Semi-automatic deflection measurement using digital image correlation

In this paper an easy-to-use approach using cubic spline interpolation is proposed for providing initial estimations for digital image correlation (DIC) grid point locations and rotations on objects with major deflection. One of the main problems in using DIC for deflection measurements is that direct correlation fails since image sample rotations can differ considerably across two images. The proposed method uses manually chosen reference points to create a spline that describes deflection. Curve geometries are then taken into account when calculating initial guesses for DIC grid points. When the expected rotation is known at any given point image samples can be rotated prior correlation and matches can be found. The validity and accuracy is demonstrated through a series of tests.