Microforming is a relatively new realm of manufacturing technology that addresses the issues involved in the fabrication of metallic microparts, i.e., metallic parts that have at least two characteristic dimensions in the sub-millimeter range. The recent trend towards miniaturization of products and technology has produced a strong demand for such metallic microparts with extremely small geometric features and high tolerances. Conventional forming technologies, such as extrusion, have encountered new challenges at the microscale due to the influence of “size effects” that tend to be predominant at this length scale. One of the factors that of interest is friction. The two companion papers investigate the frictional behavior and size effects observed during microextrusion in Part I and in a stored-energy Kolsky bar test in Part II. In this first paper, a novel experimental setup consisting of forming assembly and a loading stage has been developed to obtain the force-displacement response for the extrusion of pins made of brass (: ). This experimental setup is used to extrude pins with a circular cross section that have a final extruded diameter ranging from down to . The experimental results are then compared to finite-element simulations and analytical models to quantify the frictional behavior. It was found that the friction condition was nonuniform and showed a dependence on the dimensions (or size) of the micropin under the assumption of a homogeneous material deformation. Such assumption will be eliminated in Part II where the friction coefficient is more directly measured. Part I also investigates the validity of using high-strength/low-friction die coatings to improve the tribological characteristics observed in micro-extrusion. Three different extrusion dies coated with diamondlike carbon with silicon (DLC-Si), chromium nitride (CrN), and titanium nitride (TiN) were used in the microextrusion experiments. All the coatings worked satisfactorily in reducing the friction and, correspondingly, the extrusion force with the DLC-Si coating producing the best results.
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e-mail: jcao@northwestern.edu
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August 2007
Technical Papers
Study of the Size Effect on Friction Conditions in Microextrusion—Part I: Microextrusion Experiments and Analysis
Neil Krishnan,
Neil Krishnan
Department of Mechanical Engineering,
Northwestern University
, 2145 Sheridan Road, Evanston, IL 60201
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Jian Cao,
Jian Cao
Department of Mechanical Engineering,
e-mail: jcao@northwestern.edu
Northwestern University
, 2145 Sheridan Road, Evanston, IL 60201
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Kuniaki Dohda
Kuniaki Dohda
Department of Engineering Physics, Electronics & Mechanics,
Nagoya Institute of Technology
, Gokisocho, Showa, Nagoya 466-8555, Japan
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Neil Krishnan
Department of Mechanical Engineering,
Northwestern University
, 2145 Sheridan Road, Evanston, IL 60201
Jian Cao
Department of Mechanical Engineering,
Northwestern University
, 2145 Sheridan Road, Evanston, IL 60201e-mail: jcao@northwestern.edu
Kuniaki Dohda
Department of Engineering Physics, Electronics & Mechanics,
Nagoya Institute of Technology
, Gokisocho, Showa, Nagoya 466-8555, JapanJ. Manuf. Sci. Eng. Aug 2007, 129(4): 669-676 (8 pages)
Published Online: August 11, 2006
Article history
Received:
December 5, 2005
Revised:
August 11, 2006
Connected Content
A companion article has been published:
Study of the Size Effects and Friction Conditions in Microextrusion—Part II: Size Effect in Dynamic Friction for Brass-Steel Pairs
Citation
Krishnan, N., Cao, J., and Dohda, K. (August 11, 2006). "Study of the Size Effect on Friction Conditions in Microextrusion—Part I: Microextrusion Experiments and Analysis." ASME. J. Manuf. Sci. Eng. August 2007; 129(4): 669–676. https://doi.org/10.1115/1.2386207
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