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TECHNICAL PAPERS

On the Use of a Kolsky Torsion Bar to Study the Transient Large-Strain Response of Polymer Melts at High Shear Rates

[+] Author and Article Information
Y. Hu, R. Feng

Department of Engineering Mechanics, University of Nebraska-Lincoln, Lincoln, NE 68588-0526

J. Appl. Mech 71(4), 441-449 (Sep 07, 2004) (9 pages) doi:10.1115/1.1756142 History: Received September 06, 2001; Revised November 20, 2003; Online September 07, 2004
Copyright © 2004 by ASME
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References

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Figures

Grahic Jump Location
Schematic of KTB rheometric experiment. (a) Experimental setup based on a Kolsky torsion bar system. (b) Torsional wave propagation during the experiment.
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Schematic of the rheometer assembly. (a) Thermal chamber and asymmetrically paired bars. (b) Cone-and-plate rheometric cell.
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Shear rate and shear stress profiles from a typical KTB rheometric experiment on the DuPont-20 LDPE melt at 190°C. The thicker line with respect to the left axis is the rate profile. The thinner line with respect to the right axis is the stress profile.
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Comparison of shear stress measurements with and without thin Teflon film. The initial temperatures for both experiments were 190°C. The solid line is the measurement with Teflon film and under a plateau shear rate of 3900 s−1 . The broken line is the measurement without Teflon film and under a plateau shear rate of 3970 s−1 .
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Shear stress profiles for various shear rates and 190°C initial temperature
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Shear stress-shear strain relations for various shear rates and 190°C initial temperature. The circles indicate the maximum shear strains reached in the experiments.
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Variation of transient response with initial temperature. The mean plateau shear rate is 3990 s−1 and the deviation is ±90 s−1 .
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Viscous stress jumps for various shear rates and 190°C initial temperature
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Comparison of the ratios of shear stress to shear rate with the apparent shear viscosity results on similar LDPE melts. The squares are the steady-state data and estimates for the DuPont-20 LDPE melt at 190°C. The triangles are the results corrected for the shear strain hardening. The circles and the broken line are respectively the capillary results of the apparent shear viscosity of a PEMEX LDPE melt, 6, and that of a Union Carbide LEDP melt, 14, both at 190°C.

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