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RESEARCH PAPERS

In Situ Observation of Microwedge Effect on Liquid Lubrication

[+] Author and Article Information
Sy-Wei Lo, Bo-Qi Zhou, Ching-Feng Fang, Yu-Sheng Lu

Department of Mechanical Engineering, National Yunlin University of Science and Technology, Touliu, Yunlin 640, Taiwan

J. Tribol 126(4), 690-696 (Nov 09, 2004) (7 pages) doi:10.1115/1.1759338 History: Received April 08, 2003; Revised January 14, 2004; Online November 09, 2004
Copyright © 2004 by ASME
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References

Wilson, W. R. D., Malkani, H. G., and Saha, P. K., 1991, “Boundary Friction Measurements Using a New Sheet Metal Forming Simulator,” Proc. NAMRC XIX, SME, pp. 37–42.
Saha,  P. K., and Wilson,  W. R. D., 1994, “Influence of Plastic Strain on Friction in Sheet Metal Forming,” Wear, 172, pp. 167–173.
Dohda,  K., and Wang,  Z., 1995, “Investigation into Relationship Between Friction Behavior and Plastic Deformation Using a Newly Devised Rolling-Type Tribometer,” ASME J. Tribol., 117, pp. 529–533.
Dohda,  K., and Wang,  Z., 1998, “Effects of Average Lubricant Velocity and Sliding Velocity on Friction Behavior in Mild Steel Sheet Forming,” ASME J. Tribol., 120(4), pp. 724–728.
Azushima,  A., 1995, “Direct Observation of Contact Behavior to Interpret the Pressure Dependence of the Coefficient of Friction in Sheet Metal Forming,” CIRP Ann., 44(1), pp. 209–212.
Azushima,  A., Miyamoto,  J., and Kudo,  H., 1998, “Effect of Surface Topography of Workpiece on Pressure Dependence of Coefficient of Friction in Sheet Metal Forming,” CIRP Ann., 47(1), pp. 479–482.
Azushima,  A., Yoneyama,  S., Yamaguchi,  T., and Kudo,  H., 1996, “Direct Observation of Microcontact Behavior at the Interface Between Tool and Workpiece in Lubricated Upsetting,” CIRP Ann., 45(1), pp. 205–210.
Bech,  J., Bay,  N., and Eriksen,  M., 1998, “A Study of Mechanisms of Liquid Lubrication in Metal Formation,” CIRP Ann., 47(1), pp. 221–226.
Lo,  S. W., and Tsai,  S. D., 2002, “Real-Time Observation of the Evolution of Contact Area Under Boundary Lubrication in Sliding Contact,” ASME J. Tribol., 124(2), pp. 229–238.
Lo,  S. W., and Yang,  T. S., 2003, “A New Mechanism of Asperity Flattening in Sliding Contact-The Role of Tool Elastic Microwedge,” ASME J. Tribol., 125(4), pp. 713–719.
Wilson,  W. R. D., and Chang,  D.-F., 1996, “Low Speed Mixed Lubrication of Bulk Metal Forming Processes,” ASME J. Tribol., 118(1), pp. 83–89.
Lo,  S. W., and Wilson,  W. R. D., 1999, “A Theoretical Model of Micro-Pool Lubrication in Metal Forming,” ASME J. Tribol., 121(4), pp. 731–738.

Figures

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Lo and Tsai’s compression-sliding experiment 9
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Tool elastic microwedges induce multidirectional enlargement of asperity plateau. The maximum expansion occurs in the sliding direction.
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Schematic representation of the drawing experiment
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Basic experiment: longitudinal roughness; mean pressure=56 MPa; tool velocity=1 mm/s. Left: before sliding; right: sliding distance=41 mm. A is the contact area ratio.
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Basic experiment: isotropic roughness; mean pressure=56 MPa; tool velocity=1 mm/s. Left: before sliding; right: sliding distance=36, 39 mm. A is the contact area ratio.
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Basic experiment: transverse roughness; mean pressure=56 MPa; tool velocity=1 mm/s. Left: before sliding; right: sliding distance=38 mm. A is the contact area ratio.
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Basic experiment: average and initial friction coefficients versus nondimensional velocity for various roughness patterns under microwedge effect; HN and THU represent lubricants HN and THUBAN, respectively
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Basic experiment: average and initial friction coefficients versus the associated contact area ratios for longitudinal roughness
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Basic experiment: average and initial friction coefficients versus the associated contact area ratios for isotropic roughness
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Basic experiment: average and initial friction coefficients versus the associated contact area ratios for transverse roughness
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Drawing experiment: influence of tool velocity on contact area ratio in the work zone
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Drawing experiment: final contact area ratio and apparent friction coefficient versus relative sliding velocity; Dash line is the final contact area ratio estimated by the low speed mixed lubrication model 11; xN is the neutral point where high static friction stress may occur
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Drawing experiment: photos of the inlet (left) and outlet (right) regions. Drawing velocity of workpiece is 0.5 mm/s.

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