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Étude expérimentale et modélisation du formage superplastiqued’un alliage d’aluminium Al7475

Abstract : Superplasticity is the ability of some materials to sustain very high value of strain (up to 2000%) under low stress and within a specific range of temperature and strain rate. Complex shape components combining low density and high strength can thus be elaborated by using this peculiar characteristic. Superplastic forming process consists in deforming a flange by applying a variable pressure until the flange takes the form of a die. A good knowledge of the pressure law to apply is therefore primordial in order to avoid damage and obtain homogeneous thickness distribution. Numerical simulations are generally used to predict the optimal forming conditions. But a precise description of the rheological response of the material (in terms of flow rule and damage evolution) under thermomechanical conditions representative of the process is necessary. The PhD work introduces several rheological models to describe the behavior of a 7xxx aluminum alloy during superplastic forming process. The work is divided into three parts: (i) characterization of rheological models, (ii) characterization of damage models and (iii) development of numerical simulations to predict the superplastic forming of typical shapes. Hot uniaxial tensile tests have been performed to characterize the rheological behavior of a 7475 alloy. Three models (i.e. Norton-Hoff, Johnson-Cook and Zener-Hollomon) have been identified but only the last one leads to a good prediction of the material response. A GTN damage model has also been identified. Observations by X-rays micro-tomography have allowed studying in more details the damage evolution during the deformation. From these results, different cases have been simulated in ABAQUS.
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  • HAL Id : tel-01141644, version 1


Jian Yang. Étude expérimentale et modélisation du formage superplastiqued’un alliage d’aluminium Al7475. Mécanique des matériaux [physics.class-ph]. Ecole nationale supérieure d'arts et métiers - ENSAM, 2014. Français. ⟨NNT : 2014ENAM0006⟩. ⟨tel-01141644⟩



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