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Caractérisation de l'endommagement dans les aciers Dual-Phase à l'aide de la tomographie aux rayons X

Abstract : As part of the current context of requiring ever more efficient grades of steels in terms of resistance to stress and to damage, the Dual-Phase steels (DP) present an acceptable strength/ductility compromise. It is nevertheless necessary to have a better understanding of the mechanisms leading to the fracture of such steels. Damage mechanisms were studied in this PhD using X-ray tomography. In-situ tensile tests were carried out on several grades of DP steel, a ferritic steel and a martensitic steel in order to characterize each step of ductile damage. Qualitative observations and quantitative data on the nucleation of damage, the void growth and the coalescence of cavities were collected during these tests. This quantitative data was then used for the development and/or the validation of damage models. A prediction of the kinetic of nucleation was proposed and the Huang’s correction of the void growth model of Rice and Tracey accounting for the triaxiality was experimentally validated. For the first time, the step of void coalescence leading to fracture of materials was quantitatively characterized in an industrial material and coalescence criteria were locally applied on couples of neighboring cavities present in the studied specimen. The use of analytical models enabled a better understanding of the properties influencing the studied damage phenomena. The effect of the kinematic part of the strain hardening on void nucleation and void growth was notably emphasized and validated by performing complex loading tests.
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  • HAL Id : tel-00738820, version 1

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Caroline Landron. Caractérisation de l'endommagement dans les aciers Dual-Phase à l'aide de la tomographie aux rayons X. Other. INSA de Lyon, 2011. English. ⟨NNT : 2011ISAL0147⟩. ⟨tel-00738820⟩

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