Modeling Cutting: Plastic Deformation of Polymer Samples Indented With a Wedge

[+] Author and Article Information
Richard R. Meehan1

Materials Science Program, Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627-0133

S. J. Burns

Materials Science Program, Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627-0133


Present address: 4200 Purviance Court, Wilmington, NC 28409.

J. Manuf. Sci. Eng 129(3), 477-484 (Nov 01, 2006) (8 pages) doi:10.1115/1.2716716 History: Received June 07, 2006; Revised November 01, 2006

An experiment was designed to relate force to plastic deformation caused by a wedge indenting the edge surface of a polymer sample. The experiment reveals the primary phenomena observed in industrial converting processes of cutting and slitting of thin polymer films. The thin film was modeled using a polycarbonate rectangular block, which was indented with a metallic half-round wedge that represents the industrial cutter blades. The wedge radius and sample size were selected to scale to the ratio of slitting blade radius and industrial film thickness. A compression test frame impressed wedges into polymer samples with measurements of both force and displacement recorded. These experiments clearly revealed the shape of the plastic deformation zone ahead of and around the wedges. Data from the experiments showed increasing cutting force with wedge displacement until the sample fractured. Plastic deformation of the samples was examined: the out-of-plane plastic volume was shown to equal the volume displaced by the wedge. Cracks that developed from the side of the wedge tip during indention propagated with near steady-state loads under edge surface indention.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 7

A crack is visible through the sample thickness at an angle to the plane of the wedge. Cracks develop in the tensile region near the tip of the wedge.

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Figure 5

(a) Out-of-plane plastic deformation viewed from a top corner view and (b) out-of-plane plastic deformation viewed from the sample top where it was wedge loaded

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Figure 6

Cutting force versus wedge displacement: The cracking, which is initiated at the wedge, reduces the steady-state cutting force to approximately one-half of the maximum plastic deformation force

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Figure 10

Hardness and yield stress versus wedge displacement

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Figure 11

Load versus displacement for comparison of finite element model and experimental data from Fig. 6.

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Figure 12

FEA von Mises stress contours at wedge displacements of (a) 0.026in., (b) 0.046in., and (c) 0.10in., respectively

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Figure 13

Tangential stresses in polar coordinates with 0.100in. wedge displacement

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Figure 1

Experiments were conducted using a compression apparatus mounted within the frame of a screw-driven test frame. The upper cross-head pushes the polycarbonate sample onto the knife; it is in series with a load cell. Displacements are measured on the right with an LVDT.

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Figure 2

Finite element model showing 1∕4 of the indented solid

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Figure 3

The out-of-plane plastic deformation zone is clearly visible ahead of the wedge indention (scale in centimeters)

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Figure 4

Plastic deformation zone radius R versus cutting force per unit thickness F∕t

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Figure 8

Geometry of indenting wedge

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Figure 9

Load versus projected area of indenting wedge



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