Evaluation of stress intensity factors using meshless integrated digital image / volume correlation

A meshless approach is proposed for Integrated Digital Image Correlation (I-DIC) and Integrated Digital Volume Correlation (I-DVC) to measure stress intensity factors (SIFs), which is validated through synthetic experiments. Combined with double cleavage drilled compression (DCDC) experiments on gypsum and in-situ X-ray computed tomography, meshless I-DIC quantifies SIFs and their variations along the surface crack path, while meshless I-DVC resolves SIF distributions along internal crack fronts. SIFs are inferred directly from images, thereby eliminating error accumulation from displacement projection and avoiding meshing challenges near tortuous crack surfaces. In a virtual crack test, a comparative analysis of meshless I–DVC, a post-processing method and mesh-based I-DVC reveals errors of 0.7%, 2.0%, and 1.2% for the three approaches, respectively, highlighting the effectiveness of the proposed method. In DCDC uniaxial compression, I-DIC results indicate that the mode I SIF component dominated along the surface crack path, while the mode II SIF increased markedly as the crack propagated, consistent with mixed mode I-II propagation. I-DVC further revealed that the mode I SIF remained predominant along internal fronts, while the KII and KIII components in local areas gradually emerged as the crack propagated, evidencing opening accompanied by shear and tearing effects. The energy release rate profiles exhibited pronounced spatial non-uniformity and support an inside-out growth mechanism originating from internal flaws.