• Proceedings of the KSME Conference
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• 2001.06c
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• pp.616-620
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• 2001

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding force(BHF), but BHF affects the draw depth. Although the wrinkles of flange have been made in the incipient stage of drawing, if the height of wrinkles is maintained under a prescribed limit by decrease or extinction of wrinkles in the course of drawing, small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of square cup drawing by using aluminium A1015 and aluminium alloy A5052.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.3
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• pp.276-282
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• 2009

Wrinkling in the flange and wall of a deep-drawn part is one of the major defects in sheet metal processes. Wrinkling is influenced by many factors, such as material properties, shape of the body, forming conditions, stress state and thickness, etc. It is difficult to analyze the wrinkling initiation and growth according to the factors because the effects of the factors are very complex and the wrinkling behavior may show wide variation even though small deviation of factors. In this study, the influence of wrinkling parameters, such as material properties (Al1050, Al5052), the blank holding force and the drawing depth on the wrinkling initiation and growth is investigated by using the experimental method and the dynamic explicit finite element analysis. From the results, it is shown that the dynamic explicit finite element method can be used effectively to prevent the wrinkling problems advancely in the deep drawing process. Also, there is a good agreement between the experimental result and the dynamic explicit finite element analysis.

• Transactions of Materials Processing
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• v.8 no.4
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• pp.356-363
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• 1999

This paper discusses some techniques for the determination of optimum blank size and pre-form design for multi-stepped deep drawing of oval shell. The deep drawing process of oval shape has been regarded as more difficult than that of cylindrical shell because of its complicated behavior of plastic deformation. But there is insufficient information in this area to carry out successful deep drawing work of irregular products such as oval, rectangular, and square shapes. In order to find the optimum conditions, the drawing apparatus for two kinds of pre-form design are built, a series of drawing experiments performed, and thickness stain distributions measured. From the results of thess suggested experiments, various optimum process variables are observed and discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.394-396
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• 2007

In this study, in order to see effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions, such are lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and performed the friction test in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases maximum 30% as the blank holding force and the drawing speed are increased to 2.5kN and 1500mm/min, respectively.

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.381-385
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• 2007

In order to examine the effect of the blank holding force on the friction behavior in the sheet metal forming, a sheet metal friction tester is designed and manufactured, which can measure friction forces in various forming conditions such as lubrication, die roughness, drawing speed, radius of die corner, blank holding force, etc., and the friction tests are performed, in which friction coefficients in various blank holding forces and pulling speeds are calculated using Coulomb's friction law. The friction test reveals that friction coefficient decreases as the blank holding force, the drawing speed and lubricant viscosity increase together or individually.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.8-12
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• 2012

This study aims to analyze the formability property of surface texturing processed automotive steel sheet for improving the sheet forming property. In the paper, the effect of cavities fabricated using the laser surface texturing technique on automotive high strength steel sheets was studied. The frictional behavior of the sheet drawing is a function of interface parameters such as sheet surface roughness, holding force, contact pressure, etc. For these reasons, automotive steel researchers want to optimize the surface topography of automotive steel sheets in order to enhance the formability. Therefore, this study presents the behavior of deformation of a laser surface texturing steel sheet by considering the frictional operation during the deep drawing process.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.274-282
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• 2009

To investigate the evolution of deformation texture in dual phase (DP) steels during deep-drawing deformation, deep-drawing experiments were performed. Microtexture measurements were conducted using electron backscattered diffraction (EBSD) to analyze texture evolution. A rate-sensitive polycrystal model was used to predict texture evolution during deep-drawing deformation. In order to evaluate the strain path during deep-drawing deformation, a steady state was assumed in the flange part of a deep-drawn cup. A ratesensitive polycrystal model successfully predicted the texture evolution in DP steels during deep-drawing deformation. The final stable orientations were found to be strongly dependent on the initial location in the blank. Texture analysis revealed that the deep drawability of DP steels decreases as the true strain in the radial direction of the deep-drawn cup increases during deep-drawing deformation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1313-1314
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.845-848
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• 2002

The wrinkling in the flange and wall of a part is a predominent failure mode in stamping of sheet metal parts. In many cases this wrinkling may be eliminated by appropriate control of the blank holding forco(BHF), but BHF affects the draw depth. Gotoh had studied the wrinkles under 0.02mm in height. In general, the height of wrinkles could be limited under 0.2mm practically. Therefore small BHP can be allowed so that the depth of drawing could be increased. Authors research the variation of the wrinkles in flange in the course of cup drawing by using aluminium alloy Al050 and A5052.

• Korean Journal of Metals and Materials
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• v.46 no.8
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• pp.489-494
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• 2008

The effect of drawing rate on the electrochemical properties of 3003 Al alloys in 5 wt.% NaCl solution was investigated by electrochemical techniques (potentiodynamic polarization test, potentiostatic polarization test, electrochemical impedance spectroscopy (EIS)) and surface analyses (OM, SEM, EDS). Four kinds of automotive pipe materials were prepared (raw material, drawing rate = 5, 10, 15%). As the drawing rate of Al alloy tube increased, the pitting corrosion resistance increased due to the enrichment of Al oxides on the surface.