Effect of the mesh size of the vector displacement field on the strain estimate in the digital image correlation method

Pyramidal adaptive meshing for Digital Image Correlation dealing with cracks

“…In experimental cases, defining which elements need to be divided is not straightforward. There are several choices, among them the maximum eigen strains [34,32,33] and the gray level residuals [28,21,24,26,31,34,27]. It is worth noting that the eigen strains are computed as the average over each element.…”

“…With the previous proposition, it is concluded that * is also length dependent. This proposition departs from the use of a unique strain threshold [31,32,33] when multiple refinement steps are to be performed. Both thresholds (i.e., * 1 and * ) introduced herein relate to the measurement uncertainties of the associated quantities (i.e., 1 and ).…”

“…Such h-refinement procedure has to be dealt with care since DIC analyses are inverse problems, namely, the finer the discretization, the higher the measurement uncertainty [18,30], yet the interpolation error is lower [28]. Heterogeneous h-refinement is appealing when dealing with localized phenomena such as strained bands [31] or cracks [32,33] to better capture high strain gradients [34]. As before, one critical aspect is related to the criterion for selecting elements to be refined.…”

“…As before, one critical aspect is related to the criterion for selecting elements to be refined. Several choices are possible, among them strains [32,33] and gray level residuals (GLR) [31,32,27].…”