An Integrated Method for Full-Field Stress Measurement via Coupled In-Situ Digital Image Correlation and Electron Backscatter Diffraction

Abstract A novel method is proposed to measure the stress field on the surface of polycrystalline samples by combining in-situ Digital Image Correlation (DIC) and Electron Backscatter Diffraction (EBSD). DIC provides full-field strain measurements in two dimensions, both at peak load (total strain, εt) and in the unloaded state (plastic strain, εp), during a fatigue test with a stress ratio of zero. The elastic strain field, obtained from the difference between εt and εp, can be used to estimate the stress field by applying a rotated stiffness matrix, in which the rotation matrices are derived from the crystallographic orientations identified by EBSD. The method is validated using a Crystal Plasticity Finite Element (CPFE) model under representative conditions at the fatigue crack tip. This approach enables accurate, full-field, and orientation-resolved stress analysis, offering a powerful tool for meso-scale mechanical characterisation.