Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 45: Topical Session (Symposium MM): Fundamentals of Fracture
MM 45.4: Vortrag
Mittwoch, 14. März 2018, 18:00–18:15, TC 006
Towards physically-based fatigue design in ductile polycrystalline metals — •Christian Robertson1 and Christophe Déprés2 — 1DEN-Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, Gif-sur-Yvette, France — 2Laboratoire SYMME Université de Savoie74940 Annecy-le-Vieux, France
Actual components withstand in-service conditions involving many aggravating factors, including: multi-axial loading, variable amplitude and mean stress. These factors and the inherent data scattering due the microstructural material heterogeneities are usually addressed by adopting important (if not overly conservative) safety margins. In other words, none of the standard fatigue design approaches are truly predictive, missing out cyclic plasticity mechanisms involved during crack propagation, in actual poly-crystalline metals.
The fatigue response of ductile poly-crystalline metals involves dislocation motion and multiplication, at the scale of individual grains (1-100 *m, typically). Two-dimensional dislocation dynamics (DD) studies adapted to crack propagation have been conducted earlier and were able to capture several fatigue lifetime controlling mechanisms. Our goal in this paper is to further investigate fatigue crack propagation using DD simulations, including 3D boundary conditions adapted to face-centred cubic grains, in presence of both short (stage-I) and long (stage-II) cracks. The results are analysed quantitatively, with a view to develop advanced fatigue design criteria and concepts, accounting for typical complex loading conditions and material microstructural heterogeneities.