Study of the tensile anisotropy of extruded ODS steel tubes using notched rings

Thibaud Jaumier (1) , Sébastien Vincent (2) , Ludovic Vincent (1) , Rodrigue Desmorat (3)

1 SRMA - Service des Recherches Métallurgiques Appliquées
2 STCP - Service de Technologie des Composants et des Procédés
3 LMT - Laboratoire de Mécanique et Technologie

Oxide dispersion strengthened (ODS) steels are suitable candidates for cladding applications in sodium cooled fast nuclear reactors. Obtained by means of cold rolling, ODS steel tubes can exhibit microstructural anisotropies, which translate into different mechanical properties in the hoop and axis directions. Assessing these properties and potential anisotropies is necessary should these materials be used. To this end, tensile tests are performed in the temperature range 400-750DC on two specimen geometries tiles for the axial properties and notched rings for the hoop properties. Simple tooling is used for the latter, consisting of two half mandrels to apply tension to the ring with the two symmetrical gauge sections set at the edges of the mandrels. Tests were not performed with any lubricant even at the higher end of the temperature range, resulting in potential undesirable effects of friction. The coefficient of friction, temperature dependent, was not evaluated by direct means. Instead, 2D digital image correlation (DIC) was used to evaluate the strain evolution in the gauge section. 3D finite-element simulations were performed with material parameters identified on the results of tension tests performed on tile specimens manufactured with an isotropic 9%Cr ODS steel tube. Comparison between experimental and numerical strain fields on the surface of the ring allows the extrapolation of the coefficient of friction and the inverse identification of the stress-strain mechanical behavior of the material in the range 400-750DC. Using the same methodology on an anisotropic 14%Cr ODS steel tube, the apparent anisotropy introduced by the specimen geometry can be adjusted and the relevant data be interpreted for the determination of the material-dependent anisotropy between the axial and hoop directions.Better assessment of the hoop properties using these notched rings, in particular the strain distribution in the width of the gauge section, can be further used with creep tests performed in similar loading conditions.

Mots clés: ODS; tube; anisotropy; ring

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

Thibaud Jaumier, Sébastien Vincent, Ludovic Vincent, Rodrigue Desmorat. Study of the tensile anisotropy of extruded ODS steel tubes using notched rings. EMMC16 - 16th European Mechanics of Materials Conference, Mar 2018, Nantes, France. ⟨cea-02339071⟩