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Effet des hétérogénéités microstructurales sur le comportement en fatigue multiaxiale à grand nombre de cycles : application à l'usinage assisté laser

Abstract : The purpose of this work is to modelize the damage mechanisms in multiaxial high cycle fatigue (HCF). The role of microstructural heterogeneities, and in particular those introduced via the manufacturing process of Laser Assisted Machining (LAM), is given particular attention. Firstly, in order to take into account the dispersion observed in fatigue data, a critical plane approach and a two scale model are proposed. More precisely, a Weibull type probabilistic approach is introduced in order to take into account the role of the microstructural heterogeneities on the fatigue behaviour at the macroscopic scale. The second part of the study concerns the use of a fatigue model in which plasticity and damage are coupled at the mesoscopic scale in order to reflect the effect of damage accumulation observed in HCF. The predictions from the two different approaches have been compared to experimental results for complex loading conditions (e.g. out-of-phase tensile-torsional loads, biaxial tensile loads, asynchronous or variable amplitude loads). It is shown that very good agreement is achieved and that it is possible to associate the two modelling approaches to obtain a probabilistic damage law for which a direct application is the creation of P-S-N curves (i.e. Probabilistic-Stress-Life curves) for any type of loading condition. The final part of this work is a study of the interaction between the LAM manufacturing process and the fatigue resistance of metallic components (i.e. steel and titanium alloys) made via this process. The role of the surface integrity (i.e. the microstructure, hardening, residual stress, surface roughness, etc) on fatigue damage is particularly investigated.
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https://pastel.archives-ouvertes.fr/pastel-00004274
Contributor : Ecole Arts Et Métiers Paristech <>
Submitted on : Friday, December 5, 2008 - 8:00:00 AM
Last modification on : Wednesday, November 29, 2017 - 9:42:45 AM
Long-term archiving on: : Friday, September 10, 2010 - 12:46:12 PM

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Huyen Nguyen Thi Thu. Effet des hétérogénéités microstructurales sur le comportement en fatigue multiaxiale à grand nombre de cycles : application à l'usinage assisté laser. Sciences de l'ingénieur [physics]. Arts et Métiers ParisTech, 2008. Français. ⟨NNT : 2008ENAM0018⟩. ⟨pastel-00004274⟩

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