Application of high-performance DIC for a comprehensive evaluation of biaxial fatigue crack growth experiments

Precise determination of the remaining service life of technical components requires sufficient knowledge of fatigue crack growth behaviour and the growth rate of defects. Cracks in real components often experience multiaxial far field stresses due to their complex geometry and composite loadings acting on it. Digital image correlation (DIC) is well established for crack length and displacement measurements, but it usually requires sample preparation with speckle paint and interferes with mechanical extensometers. To overcome these limitations, we use a novel 2D DIC system combining a graphics processing unit (GPU) with a CoaXPress 2.0 camera, acquiring up to 3 GB/s of image data. It enables real-time evaluation of both integral strain like an extensometer and full-field DIC on images selected automatically in real-time. This combination enables the use of one single sensor for strain-controlled testing and fatigue crack growth characterisation. The full-field displacement is compared to a finite-element model (FEM) simulating the actual crack contour measured by the DIC system. The results show that high-performance DIC has the potential to simultaneously simplify crack-growth experiments and provide comprehensive fracture mechanical information.