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Martin Kroger
Fluid dynamics: theory, computation, and numerical simulation (C. Pozrikidis)

Appl. Rheol. 12:2 (2002) 105-106

Cite this publication as follows:
Kroger M: Fluid dynamics: theory, computation, and numerical simulation (C. Pozrikidis), Appl. Rheol. 12 (2002) 105.

Evdokia Achilleos, Georgios C. Georgiou, Savvas G. Hatzikiriakos
On numerical simulation of polymer extrusion instabilities

Appl. Rheol. 12:2 (2002) 88-104

The objective of this study is mainly to review recent work concerning the numerical modeling of the stick-slip and gross melt fracture polymer extrusion instabilities. Three different mechanisms of instability are discussed: (a) combination of nonlinear slip with compressibility; (b) combination of nonlinear slip with elasticity; and (c) constitutive instabilities. Furthermore, preliminary numerical simulations of the time-dependent, compressible extrudate-swell flow of a Carreau fluid with slip at the wall, using a realistic macroscopic slip equation that is based on experimental data for a high-density polyethylene, are presented.

Cite this publication as follows:
Achilleos E, Georgiou GC, Hatzikiriakos SG: On numerical simulation of polymer extrusion instabilities, Appl. Rheol. 12 (2002) 88.

Christophe Baravian, Audrey Lalante, Alan Parker
Vane rheometry with a large, finite gap

Appl. Rheol. 12:2 (2002) 81-87

The vane geometry with a large gap is used to determine the Newtonian, non-Newtonian and viscoelastic properties of complex fluids. We show that when this geometry is carefully characterized, it can be used for precise rheometry. A novel effective cylinder approximation is used to obtain the shear rate and shear stress factors. The effective radius is found to be close to the height of the triangle formed by joining the tips of adjacent blades. This result differs significantly from that of previous work. Flow visualization has been used to confirm that the stream lines bend towards the centre between the blades. These factors can be used to determine the flow curves of non-Newtonian liquids, using Krieger.s power law expansion. The standard procedure for using the vane to determine the yield stress is also carefully investigated and alternative procedures are suggested.

Cite this publication as follows:
Baravian C, Lalante A, Parker A: Vane rheometry with a large, finite gap, Appl. Rheol. 12 (2002) 81.

Tomas Honek, Berenika Hausnerova, Petr Saha
Temperature dependent flow properties of powder injection moulding compounds

Appl. Rheol. 12:2 (2002) 72-80

The temperature dependent flow properties of highly filled polymer compounds intended for production of hard-metal parts by powder injection moulding (PIM) technology were studied. The pure binder based on polyethylene, ethylene and butyl acrylate block copolymer and paraffin, and its compounds with hard-metal carbide powder (up to 55 vol. %) were prepared by melt mixing at 180.C. The flow properties were investigated at the temperature range from 140.C to 200.C using capillary rheometer operating flow at a constant piston speed. The measure of temperature sensitivity of PIM compounds, activation energy of shear flow, decreases with powder loading and shear rate. The Arrhenius relation for these materials is only valid in the stable flow region. At the temperatures above 170.C the compounds filled with 45 vol. % carbide powder and higher exhibit an unstable flow of pressure oscillations type at the shear rates above 103 s-1. The onset of pressure oscillations is strongly affected by temperature. The relation between critical shear stress for the onset of pressure oscillations and temperature is non-linear.

Cite this publication as follows:
Honek T, Hausnerova B, Saha P: Temperature dependent flow properties of powder injection moulding compounds, Appl. Rheol. 12 (2002) 72.


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