title: Location, location &size: defects close to surfaces dominate fatigue crack initiation.
abstract: Metallic cast components inevitably contain defects such as shrinkage cavities which are inherent to the solidification process. Those defects are known to significantly alter the fatigue life of components. Yet very little is known, quantitatively, on the dangerosity of internal casting defects compared to surface ones. In this study, fatigue specimens containing controlled internal defects (shrinkage pores) are used to foster internal cracking. In situ fatigue tests monitored by X ray synchrotron tomography revealed that the internal nucleation and propagation of cracks was systematically overran by surface cracking initiated at castings defects up to ten times smaller than the internal ones. These findings indicate that the presence of internal defects in cast components can be tolerated to a larger extent than is allowed by nowadays standards.
authors.affiliation: Université de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, Villeurbanne Cedex, 69621, France.
authors.forename: Itziar
authors.initials: I
authors.lastname: Serrano-Munoz
authors.affiliation: Université de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, Villeurbanne Cedex, 69621, France.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Buffiere
authors.affiliation: Paul Scherrer Institute, CH-5235 Villigen-PSI, Switzerland.
authors.forename: Rajmund
authors.initials: R
authors.lastname: Mokso
authors.affiliation: Université de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, Villeurbanne Cedex, 69621, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Verdu
authors.affiliation: Institut Pprime, CNRS, ISAE-ENSMA, Université de Poitiers, Département Physique et Mécanique des Matériaux, Téléport 2, 1 Avenue Clément Ader, BP 40109, F-86961 Futuroscope Chasseneuil Cedex, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Nadot