A Meshless Global DIC Approach

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.