Strain accuracy enhancement of stereo digital image correlation for object deformation with large rotations

We propose a full-field stereo digital image correlation (DIC) strain measurement method to overcome the poor accuracy while measuring the deformation under large rotations. Such a drawback comes from the failure to consider rotation movements of the deformed objects when calculating their strain values. To address this, we first used a DIC matching algorithm combined with a rotated subset and feature point detection to obtain displacement fields. By employing a singular value decomposition method, we can then calculate rotation matrices of the strain windows before and after deformations. Finally, to eliminate the strain errors caused by rotation, we introduced the rotation matrices into the classical pointwise least squares DIC strain calculation method. Both numerical simulations and experiments are performed, and the accuracy and effectiveness of the proposed method are confirmed by the experimental results.