Étude du comportement et de la fatigue d'un acier inoxydable ferritique en environnement thermomécanique et vibratoire

Abstract : In the automotive industry, non-linearities such as vibration or friction coupled with the non-linear behavior of materials tend to create new fatigue problems for structures undergoing thermal-mechanical loadings. As combustion temperature increases while engine mass need to decrease, thick cast-iron is often replaced by thin stainless steel sheet to produce exhaust manifolds. This solution is more sensitive to engine vibrations and therefore presents a risk of damage by high temperature vibration fatigue, which need to be studied in the design process. The first objective is then to predict the mechanical behavior of the elastic-viscoplastic stainless steel AISI 441 under complex loading conditions. A large experimental database is obtained at 300°C for different loading frequencies and stress amplitudes to perfectly understand the different mechanisms controlling the response of steel sheets. Strains are monitored with a high speed camera which enables to rebuild strain-stress curves in order to study the inelastic behavior of the stainless steel for a wide range of stress rates. Standard constitutive models are proven to be unable to correctly describe the behavior of the material under a high frequency loading. Improvements are proposed to characterize more precisely the steel behavior. At the same time, an experimental protocol is developed to characterize the impact of an elasto-viscoplastic pre-stress on the modal basis of a structure. Then, a calculation method for Dang Van criteria based on modal projection is finally developed and detailed. This method enables to reduce the calculation time of the fatigue life-time of complex structures using its modal basis.
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Contributor : Agathe Forre <>
Submitted on : Monday, December 19, 2016 - 5:10:36 PM
Last modification on : Wednesday, July 3, 2019 - 11:48:06 AM
Long-term archiving on : Tuesday, March 21, 2017 - 12:13:19 AM

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  • HAL Id : tel-01419635, version 1

Citation

Agathe Forre. Étude du comportement et de la fatigue d'un acier inoxydable ferritique en environnement thermomécanique et vibratoire. Mécanique des structures [physics.class-ph]. ENSTA ParisTech, 2015. Français. ⟨tel-01419635⟩

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