Melting in a Single Screw Extruder: Experiments and 3D Finite Element Simulations
(182-196)  International Polymer Processing #2 (2011)
Altınkaynak et al ofMichigan Technological University and Dow Chemical, Michigan, simulated the melting of an ABS resin using a three-dimensional finite element simulation of the two-phase flow in the compression section of a single-screw extruder.  Screw freezing experiments were also conducted to compare the numerical predictions with the corresponding experimental data.  Numerical simulations as well as experiments exhibited the Maddock melting mechanism and numerical predictions were in good agreement with the corresponding experimental data.  The sensitivity of the melting profile to various material properties and processing conditions was numerically analyzed.  With a constant flow rate enforced at the entrance of the screw channel, the screw and barrel temperature were found to have a minor effect on the melting profile.  However, these parameters were found to have a significant effect on the predicted pressure profile along the screw channel.  When the zero-traction boundary condition was imposed at the entrance of the screw channel, a change in the screw or barrel temperature affected the flow rate in the screw channel, which resulted in a significant change in the solid fraction at the same cross-section.  (RDC 5/23/2011)

Investigation of combination of finite element formulation and element type on the accuracy of 3D modeling of polymeric fluid flow in an extrusion die
 (1607–1615)Journal of Applied Polymer  Science 120 #3 (2011)
Sobhani et al of the Iran Polymer and Petrochemical Institute, Iran studied computer models based on three finite element solution schemes (mixed, continuous, and discrete penalty), and two element types (hexahedral and tetrahedral) in a 3D framework were developed. The well-known Carreau model was used to reflect the rheological behavior of the fluid. To determine the validity of the developed computer simulations, the flow of two high-density polyethylene (HDPE) melts with different viscosities through an extrusion die was simulated and compared with experimentally measured data. Comparison showed that the three methods produced nearly the same results with the hexahedral elements.  However, continuous penalty method using tetrahedral elements demonstrated an extreme discrepancy from the experimental data. Discrete penalty method was unable to predict secondary variable (pressure) accurately using tetrahedral elements. The best results were obtained by the use of mixed methods in conjunction with tetrahedral elements. (RDC 2/16/2011)