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Theses Year : 1988

Modélisation numérique du formage superplastique de tôles

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1
Michel Bellet

Abstract

The application of the superplasticity of metals has become an industrial reality in the aerospace industry since 1970. This property of large stable plastic deformation allows the thermoforming of structural parts made of thin sheets of titanium and aluminium alloys. The introduction and chapter I are a presentation of the general characteristics of superplasticity and of the forming process using fluid pressure. A better control of this process, especially regarding pressure cycles and final thickness profile, is conditionned by its numerical modeling. The author presents a mechanical model based on a membrane hypothesis. In chapter II, the equations are written in curvilinear coordinates for an elastic-viscoplastic or purely viscoplastic material, with isotropic strain hardening. The numerical resolution method is the finite element method. Its presentation, in the frame of membrane approximation, is in chapter III, in which the different possibilities for the integration of the behaviour law are discussed. Firstly, using and existing incremental displacement formulation, the author takes advantage of the direct relation between stress and viscoplastic strain rate to propose an implicit scheme in which elasticity is neglected. Secondly, the elastic-viscoplastic model is treated with an implicit velocity formulation, in which the unknown variable is the velocity field of the unknown current configuration and the behaviour equations remain written in terme of velocity. This new scheme gives a better precision than the displacement formulation. Chapter IV describes experimental simulation with plastine, resulting in the validation of the model. In chapter V, the application of the model to industrial forming operations is presented. An interesting characteristic of the computation code is an automatic numerical regulation of forming pressure which ensures the faisability of the forming in a minimum time.
Caractérisation générale de la superplasticité et du procédé de mise en forme des tôles par pression gazeuse. Présentation d'une modélisation numérique permettant une meilleure maîtrise de ce procédé de fabrication notamment utilisé dans l'industrie aéronautique pour le formage de pièces de structures en tôles d'alliages de titane ou d'aluminium.
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Dates and versions

pastel-00001392 , version 1 (10-03-2006)

Identifiers

  • HAL Id : pastel-00001392 , version 1

Cite

Michel Bellet. Modélisation numérique du formage superplastique de tôles. Sciences de l'ingénieur [physics]. École Nationale Supérieure des Mines de Paris, 1988. Français. ⟨NNT : ⟩. ⟨pastel-00001392⟩
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