Simulation of the gas-assisted injection moulding process using a viscoelastic extension to the Cross-WLF viscosity model

An approximation to the viscoelastic Maxwell model is developed and combined with a Cross-WLF shear- and temperature-dependent model as a means of introducing aspects of viscoelasticity into the Cross-WLF model at a low computational cost. The main objective of the model is to simulate the gas-assis...

Full description

Saved in:
Bibliographic Details
Published in:Proceedings of the Institution of Mechanical Engineers. Part E, Journal of process mechanical engineering Journal of process mechanical engineering, 2011-11, Vol.225 (4), p.239-254
Main Authors: Olley, P, Mulvaney-Johnson, L, Coates, P D
Format: Article
Language:English
Subjects:
Computer simulation
Gases
Injection molding
Mathematical analysis
Mathematical models
Residual stress
Shear
Simulation
Temperature dependence
Three dimensional
Viscoelasticity
Viscosity
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:An approximation to the viscoelastic Maxwell model is developed and combined with a Cross-WLF shear- and temperature-dependent model as a means of introducing aspects of viscoelasticity into the Cross-WLF model at a low computational cost. The main objective of the model is to simulate the gas-assisted injection moulding (GAIM) process with the aspect of a material's strain history included. It is shown that the model gives a transient and steady response comparable to the Doi–Edwards viscoelastic model in constant rate shear and uniaxial deformations, and follows WLF temperature dependence. The model is implemented in a three-dimensional finite element code using the ‘pseudo-concentration’ method to model the polymer and gas phases. The ordinary Cross-WLF model had demonstrated a consistent under-prediction of residual wall thickness (RWT) measurements in comparison to experimental results. It is shown that the viscoelastic extension to the Cross-WLF model gives a marked increase in RWT and exhibits aspects of stress relaxation and history dependence. The model is tested against variations of other process control parameters. It is shown that the simulation gives the correct qualitative response for all control parameters assessed, with quantitative prediction within a factor of 2.
ISSN:0954-4089
2041-3009
DOI:10.1177/0954408911409134