• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1129-1137
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• 1990

Based on the formulation which incorporates large deformation and anisotropy, an elastic-plastic finite element code is developed with membrane element to include the contact treatment. For the analysis of the general sheet metal forming process with contact condition, the treatment of contact is considered by employing the successive skew coordinate system. Three kinds of sheet metal forming processes with contact conditions are analyzed; stretching of a square diaphragm with a hemispherical punch, deep drawing of a circular cup and deep drawing of a square cup. Then the computational results are compared with the experiment. The computed loads and the distribution of the thickness strain are in good agreement with the experiment for all cases. However, the computational results of the thickness strain show the effect of bending can not be ignored in the deep drawing process whereas the effect of bending is negligible in stretching.

• Transactions of Materials Processing
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• v.21 no.4
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• pp.258-264
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• 2012

The forming failure of AZ31 alloy sheet during deep drawing processes was predicted by the FEM and ductile fracture criteria. Uniaxial tensile tests of round-notched specimens and FE simulations were performed to calculate the critical damage values for three ductile fracture criteria. The critical damage values for each criterion were expressed as a function of strain rate at various temperatures. In order to determine the best criterion for failure prediction, Erichsen cupping test under isothermal conditions at $250^{\circ}C$ were conducted. Based on the plastic deformation histories obtained from the FE analysis of the Erichsen cupping tests and the critical damage value curves, the initiation time and location of fracture were predicted under bi-axial tension deformation. The results indicate that the Cockcroft-Latham criterion had good agreement with the experimental data. In addition, the FE analysis combined with the criterion was applied to another deep drawing process using an irregular shaped blank and these additional results were verified with experimental tests.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.598-603
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• 2001

For metal forming analysis, upper-bound solution is practical method because the solution is overestimated. It is limited to determine stresses on tools by using upper-bound solution. In this study, new scheme to calculate stresses on tools based on upper bound solution is proposed. To verify the proposed scheme, plane strain drawing has been considered. The stresses on tools obtained by the proposed scheme are compared with results of rigid plastic FEM. And the stresses on tools have been determined by the proposed scheme in the forging within plane strain deformation.

• Transactions of Materials Processing
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• v.25 no.6
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• pp.390-395
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• 2016

GDI fuel rail is component of GDI system which directly fuel with high pressure in the engine combustion chamber. And it is required to high strength and dimensional accuracy. Multi roll-die drawing process consists of the idle roll-die and drawing die in tandem. In the course of drawing with roll-die, deformation takes place between the idle roller pair or pairs. The friction force decreases with the idle roll-die, enabling the reductions to be risen in one step. In this study, the caliber of 4-roll was designed into pass schedule that made the draw force at the exit of the drawing die be equal. In order to compensate for over-filling area, the roll caliber was modified using the result of FE-analysis. The results of FE-analysis and experiment show that the proposed design method can be used to effectively design the multi roll-die process, leading to an accurate shape and correct dimensions of the final within an allowable tolerance of ${\pm}0.08mm$. Furthermore, the productivity was evaluated by comparing with multi roll-die drawing process and conventional multi shape drawing process. The result was confirmed that it has an efficiency of about 2 times than conventional process in terms of time.

• Transactions of Materials Processing
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• v.8 no.4
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• pp.340-346
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• 1999

Circular drawbead forming and drawing characteristics of CO2 laser welded SPC1 blanks are investigated by experiments and numerical analysis. During the drawbead forming process, the distributions of major strain on upper and lower skins of the specimens are measured. During the drawing process, the drawing forces and the strain distributions are investigated. For the numerical analysis. DYNA3D and SGTAS, a developed rigid-plastic finite-element computer program are used. Numerical results predicted the deformation characteristics well in comparison with experiments. It is concluded that the strains and restraining forces during the forming and the drawing processes show different patterns according to the combination of welded blanks.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.35-40
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• 2014

Wire drawing is aplastic deformation process that produces a wire with a desired diameter by pulling the end of the wire through a die. During the cold wire drawing process, the temperature between the wire and the die bearing is increased. This temperature increase causesenergy consumption increase, bad wire quality, and decreased die life. To reduce friction and avoid high temperature between the wire and the die in the cold wire drawing process, a dry lubricant with soap particles is used. It is not possible to reused the lubricant onceiron oxide is attached to the soap particlesat high pressure die. In this study, recycling technologies for wasted soap particles with processes of crushing, separation, and screening are developed. From the evaluation, the recycling efficiency was found to be 86.97%.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.46-49
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• 2003

Cu have been widely used as signal transmission materials for electrical electronic components owing to its high electrical conductivity. However, it's size have been limited to small ones due to its poor mechanical properties, Until now, strengthening of the copper at toy was obtained either by the solid solution and precipitation hardening by adding alloy elements or the work hardening by deformation process. Adding the at toy elements lead to reduction of electrical conductivity. In this aspect, if carbon nanofiber is used as reinforcement which have outstanding mechanical strength and electric conductivity, it is possible to develope Cu matrix nanocomposite having almost no loss of electric conductivity. It is expected to be innovative in electric conduct ing material market. The unidirectional alignment of carbon nanofiber is the most challenging task developing the copper matrix composites of high strength and electric conductivity In this study, the unidirectional alignment of carbon nanofibers which is used reinforced material are controlled by drawing process in order to manufacture the intermediary materials for the carbon nanofiber reinforced Cu matrix nanocomposite and align mechanism as well as optimized drawing process parameters are verified via experiments and numerical analysis. The materials used in this study were pure copper and the nanofibers of 150nm in diameter and of $10~20\mu\textrm{m}$ In length. The materials have been tested and the tensile strength was 75MPa with the elongation of 44% for the copper it is assumed that carbon nanofiber behave like porous elasto-plastic materials. Compaction test was conducted to obtain constitutive properties of carbon nanofiber. Optimal parameter for drawing process was obtained by experiments and numerical analysis considering the various drawing angles, reduction areas, friction coefficient, etc Lower reduction areas provides the less rupture of cu tube is not iced during the drawing process. Optimal die angle was between 5 degree and 12 degree. Relative density of carbon nanofiber embedded in the copper tube is higher as drawing diameter decrease and compressive residual stress is occurred in the copper tube. Carbon nanofibers are moved to the reverse drawing direct ion via shear force caused by deformation of the copper tube and alined to the drawing direction.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.49-57
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• 2012

It is difficult to estimate the properties of multilayered sheet because they are composed of one or more different materials. Plastic deformation behavior of the multilayered sheet is quite different as compared to each material individually. The deformation behavior of multilayered sheet should be investigated in order to prevent forming defects and to predict the properties of the formed part. In this study, the mechanical properties and formability of stainless steel-aluminum-magnesium multilayered sheet were investigated. The multilayered sheet needs to be deformed at an elevated temperature because of its poor formability at room temperature. Uniaxial tensile tests were performed at various temperatures and strain rates. Fracture patterns changed mainly at a temperature of $200^{\circ}C$. Uniform and total elongation of multilayered sheet increased to values greater than those of each material when deformed at $250^{\circ}C$. The limiting drawing ratio (LDR) was obtained using a circular cup deep drawing test to measure the formability of the multilayered sheet. A maximum value for the LDR of about 2 was achieved at $250^{\circ}C$, which is the appropriate forming temperature for the Mg alloy. Fracture patterns on a circular cup and thickness of formed part were predicted by a rigid-viscoplastic FEM analysis. Two kinds of modeling techniques were used to simulate deep drawing process of multilayered sheet. A single-layer FE-model, which combines the three different layers into a macroscopic single layer, predicted well the thickness distribution of the drawn cup. In contrast, the location and the time of fracture were estimated better with a multi-layer FE model, which used different material properties for each of the three layers.

• Transactions of Materials Processing
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• v.24 no.4
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• pp.248-255
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• 2015

The warm drawing of magnesium alloy AZ31B sheet is affected by temperature because tensile elongation is changed due to the elevated temperature. In the current study, the effect of temperature was investigated for an automotive dash panel part by both experimental and FE analysis. Tensile tests were performed to obtain mechanical properties for various temperatures. AZ31B alloy sheet shows increased total elongation with increasing deformation temperature in the range of 200 to 300℃. The heating channel inserted into the die was used to regulate and to obtain an optimal temperature. A temperature controller was constructed to reduce temperature variation. Warm drawing of magnesium alloy AZ31B was performed to produce the desired shape of the lightweight automotive dash panel. The simulated results showed good agreement with the experimental results.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.351-356
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• 2014

The current study aims to predict the forming limits considering the deformation characteristics of tailor rolled blank(TRB) during hot stamping. The formability of TRB is affected by the TRB line orientation because elongations change due to the intrinsic geometry within the sheet. To evaluate the forming limits, Nakazima tests were conducted at elevated temperatures with different TRB line orientations. Forming limit diagrams(FLD) of TRB can be predicted by an interpolating equation based on the Nakazima test. Predicted FLDs were used in FE-simulations of a rectangular drawing. The predicted limit drawing height was compared with experimental results. The simulation results show good agreement with the experimental ones with an error range of 3%.