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Theses

Ductile tearing of AA2198 aluminium-lithium sheets for aeronautic application

Abstract : The purpose of this thesis consists in understanding the influence of microstructure on plastic anisotropy and fracture toughness for two grade 2198 Al-Cu-Li alloys. The sheet thicknesses are 2~mm and 6~mm. Two heat treatment conditions (T351 and T851) were studied for each grade. Multiscale characterization techniques including optical micrography, transmission electron microscopy and X-ray computed tomography have been used to identify materials microstructure and damage micro-mechanisms. Plastic anisotropy and thickness effect on plasticity have been investigated via tensile tests on smooth flat and notched flat specimens showing an anisotropic plastic behaviour along different loading directions. Ductile tearing behaviour was examined using small sized Kahn specimens and large panels M(T) tests. Fracture toughness anisotropy was investigated on different loading configuration tests. Fractography via scanning electron microscopy (SEM) and synchrotron radiation computed tomography (SRCT) have clarified the intergranular and transgranular mechanisms of fracture with respect to grain structure and heat treatment. Void growth is limited in the crack propagation regions. Finally, the finite element simulation of ductile tearing is based on the local approach to fracture using cohesive zone model (CZM). The cohesive parameters were adjusted on small sized Kahn specimens. Fitted parameters were employed to predict the ductile tearing behaviour of M(T) tests. Simulation results show that the fitted cohesive parameters are more sensitive for M(T) tests than for Kahn tests. The thickness effect was assessed using node release technique by analysing variation of stress and strain along thickness direction.
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https://pastel.archives-ouvertes.fr/pastel-00657028
Contributor : Bibliothèque Mines Paristech <>
Submitted on : Friday, January 6, 2012 - 11:08:47 AM
Last modification on : Thursday, September 24, 2020 - 6:30:07 PM
Long-term archiving on: : Monday, November 19, 2012 - 12:35:11 PM

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  • HAL Id : pastel-00657028, version 1

Citation

Jianqiang Chen. Ductile tearing of AA2198 aluminium-lithium sheets for aeronautic application. Materials. École Nationale Supérieure des Mines de Paris, 2011. English. ⟨NNT : 2011ENMP0040⟩. ⟨pastel-00657028⟩

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