LAUSR

Abstract. Two-dimensional digital image correlation (2D-DIC) has the advantages of high computation efficiency and simple experimental setup compared to three-dimensional DIC (3D-DIC). However, 2D-DIC is sensitive to out-of-plane motion, which leads to rather poor strain results. Recently, optical extensometers realized by dual-reflector imaging have been proposed, which can self-compensate the strain errors introduced by out-of-plane motion of the specimen. We will extend strain measurement from an extensometer to full-field deformation measurement. To this end, first, two corresponding areas of interest (AOIs) are created based on the symmetrical axis of the reference image. Second, the displacement and strain fields of these AOIs are computed with a common 2D-DIC algorithm, respectively. Subsequently, high-accuracy deformation results are obtained by taking the average of the deformation of the corresponding calculation points in two AOIs. Two types of uniaxial tensile tests that correspond to uniform and nonuniform strain fields were conducted to validate the feasibility of the proposed self-compensation method. The first experiment indicates that the strain results obtained using the proposed method are in good agreement with those with strain gauges and that the proposed method can achieve higher strain accuracy than 3D-DIC with a small stereo-angle. The results of the second experiment are basically in agreement with those of the ANSYS numerical simulation, which demonstrates the feasibility of the proposed method for the measurement of nonuniform strain fields. Both of the experiments demonstrate that rigid out-of-plane motion will lead to a global strain field error for common 2D-DIC. With no external compensation device, the proposed self-compensation method has the potential in 2D-DIC for accurate strain measurement due to its high level of accuracy.