBN: 978-3-319-22446-6

Copyright Year: 2016
DOI: https://doi.org/10.1007/978-3-319-22446-6_22

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