Étude de la tenue en fatigue d'un acier inoxydable pour l'aéronautique en milieu marin corrosif

Abstract : This study addresses the effects of corrosion on the high cycle fatigue (HCF)strength of a martensitic stainless steel used in aeronautic applications. First, the geometry of corrosion pits on the fatigue strength in air at 10^7 cycles were studied with four different pit sizes. A new non-local fatigue criterion was proposed to simulate real shapes of pits as identified by X-ray microtomography. Corrosion fatigue synergy phenomena was studied by HCF tests (between 10^5 and 10^7 cycles) in a 0.1 M NaCl aqueous solution (pH = 6) with two load ratios (R = -1 and 0.1). Next, the electrochemical behavior of the passive film was investigated during in situ corrosion fatigue tests by free potential measurements and electrochemical impedance spectroscopy (EIS). Based on fractography analysis and electrochemical test results, corrosion fatigue crack initiation mechanisms were investigated. A scenario of fatigue crack initiation was proposed based on physical evidence. This scenario implied combined processes of local passive film rupture (induced by the cyclic loading), stress-assisted corrosion and enhanced pitting development. Local passive film ruptures were the main cause of the corrosion fatigue crack initiation. Finally, a analytical model for corrosion fatigue crack initiation was proposed based.
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Mohamed El May. Étude de la tenue en fatigue d'un acier inoxydable pour l'aéronautique en milieu marin corrosif. Autre. Ecole nationale supérieure d'arts et métiers - ENSAM, 2013. Français. ⟨NNT : 2013ENAM0012⟩. ⟨pastel-00917240⟩

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