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Apport des mesures de champs cinématiques à l'étude des micromécanismes d'endommagement en fatigue plastique d'un acier inoxydable duplex

Abstract : The aim of this work is firstly to develop an in-situ microscopy device to perform surface damage observations at the microstructural scale (images of 120 x 90 Μm2) on standard duplex stainless steel fatigue specimen during low-cycle fatigue tests, and secondly, to acquire digital images regularly during cycling to analyse damage thanks to kinematical fields calculated by digital image correlation (DIC) technique (CORRELILMT and CORRELIQ4 softwares). Surface observations allow to identify and to follow development and localisation of cyclic plastic strain, to identify microcrack initiation sites, and to follow propagation of these cracks at the surface. These observations combined with EBSD analysis enable to identify activated slip systems in each phase. The relief measurements by interferometric profiler allow to characterise the morphology of the slip markings appeared at the surface. The random surface texture necessary to DIC is obtained by a lightly electrochemically etching of the specimen. Fields measured highlight strain heterogeneities at grain scale, cumulated plastic strain levels and their dispersions in each phase. They allow also to detect the probable microcrack initiation sites, very before their observation. The study shows the complementarity of the various techniques used, in particular the interest of field measurements at the microstructural scale, towards the understanding of low-cycle fatigue damage in a two-phased material such as a duplex stainless steel (grain size is about 10 Μm).
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https://tel.archives-ouvertes.fr/tel-00254732
Contributor : Ahmed El Bartali <>
Submitted on : Wednesday, February 13, 2008 - 2:01:06 PM
Last modification on : Tuesday, November 24, 2020 - 2:18:04 PM
Long-term archiving on: : Friday, November 25, 2016 - 8:50:05 PM

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Ahmed El Bartali. Apport des mesures de champs cinématiques à l'étude des micromécanismes d'endommagement en fatigue plastique d'un acier inoxydable duplex. Mécanique [physics.med-ph]. Ecole Centrale de Lille, 2007. Français. ⟨tel-00254732⟩

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