Stick-slip flow of high density polyethylene in a transparent slit die investigated by laser Doppler velocimetry
| Autor: | Bruno Vergnes, Yves Demay, Laurent Robert |
|---|---|
| Přispěvatelé: | Institut Non Linéaire de Nice Sophia-Antipolis (INLN), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), Centre de Mise en Forme des Matériaux (CEMEF), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS) |
| Rok vydání: | 2004 |
| Předmět: |
02 engineering and technology
Slip (materials science) 01 natural sciences Instability Physics::Geophysics High density polyethylene Physics::Fluid Dynamics Optics 0103 physical sciences General Materials Science Wall slip Plug flow 010304 chemical physics Extrusion Chemistry business.industry Mechanics Laser Doppler velocimetry 021001 nanoscience & nanotechnology Condensed Matter Physics Spurt flow Slip factor Volumetric flow rate Flow velocity Slip ratio 0210 nano-technology business Stick-slip |
| Zdroj: | Rheologica Acta Rheologica Acta, Springer Verlag, 2004, 43 (1), pp.89-98. ⟨10.1007/s00397-003-0323-x⟩ |
| ISSN: | 1435-1528 0035-4511 |
| DOI: | 10.1007/s00397-003-0323-x |
| Popis: | The oscillating flow instability of a molten linear high-density polyethylene is carefully studied using a single screw extruder equipped with a transparent slit die. Experiments are performed using laser Doppler velocimetry in order to obtain the local velocities field across the entire die width. At low flow rate, the extrusion is stable and steady state velocity profiles are obtained. During the instability, the velocity oscillates between two steady state limits, suggesting a periodic stick-slip transition mechanism. At high flow rate, the flow is mainly characterized by a pronounced wall slip. We show that wall slip occurs all along the die land. An investigation of the slip flow conditions shows that wall slip is not homogeneous in a cross section of the slit die, and that pure plug flow occurs only for very high flow rates. A numerical computation of the profile assuming wall slip boundary conditions is done to obtain the true local wall slip velocity. It confirms that slip velocities are of the same order of magnitude as those measured with a capillary rheometer. |
| Databáze: | OpenAIRE |
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