Analysis Of Polymer Flow In Extrusion Dies For Scintillator

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Comparison of One-Hole Die Shape
Northern Illinois Center for Accelerator and
Detector Development (NICADD)
Fermi National Accelerator Laboratory (FNAL)
By Dr. Meung Kim Prasad Rayasam
Department of Mechanical Engineering Northern
Illinois University
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Contents

1. Objective Dimensions of Extrudate
2. Inverse Analysis with Remeshing
3. Mesh Refinement Study
4. Calibrator
5. Material Parameters

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Objective Dimensions of the Extrudate
Units CM
Desired Dimensions of the Extrudate
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Inverse Analysis with Remeshing

• According to PolyFlow manual three sections must
  be modeled as
• For the section to be maintained at a constant
  shape, constant section for prediction is
  selected instead of Adaptive section for
  prediction. POLFYLOW is to compute the shape
  (referred to as the adaptive section of the die),
  based on the specified extrudate shape.

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Mesh Refinement Study

• Mesh refinement in two different directions
  along the longitudinal direction and transverse
  direction.
• The inlet of adaptive section is updated based on
  constant section obtained by inverse analysis.

Model Half Domain
No.of elements on this face 450
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Mesh Refinement Half Domain

• Max no.of elements is limited by memory
• Much better ear shape is observed using more
  elements.
• In all cases the initial adaptive section that
  was rectangular is modified similar to constant
  section after inverse analysis to get smooth
  transition.

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Mesh Refinement Quarter Domain
Model Quarter domain (Final Result) with 1.5
inches of free surface
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Comparison of Profiles
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Sample Extrudate Experiment
(a)
(b)
Both profiles of the sample extrudates measured
by (a) our team and (b) the other team 1 are
much larger than objective size (2 x 1 cm) of
extrudate.
1 http//www.kostic.niu.edu/extrusion/scanned_ex
trusion_samples_11-13-03.pdf
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Comparison of Desired and Simulated Extrudate by
Direct Extrusion
Case B in previous quarter domain simulation
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Comparison Die Section Dimensions (mm)
Center Width Center Height Major Hole Dia. Minor Hole Dia.
Existing Die 20.312 9.54 1.22 1.22
Our Team 18.825 9.155 0.955 0.69
Other Team 20.004 9.788 1.054 0.77
Experimental 22.5 11.2 1.4 0.93
Our Simulated 19.97 9.956 0.99 0.992
Objective 20 10 1.1 1.1
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Observations Discussion

1. Existing Die gives Larger Dimensions of the
   Extrudate than Objective with Rounded Corners.
2. For Desired Extrudate of 2 x 1 cm² with 90º
   Corners, it seems that the die must be smaller
   and needs to have ears as shown in our simulation.

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Observations Discussion

• The simulation is based on rigorous computational
  analysis.
• Convergence analysis in x-y and z-directions was
  performed until converged result was obtained.
• Consistent to standard extrusion analysis, three
  sections of transition, constant, and
  free-surface were used to make sure that the
  extrudate remains constant after the end of free
  surface.
• A material function fits the experimental data
  for all temperatures.
• Gravitational effect has been checked out to be
  negligible.
• Though isothermal and non-isothermal simulations
  give closer results, non-isothermal simulations
  with temperature-dependent viscosity are carried
  out.
• Improving adaptive section after inverse
  analysis.
• Use long enough length of free surface to insure
  that the velocity remains constant.

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Material Parameters - Styron 663add
Polymat is used to curve fit the viscosity
shear rate data using Carreau Yasuda law for
Styron 663add at three different temperatures
using Arrhenious Shear stress law.
Plot of polymer viscosity as a function of shear
rate and temperature
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Material Parameters
Styron 663add Styron 663add
Zero-Shear Rate Viscosity 0.1471E5 0.603E4
Infinite Shear Rate Viscosity 0.433E-7 0.757E-3
Natural Time 0.5538 0.228
Slope 0.3263 0.3269
Transition Parameter 0.9419 0.946
alfa (temp) 17070 17038
Talfa (ref) 473 485
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Face Mesh
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Transition Region
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Exploded view of Assembly
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2-D Drawing for Top Die
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2-D Drawing for Pin
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Inlet Die Lip
Transition Lip
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Thank You