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Research Papers: Friction & Wear

The Effect of Surface Conditions on Friction by Tip Test

[+] Author and Article Information
Ki-Ho Jung, Hyun-Chul Lee, Joseph S. Ajiboye

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Gusong-dong, Yusong-gu, Daejeon 305-701, Korea

Seong-Hoon Kang

Department of Materials Processing, Applied Plasticity Research Group, Korea Institute of Materials Science, 531 Changwondaero, Changwon, Kyungnam 641-831, Korea

Yong-Taek Im1

Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Gusong-dong, Yusong-gu, Daejeon 305-701, Koreaytim@kaist.ac.kr

1

Corresponding author.

J. Tribol 132(1), 011601 (Nov 09, 2009) (7 pages) doi:10.1115/1.4000273 History: Received April 27, 2009; Revised August 25, 2009; Published November 09, 2009; Online November 09, 2009

In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of a tip test experimental setup

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Figure 2

Surface topology of the punch measured by a white-light scanning interferometer microscope

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Figure 3

Surface topology of the smooth counter punch measured by a confocal laser microscope (Olympus OLS-3000) before the experiment

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Figure 4

Surface topology of the rough counter punch measured by a white-light scanning interferometer microscope before the experiment

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Figure 5

Progressive deformation of the initial specimen depending on the strokes

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Figure 6

Definition of the tip distance d, and a deformed specimen obtained from the experiment

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Figure 7

Load versus punch stroke curves in the tip tests of AL6061-O with different surface and lubrication conditions

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Figure 8

Load versus punch stroke curves in the tip tests of AL2024-O with different surface and lubrication conditions

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Figure 9

Combined plots of normalized maximum load versus tip distance of AL6061-O and AL2024-O, respectively

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Figure 10

Comparison of surface topologies at the bottom of specimens between the initial and deformed one at the stroke of 1.6 mm of AL6061-O and AL2024-O, respectively

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Figure 11

Surface topology of the rough counter punch measured by a white-light scanning interferometer microscope after the experiment

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Figure 12

The slope change in the plot of dimensionless load versus tip distance, depending on x=mfd/mfp values

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Figure 13

Combined experimental and simulated plots of normalized maximum load versus relative tip distance of AL6061-O and AL2024-O (here, x=mfd/mfp)

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Figure 14

Tip generation depending on surface topology

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Figure 15

Shear friction factors at the punch associated with the dimensionless tip distance with different surface topologies of the counter punch

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Figure 16

Shear friction factors at the counter punch associated with dimensionless tip distance with its different surface topologies

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