In-plane displacements measurement by gradient-based digital image correlation

The basic assumption of gradient-based DIC method is the rigid body translation of the interrogated subset. However, this is in contradiction to the real circumstances where displacement gradients exist. In this paper the theoretical error analysis shows that the assumption of subset rigid body translation in gradient-based DIC and the linear approximation of the deformation mapping in N-R method yield identical subset center displacements. Then four real experiments are designed to explore the feasibility and sensitivity of this algorithm. The experiment of uniform uniaxial tension test of aluminum specimen is also investigated as a state when strains exist. The results show that the experimental data of the two algorithms are in good agreement, but the proposed algorithm is much faster than N-R method.