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Étude de l'endommagement par la découpe des aciers dual phase pour application automobile

Abstract : In order to optimize the metallurgical quality of future dual phase steels, the present study aims at a better understanding of the formation of the cut edge damage induced by shearing. Observations and characterizations revealed the existence of a highly deformed area in the vicinity of the cut edges. This region of 200 µm is defined as the cutting affected zone. In addition to deformation, its microstructure presents voids, initiated at ferrite-martensite boundaries. The formation of this zone during the cutting process was studied through two complementary approaches: first, the use of an especially designed testing device that allows precise interruption of the cutting process, then, the simulation of the process by finite elements methods. The damage and the fracture of the sheets appeared to be controlled by the voids formation at the phases boundaries and thus by the stress triaxiality ratio. The study of the cut edge behaviour under loading showed the rapid initiation of small cracks in the cutting affected zone. The direct impact of these cracks on the sheets ductility was also highlighted. Finally, two heat treatments that limit the ductility loss induced by cutting were proposed: one by the formation of a third phase during cooling and the other by offering better mechanical properties around phases boundaries.
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https://pastel.archives-ouvertes.fr/tel-00260080
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Submitted on : Monday, March 3, 2008 - 11:05:32 AM
Last modification on : Tuesday, October 20, 2020 - 11:24:36 AM
Long-term archiving on: : Thursday, May 20, 2010 - 8:29:03 PM

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  • HAL Id : tel-00260080, version 1

Citation

Alexandre Dalloz. Étude de l'endommagement par la découpe des aciers dual phase pour application automobile. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2007. Français. ⟨NNT : 2007ENMP1502⟩. ⟨tel-00260080⟩

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