ABSTRACT This contribution deals with a method based on DIC (digital image correlation) analyses that allows the measuring range to be extended to smaller deformations by a special evaluation algorithm. Therein, the detected displacements (DIC raw data) are approximated by B‐splines with optimized smoothing. In order to assess the precision and accuracy of the method, it was applied and analyzed in a four‐point bending test with an aluminum beam with small occurring deformations (in the elastic strain range of the metal). The specimen strain in longitudinal direction between the load application sections was analyzed using 3D DIC and strain gage measurements. The results of the approximation‐based method show good agreement with strains obtained by strain gage data used as a reference measurement method. Therefore, good results regarding precision and accuracy of the presented strain determination method are obtained. In addition, an application example for the method—in this case extended to applications with circular boundaries—is presented. It demonstrates the deformation analysis of a borehole environment on a loaded plastic specimen on the basis of 2D DIC data, which can potentially be used in the context of residual stress analyses. The strain fields obtained in this way also exhibit a high degree of precision.
Lehmann et al. (2026) studied this question.