Yes / An approximation to the Phan-Thien Tanner (PTT) constitutive model is
developed with the aim of giving low-cost simulation of Gas Assisted Injection Moulding
(GAIM) while incorporating important viscoelastic characteristics. It is shown that the
developed model gives a response typical of full viscoelastic models in transient and steady state
uniaxial and constant shear rate deformations. The model is incorporated into a 3D
finite element GAIM simulation which uses the ‘pseudo-concentration’ method to predict
residual polymer, and applied to published experimental results for a Boger fluid and a
shear-thinning polystyrene melt.
It is shown that the simulation gives a very good match to published results for the Boger
fluid which show increasing Residual Wall Thickness (RWT) with increasing Deborah
number. Against the shear-thinning polymer, the quality of match depends upon which of two
‘plausible’ relaxation times is chosen; qualitatively different results arise from two different
means of estimating a single relaxation time. A ‘multi-mode’ approach is developed to avoid
this uncertainty. It is shown that the multi-mode approach gives decreasing RWT with
increasing Deborah number in agreement with the published experimental results, and
avoids the issues that arise from estimating a single relaxation time for a molten polymer.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/17633 |
| Date | 06 February 2020 |
| Creators | Olley, Peter |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Article, Accepted manuscript |
| Rights | © 2020 Elsevier B.V. All rights reserved. Reproduced in accordance with the publisher's self-archiving policy. This manuscript version is made available under the CC-BY-NC-ND 4.0 license. |
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