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Digital Image Correlation is a non-contact, full-field technique that enables the measurement of the displacements on the surface of a specimen by tracking surface patterns. Hence, it allows for measurements of strains and kinematic quantities, such as velocities and accelerations. In addition, Digital Image Correlation has been used quite extensively to detect and measure cracks in specimens during fatigue tests or structural applications. In such a context, most of the existing methods require the preliminary calibration of a threshold value as a result of a user-dependent procedure. The threshold is then used to determine whether a crack is present or not on the basis of either strain or displacement measurements. This study presents a novel post-processing methodology for Digital Image Correlation measurements to detect crack paths, which does not depend on material properties or require preliminary calibration using secondary measurement systems. The methodology involves the analysis of the displacement field along virtual line gauges, aiming to identify a discontinuity in this displacement field using the Chow test. The method is validated using two sets of experiments, i.e., on pre-cracked SE(B) specimens subjected to static loading, and on a C(T) specimen under cyclic loading. The satisfactory comparison with well recognized sensor-based approaches highlights the robustness of the proposed method.
Leonetti et al. (Tue,) studied this question.