• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.337-340
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• 2008

Magnesium alloy is expected to be widely used for mobile electronic appliances as well as automobile parts for its lightweight and EMI-shielding characteristics. In the present investigation, a Note-PC upper case made of magnesium alloy AZ31 sheet was developed by using the press forming technology at elevated temperature. Considering the press forming process and the formability of magnesium alloy sheet, the case shape and the press die was designed. The optimum forming condition was experimentally examined. Then the as-received magnesium alloy sheet was press-formed into the designed case shape under the optimum forming condition.

• Transactions of Materials Processing
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• v.18 no.2
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• pp.112-115
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• 2009

Press forming of magnesium alloy sheet is conducted at elevated temperatures to improve the press formability due to its low formability at room temperature. At elevated temperatures, magnesium alloy sheet formability is known to be very sensitive to the strain rate. In this paper, warm deep drawing tests of magnesium alloy AZ31 sheet was conducted under double forming velocity as well as single forming velocity to examine the formability change by forming velocity profile. The observed formability improvement by double forming velocity was analyzed by using the finite element analysis.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.643-648
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• 2008

Ultra-thin sheet metal forming techniques are required in precision forming of miniaturized and integrated products. In order to manufacture a good quality and low cost ultra-thin sheet metal products, a highly precise high-speed press is needed. The precision of a press is related with its vibration characteristics during pressing operation. This study evaluated the vibration characteristics of a proposed press design using computer simulation. The analysis compares the static deformation characteristics of the slide and the slide motion for the metal forming of an ultra-thin sheet of thickness less than 0.1mm. Further, in order to minimize the vibrations during high speed pressing operation, revolution balances of the eccentric shaft and the balance weight device is also considered. Finally, modal analysis is used to characterize the natural frequency of vibration of the press.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.871-872
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• 2010

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.06a
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• pp.111-131
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• 1996

In order to analyze stamping processes and to select optimum material properties of sheet steels for customer lines, 3-dimensional finite element analysis software were used. Commercial explicit finite element code, PAM-STAMP, was able to simulate 3-dimensional press formed parts with good accuracy and gave some useful results by orthogonal array experiments. Deformation of draw-bead were predicted by ABAQUS accurately, so that material selection for those parts by simulation were possible.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.378-386
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• 2010

Nowadays there has been great interest in using heat treated cast material for press dies due to several advantages like reduction in die production costs. However, in hot press forming processes H13 forged tool steel is mostly used. Cooling performance of dies in hot press forming processes is considered as an important factor of study and also the IHTC parameter between cast material die and sheet metal should be considered as an essential. In the present study, the IHTC was calculated for the sheet metal in the hot press forming process with cast and forged material dies. The temperature measurements were performed for the sheet metal, casting and forged material dies by applying various contact pressure in hot press forming. IHTC was calculated and studied by adopting the inverse heat convection method in DEFORM-2D. Each IHTC was considered as a function of contact time and contact pressure. The experimental data were compared with calculated data obtained from the proposed equation and references.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.86-93
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• 2013

Main function of the Press forming Machine is the forming for plates. The head of the Press forming machine consist of several parts. It was named Press forming-contraction and Press forming_expansion according to formability of plates. Aluminium and Titanum plates are forming by using the Press forming machine. In this study, we analyzed sheet metal forming including plastic deformation and the contact pressure in the bearing. Finite element analysis results of Press forming-contraction and Press forming_expansion show the similar results of the actual specimen plates and the bearing contact pressures show the acceptable level of stress in both aluminum and titanium specimens.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.162-169
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• 2004

In press forming of sheet metals, the material sheet is usually subjected to very large plastic strain under in-plane stressing. Moreover, the sheet also very often is subjected to out-of-plane compressive force between tools such as the upper and lower dies, the blank holder and the die, and so forth. In this paper, it is clearly demonstrated theoretically that out-of-plane stress may notably raise the forming limit strain and thus it can be effectively utilized to avoid earlier fracture of the sheet in press forming.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.387-394
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• 2006

In order to see the effect of die deformation on the forming analysis of sheet metals, the draw-ins, strains, and spring-backs of an automotive fender panels are numerically simulated by considering the die deformation found by the simultaneous structural analysis of press and dies. By coupling the forming analysis and the structural analysis, the die deformation is simultaneously taken into account in the forming process. Furthermore, for the consideration of load difference transferred among the upper die, punch, and blank holder due to the changes in sheet thickness, the gap elements are employed instead of the blank sheet in the structural analysis. The numerical simulation results of an automotive finder draw panel are compared with the measurements. The comparison of the forming and spring-back analysis results between the rigid die and the deformed die shows that the consideration of tool deformation can predict more accurately the forming and spring-back of sheet metals.

• Transactions of Materials Processing
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• v.4 no.4
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• pp.345-352
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• 1995

Warm deep drawing for optimum forming conditions to give the maximum drawing depth is investigated and compared with the results from experiments performed at room temperature. Experiments which draw square cups of STS 304 stainless steel sheet under the constant lubrication condition of teflon film are made both in a crank and hydraulic press for two kinds of specimens. The maximum drawing depth at warm forming condition reaches 1.4 times the drawing depth at room temperature in a crank press, whereas 1.6 times in a hydraulic press, and also more uniform distribution of thickness in case of warm deep drawn cup is observed. The effects of other factors on formability, such as forming temperature, speed of press and cooling of punch are examined and discussed.