Measurement of mixed-mode stress intensity factors using digital image correlation method

Applications of the digital image correlation method (DIC) for the determination of the mixed-mode stress intensity factors (SIF) is investigated in this paper. Experiments were performed on an edge fatigue cracked aluminum specimen using a special loading device, which is an appropriate apparatus for experimental mixed-mode fracture analysis. The full-field displacements around the crack-tip region of the test sample were calculated using DIC. And then the SIF associated with unavoidable rigid-body displacement motion were calculated simultaneously from the experimental data. The effect of the rigid body motion on the measured displacements was then eliminated using the computed rigid body translation and rotation. A coarse-fine searching method was developed to determine the crack-tip location. For validation, the SIF thus determined is compared with theoretical results, confirming the effectiveness and accuracy of the proposed technique. Therefore it reveals that the DIC is a practical and effective tool for full-field deformation and SIF measurement.

► We calculate mix mode stress intensity factors.
► A coarse-fine technique for crack tip determination was provided.
► Rigid-body displacement motion was eliminated.