Mareau, Charles (2007) Micromechanical modeling of self-heating and microplasticity in steels under cyclic loading. PhD thesis Mécanique et Matériaux, Laboratoire de Physique et Mécanique des Matériaux, ENSAM 2007ENAM0037 p.216.
Abstract
The rupture in high cycle fatigue is one of the main reasons for failure of parts in service. For steels, fatigue damage is caused by microstructural mechanisms due to the motion of dislocations. The present work aims to understand the interactions between the microstucture and the intrinsic dissipation induced by dislocations motion since decreasing the dissipation seems to lead to an increase of the fatigue limit. The experimental determination of dissipation from temperature measurements requires a specific formulation of the heat equation that comes from assumptions about the heat sources and the measurement facilities. The experimental tool enables to build a scale transition model that describes the various interactions between the dissipative mechanisms and the microstructure. During cyclic loadings, the dissipation is assumed to be either the consequence of the curvature of dislocations segments (anelasticity) or due to the viscoplastic slip of dislocations (inelasticity). The frame of crystal plasticty is used to set up a physical description of the dissipative mechanisms and the scale transition model, that is developped to take the complexity of the constitutive law into account, enables to consider the heterogenous nature of steels. The parameters identification process is made with low cycle fatigue stress-strain curves and seems to give good results. Finally, the model is mainly used in order to foresee the influence of loading or microstructure parameters.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Berveiller, Marcel and Favier, Véronique |
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| Date: | 19 December 2007 |
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| Board of examiners: | Chrysochoos, André and Maugin, Gérard and Tabourot, Laurent and Galtier, André and Weber, Bastien and Weng, George |
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| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
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| Discipline: | Mécanique et Matériaux |
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| Collection (Fonds): | ENSAM |
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| Institution: | ENSAM |
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| Department: | Laboratoire de Physique et Mécanique des Matériaux |
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| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
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| Uncontrolled Keywords: | Microplasticité, Fatigue, échauffement, Anélasticité, Acier, Dissipation micromécanique, Transition d'échelle, Fatigue, Steel, Dissipation, Self-heating, Scale transition, Crystal plasticity, Microplasticity |
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