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Comparison of One-Hole Die Shape

Fermi National Accelerator Laboratory(FNAL)

Department of Mechanical Engineering Northern Illinois University

Northern Illinois Center for Accelerator and Detector Development

(NICADD)

By

Dr. Meung Kim & Prasad Rayasam

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

Desired Dimensions of the Extrudate

Units: CM

0.11

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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.”

5No.of elements on this face = 450Model Half Domain

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.

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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.

Mesh Refinement: Half Domain

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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

Other Team

Our Team

Existing

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Sample Extrudate: Experiment

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_extrusion_samples_11-13-03.pdf

(a) (b)

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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

1.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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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

Material Parameters - Styron 663add

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Styron 663add

Zero-Shear Rate Viscosity

0.1471E+5 0.603E+4

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

Material Parameters

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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