Ben tahar, Mehdi (2005) Contribution a l'étude et la simulation du procédé l'hydroformage. PhD thesis Mécanique Numérique, ENSMP - CEMEF Centre de Mise en Forme des Matériaux, ENSMP.
Abstract
The hydroforming process consists in plastically deforming a work piece by the combined action of a pressurized liquid and a rigid die. The present work aims at contributing to the modelling of this process. This contribution concerns three items: Material characterisation, necking prediction and the development of specific numerical algorithms for this process.
- The experimental identification of hardening curves at large deformations is necessary in order to avoid inappropriate extrapolations during numerical simulation. To this end, a circular bulge test using a homogeneous analysis model has been developed. Very satisfactory results have been got thanks to the local measurement of sheet curvature radius.
- The prediction of necking during hydroforming operation is crucial for the process control. In this optic, the Modified Maximum Force Criterion has been deeply studied. We have demonstrated that the local shape of the yield surface is the most influencing factor on the model prediction. The strain path dependency of the FLC has been also approached and the usefulness of the definition of the FLC within the equivalent strain space has been underlined. Finally, we proposed a model including the strain rate sensitivity effect. The confrontation with experimental FLCs has shown an improving in the model prediction.
- The third aspect has dealt with numerical modelling. In one side, an implicit schema based on iteratively mesh updating and taking into account the domain derivatives has been tested. The results have shown the second order influence of domain derivatives and an improving of volume conservation. On the other side, it is well known that some ductile materials can present a certain deformation potential beyond the pick pressure (usually considered as the limiting point). For a correct simulation of such behaviour, we have developed several variants of the continuation method. Based on prediction-correction technique, these methods enable to go over the pick pressure which still insurmountable point for the standard pressure control method.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Massoni, Elisabeth |
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| Date: | September 2005 |
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| Board of examiners: | Batoz, Jean-Louis and Boudeau, Nathalie and Manach, Yves and Bel hadj salah, Hédi and Duroux, Patrick |
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| Ecole Doctorale: | ED 364 SCIENCES FONDAMENTALES ET APPLIQUEES |
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| Discipline: | Mécanique Numérique |
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| Collection (Fonds): | ENSMP |
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| Institution: | ENSMP |
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| Department: | ENSMP - CEMEF Centre de Mise en Forme des Matériaux |
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| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
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| Uncontrolled Keywords: | Hydroforming, Plastic anisotropy, Hardening law, Shear test, Bulging test, Necking, Flc, Mmfc, Strain rate sensitivity, Finite element method, Meshing remeshing, Arc length method, Numerical simulation, Hydroformage, Plasticité anisotrope, Loi d’écrouissage, Essai de cisaillement, Essai de gonflage, Striction, Clf, Cfmm, Sensibilité à la vitesse, Méthode élément fini, Maillage remaillage, Méthodes de longueur d’arc, Simulation numérique |
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