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Research Papers

Finite Element Analysis of Plastic Strain Distribution in Multipass ECAE Process of High Density Polyethylene

[+] Author and Article Information
B. Aour1

Département de Mécanique, Laboratoire de Recherche en Technologie de l’Environnement, ENSET d’Oran, BP1523 El’Mnaour 31000, Algeria; Laboratoire de Mécanique de Lille, UMR CNRS 8107, USTL, Polytech’Lille, Avenue P. Langevin, 59655 Villeneuve d’Ascq Cedex, Franceben_aour@hotmail.com

F. Zaïri1

Laboratoire de Mécanique de Lille, UMR CNRS 8107, USTL, Polytech’Lille, Avenue P. Langevin, 59655 Villeneuve d’Ascq Cedex, Francefahmi.zairi@polytech-lille.fr

M. Naït-Abdelaziz

Laboratoire de Mécanique de Lille, UMR CNRS 8107, USTL, Polytech’Lille, Avenue P. Langevin, 59655 Villeneuve d’Ascq Cedex, France

J. M. Gloaguen, J. M. Lefebvre

Laboratoire de Structure et Propriétés de l’Etat Solide, UMR CNRS 8008, USTL, Bâtiment C6, 59655 Villeneuve d’Ascq Cedex, France

1

Corresponding authors.

J. Manuf. Sci. Eng 131(3), 031016 (May 29, 2009) (11 pages) doi:10.1115/1.3139217 History: Received September 16, 2007; Revised March 23, 2009; Published May 29, 2009

Equal channel angular extrusion (ECAE) is a relatively novel forming process to modify microstructure via severe plastic deformation without modification of the sample cross section. In this study, an optimized design of die geometry is presented, which improves homogeneity of the plastic deformation and decreases the pressing force required for extrusion. Then, a typical semicrystalline polymer (high density polyethylene) was subjected to multipass ECAE using two different processing routes: route A where the sample orientation is kept constant between passes and route C where the sample is rotated by 180 deg. Compression tests at room temperature and under different strain rates were used to identify the material parameters of a phenomenological elastic-viscoplastic model. Two-dimensional finite element analysis of ECAE process was carried out, thus allowing to check out the homogeneity of the plastic strain distribution. The effects of die geometry, number of passes, processing route, and friction coefficient on the plastic strain distribution were studied. The simulations were performed for three channel angles (i.e., 90 deg, 120 deg, and 135 deg), considering different corner angles. According to simulation results, recommendations on the angular extrusion of the polymer are provided for improving die and process performance.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic illustration of (a) a typical ECAE facility and (b) the processing routes A, B, and C

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Figure 2

Schematic illustration of the modified die geometry introducing a curved profile: (a) θ=θmax and (b) 0≤θ≤θmax

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Figure 5

Comparison between FEM and analytical solutions of the equivalent plastic strain according to various die angles

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Figure 6

Effect of corner angle θ on the equivalent plastic strain for (a) Φ=90 deg, (b) Φ=120 deg, and (c) Φ=135 deg

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Figure 7

Actual ECAE force required to push the HDPE sample at Φ=90 deg with different corner angles θ in relation to the sample positions

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Figure 8

Comparison of the distribution of the equivalent plastic strain between the sharp inner angle at point O and a round inner angle when (a) θ=5 deg and (b) θ=θmax (the variation factor V for each geometry is plotted at the top of the figure)

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Figure 9

FEM simulations of the equivalent plastic strain in the case of 135 deg die with (a) route A and (b) route C

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Figure 10

Effect of extrusion number on the distribution of equivalent plastic strain in the case of route A with (a) 90 deg die, (b) 120 deg die, and (c) 135 deg die

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Figure 11

Variation of the equivalent plastic strain at midpoint of cross section as function of number of passes

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Figure 12

Effect of the processing route on the distribution of equivalent plastic strain for (a) 90 deg die, (b) 120 deg die, and (c) 135 deg die

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Figure 13

Evolution of the equivalent plastic strain in terms of the number of passes in the case of route A for (a) 90 deg die, (b) 120 deg die, and (c) 135 deg die with a corner angle of 5 deg and θmax

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Figure 14

Effect of friction coefficient on the equivalent plastic strain distribution after six passes (in route A) for (a) Φ=90 deg and θ=5 deg, (b) Φ=120 deg and θ=5 deg, (c) Φ=135 deg and θ=5 deg, (d) Φ=90 deg and θ=64 deg, (e) Φ=120 deg and θ=45 deg, and (f) Φ=135 deg and θ=34 deg

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Figure 3

Variation of the equivalent plastic strain versus die angles Φ and θ given by analytical expressions

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Figure 4

Stress-strain curves of HDPE at room temperature

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