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Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 34: Topical Session: Fundamentals of Fracture - Fracture at the Atomistic Scale

MM 34.2: Talk

Wednesday, March 13, 2013, 12:00–12:15, H4

hydrogen enhanced dislocation emission at a crack tip — •yu wang1,2, damien connétable2, and döme tanguy11Laboratoire de Physique de la Matière Condensée et Nanostructures, Université Claude Bernard Lyon 1, 43 Boulevard du 11 Novembre 1918, F 69622 Villeurbanne, France — 2CIRIMAT, CNRS-UPS-INPT, ENSIACET 4 allée Emile Monso, BP 44362, F 31030 Toulouse, France

The influence of hydrogen on plasticity is an essential component of the modelling of H induced damage in structural metallic alloys. In this work, we study an idealized configuration where an atomistically sharp crack is loaded in mixed mode until a straight dislocation is emitted directly at the tip. It is shown, by Molecular Statics calculations using empirical EAM potentials, that the model proposed by Rice, which relates the critical stress intensity factor for emission (Ke) to the unstable staking fault energy (γus), is exact for dislocations moving along the crack plane (modes II or III dominate mode I), provided the influence of the mode I is taken into account in the γus calculation. The interest of combining Molecular Statics with the Rice model is that γus can be calculated on a system simple enough to be handled by ab initio methods. When dealing with hydrogen, on the contrary, there is no a priori knowledge how to introduce the H induced relaxations in the γus calculation, still preserving the relation between by γus and ke established by Rice. Therefore, Molecular Statics calculations with an empirical EAM potential for Al-H and Ni-H, on a large simulation box containing a crack, γus calculations with EAM potentials and ab initio calculations should be performed in parallel.

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