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

We propose a full-field stereo digital image correlation (DIC) strain measurement method in order to overcome the poor accuracy while measuring the deformation under large rotations. Such drawback comes from the missing of considering rotation movements of the deformed objects when calculating their strain values. To address that, we first used a DIC matching algorithm combined with rotated subset and feature point detection to obtain displacement fields. By employing a singular value decomposition (SVD) method, we then can calculate rotation matrices of the strain windows before and after deformations. Finally, in order to eliminate the strain errors caused by rotation, we introduced the rotation matrices into the classical pointwise least square (PLS) 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.