Influence of closure on the 3D propagation of fatigue cracks in a nodular cast iron investigated by X-ray tomography and 3D Volume Correlation

Nathalie Limodin (1) , Julien Réthoré (2) , Jean-Yves Buffiere (1) , François Hild (3) , Stéphane Roux (3) , Wolfgang Ludwig (1) , Johann Rannou (2) , Anthony Gravouil (2)

1 MATEIS - Matériaux, ingénierie et science [Villeurbanne]
2 LaMCoS - Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne]
3 LMT - Laboratoire de Mécanique et Technologie

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 of a crack with crack closure in the COD maps or with a local value of the measured SIF range. It is shown that a non uniform closure process along the crack front induces an asymmetric arrest/growth of the crack.

Mots clés: Synchrotron X-ray microtomography; 3D Digital Image Correlation; Crack propagation; Stress Intensity Factors; Nodular graphite cast iron

Domaines: Mécanique des matériaux [physics.class-ph]; Mécanique des matériaux [physics.class-ph]

Nathalie Limodin, Julien Réthoré, Jean-Yves Buffiere, François Hild, Stéphane Roux, et al.. Influence of closure on the 3D propagation of fatigue cracks in a nodular cast iron investigated by X-ray tomography and 3D Volume Correlation. Acta Materialia, 2010, 58 (8), pp.2957-2967. ⟨hal-00453971v1⟩