A full three dimensional study of a fatigue crack in cast iron is presented. This analysis involves combining various tools, namely, Synchrotron X-ray microtomography Preprint submitted to Elsevier 4 October 2009of an in situ experiment, image acquisition and treatment, 3D volume correlation to measure 3D displacement fields, extraction of the crack geometry, extended digital image correlation to account for the crack displacement discontinuity, crack modeling in an elastic material exploiting the actual crack geometry, and finally estimation of stress intensity factors. All these different tasks are based on specific multiscale approaches.

Synchrotron X-ray tomography was performed during in-situ fatigue crack propagation in two small size specimens made of nodular graphite cast iron. While direct image analysis allows to retrieve the successive positions of the crack front, and to detect local crack retardation, volume correlation enables for the measurement of displacement fields in the bulk of the specimen. The Stress Intensity Factors (SIF) which are extracted from the measured displacement fields and the corresponding local crack growth rate all along the front are in good agreement with published results. In particular, it is possible to link the non propagation