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Etude des phénomènes de fatigue sur les alliages d'aluminium brasés de faibles épaisseurs pour les échangeurs thermiques automobiles

Abstract : Nowadays, most of the automotive heat exchangers are made of brazed aluminium sheets. Due to economic and environmental issues, the thickness of heat exchanger components have been reduced. Concomitantly, the stress undergone by the heat exchanger increased which raised the risk of fatigue failure, and particularly on tube for radiators. In this work, a detailed characterization of the cyclic damage mechanisms in car heat exchangers has been carried out. The standard material used to make radiator is a very thin (plu petit que 0.27mm) aluminium sheet composed by 3 layers (4045 /3916/ 4045). To assess the effect of the structure of this “sandwich” on the damage mechanisms, materials composed of a single layer (3916) and composed of 4 layers (4045/3003/3916/4045) have also been studied. All materials have been brazed in similar industrial conditions in order to obtain representative metallurgical and surface conditions. Fatigue tests at constant stress amplitude have been performed at room temperature, -30°C and 120°C to i) characterize the sandwich structure effect on the cyclic resistance of the studied materials and ii) to study the effect of temperature on the fatigue damage mechanism.Crack initiation and propagation have been observed by 2D and 3D monitoring techniques. These techniques, in addition to a detailed microstructure characterization of the materials, allowed to clarify the damage mechanisms leading to fracture in fatigue of these thin sheets and, in particular, to point out the key role of the residual clad (left by the 4XXX melting) on the damage mechanisms.
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  • HAL Id : tel-02001207, version 1

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Josselin Paturaud. Etude des phénomènes de fatigue sur les alliages d'aluminium brasés de faibles épaisseurs pour les échangeurs thermiques automobiles. Matériaux. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSEI011⟩. ⟨tel-02001207⟩

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