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Détermination des paramètres non linéaires constitutifs de lois de comportement viscoélastique par mesures de champ dans des écoulements complexes

Abstract : Today "molecular-based" constitutive equations for polymer melts are able to link molecular structure to macroscopic response in rheometric flows. However, these models may fail in the case of strong, complex flows. In this thesis, we presented experimental results that allowed us to identify the nonlinear parameters of some viscoelastic constitutive equations for polymer melts using field measurements such as laser Doppler velocimetry (LDV) and Flow Induced Birefringence (FIB). This method was used for a polystyrene (PS) and a low density polethylene (LDPE). For both materials, stress and velocity field measurements were performed in a convergent flow geometry (for PS) and a flow contraction (for LDPE). A method for assessing and identifying a viscoelastic constitutive law (Marrucci and Ianniruberto for PS, and a "Pom-Pom"-like model for LDPE) were then developed. Moreover, for LDPE, the influence of temperature and flow rate on the size of a secondary flow recirculation (vortex) was investigated. The size of these latter depends on the relative importance of rheological properties in shear and elongation of the material.
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Submitted on : Thursday, February 17, 2011 - 8:55:30 AM
Last modification on : Thursday, September 24, 2020 - 5:22:54 PM
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  • HAL Id : pastel-00566767, version 1

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Ghalia Boukellal. Détermination des paramètres non linéaires constitutifs de lois de comportement viscoélastique par mesures de champ dans des écoulements complexes. Matériaux. École Nationale Supérieure des Mines de Paris, 2010. Français. ⟨NNT : 2010ENMP0044⟩. ⟨pastel-00566767⟩

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