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

Abstract

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 K_II and K_III 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.