Digital image correlation using ring template and quadrilateral element for large rotation measurement

High accuracy measurement of the large rotation is a crucial issue in engineering. In this paper, the displacement hypothesis of quadrilateral element in finite element method (FEM) is chosen for digital image correlation (DIC) technique, and Newton–Raphson iterative method is selected to solve the partial differential equation to measure the displacement field. Because the ring template possesses rotation invariance and translation invariance, ring template matching technique is presented to estimate the integer pixel displacements of nodes which could make the initial value of the iterative method close to the real value. Simulated images are used to verify the performance of the improved DIC technique which shows that this method has a low request to the speckle pattern and the measurement range of the rotational angle is from 0° to 360° with high accuracy. Furthermore, the improved DIC technique is used to measure the large deflection deformation of the polyurethane specimen and the measured deformation is in accordance with the actual deformation of the specimen. All the results show that the improved DIC technique could be used to measure the large rotation and the application scope of DIC technique is extended.

► We use ring template matching technique for initial estimation of DIC which could cut decorrelation effect due to large rotation.
► The large rotational angle from 0° to 360° could be measured with a high accuracy.
► The developed technique is useful to measure the large deflection deformation, large amplitude vibration, torque and rotational speed.