Study of systematic errors in strain fields obtained via DIC using heterogeneous deformation generated by plastic FEA

In this article, systematic errors that arise in the derivation of strain fields based on displacement fields obtained by digital image correlation (DIC) are analysed. Attention is paid to errors that arise from different implementations of the DIC technique. In particular, we investigate the influence of the shape function, the interpolation order and the subset size on the derived strains. In addition, we focus on errors that can be directly attributed to the derivation of the strain fields, e.g. the strain-window size and the strain-window interpolation order. The errors are estimated using numerically deformed images that were obtained by imposing finite element (FE) displacement fields on an undeformed image yielding plastic deformation of the specimen. This FE procedure simulates realistic experimental heterogeneous deformations at various load steps. It is shown that the errors on the strain fields can be substantially reduced if conscious choices in the abovementioned implementations are made.