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Propagation robuste de défauts en 3D

Abstract : In order to ensure the control of its nuclear power plants, EDF must guarantee that they function effectively over the long term. For this purpose, it is necessary to have efficient tools tomodel and simulate crack propagation in structures. In this PhD work, we are interested in the propagation of cracks with the X-FEM method which allows using the same mesh as for a structure without default. We target especially the reconstruction of thelevel sets that characterize the position of the crack after propagation. We have proposed a fast marching method approach based on the propagation of distance information from the crack surface to the whole structure to make this step more robust in the X-FEM propagation process. It is applicable to all types of meshes, linear or quadratic. The calculation of information characteristic of thecrack status such as the energy release rate and the stress intensity factors must be accurate enough to obtain the direction and advance of the crack front ateach propagation step. For this purpose, we proposed to study a domain integral method, for which several difficulties related to the representation of the crackin a three-dimensional space are identified. Several improvements are proposed to make the calculations more accurate and more robust. In the case of curved cracks front, we have identified the limitations of using asymptotic fields obtained under the plane deformation hypothesis as auxiliary fields of an interaction integral method and we have proposed new auxiliary displacement fields that take into account the curvature of the crack front. All these methods are developed and validated with EDF software code_aster.
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Matthieu Le Cren. Propagation robuste de défauts en 3D. Mécanique des solides [physics.class-ph]. École centrale de Nantes, 2018. Français. ⟨NNT : 2018ECDN0028⟩. ⟨tel-01952979⟩

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