• Journal of the Korean Society of Mechanical Technology
• /
• v.13 no.1
• /
• pp.105-112
• /
• 2011

Increasing needs for light weight and high safety in modern automobiles induced the wide application of high strength steels in automotive body structures- The main difficulty in the forming of sheet metal parts with high strength steel is the large amount of springback including sidewall curl and twist in channel shaped member parts- Among these shape defects, twist occurs frequently and requires numerous reworks on the dies to compensate the shape deviation- But until now, it seems to be no effective method to reduce the twist in the forming processes- In this study, a new forming process to reduce the twist deformation during the forming of automotive structural member was suggested- This method consists of forming and restriking of embosses on the sidewall around the stretch flanging area of the part- and was applied in the forming process design of an automotive front side inner member with high strength steel- To evaluate the effectiveness of the method, springback analysis using $Pamstampa^{tm}$ was done- Through the analysis results, the suggested method was proven to be effective in twist reduction of channel shaped parts with stretch flanging area.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.4
• /
• pp.16-22
• /
• 2005

The flow forming has been used to produce long thin walled tube parts, with reduced forming force and enhanced mechanical and surface quality for a good finished part, compared with other method formed parts. So flow forming technique is used widely in industrial production. Especially spinning and flow forming techniques are used frequently in automotive, aerial, defense industry. In this paper, finite element method analysis of three-roller backward flow forming of a workpiece is carried out to study effects of forming depth and feed rate on forming force. The axial and radial forces on several forming depth and feed rate conditions are obtained.

• Design & Manufacturing
• /
• v.6 no.1
• /
• pp.63-66
• /
• 2012

In the manufacturing of a LCD TV bottom chassis, the distortion after forming should be suppressed below pre-defined amount to avoid contact with electric components. Finite element analysis procedure of forming and springback of a LCD TV bottom chassis is developed to investigate the distortion behaviour. It is shown that after the first forming large distortion occur due to uneven metal flow induced by various embossings. In the second forming, distortion is decreased by introducing bead that absorbs the excessive metal flow. It is proved that analysis method could describe these behaviour effectively. The developed analysis method can be used to find the proper location and shape of bead more quickly and effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.10a
• /
• pp.175-179
• /
• 2004

Since the formability of AZ31 magnesium alloy is not good in room temperature, it is known that high temperature forming is advantageous. However, many studies are necessary to find the proper forming temperature for Mg alloy. In this study, experimental and FEM analysis are performed to investigate the forming temperature for AZ31 sheet. The deep drawing process of square cup is used in forming experiment and FEA. The investigations are performed in three forming temperature, room temperature, $250^{\circ}C\;and\;400^{\circ}C$. The square cup is well formed in $250^{\circ}C$ forming temperature, on the other hand, the crack and failure is presented in corner section in room and $250^{\circ}C$ forming temperature. The main cause is investigated as the effect of hardening range by the experimental and FEM results.

• Transactions of Materials Processing
• /
• v.9 no.1
• /
• pp.35-42
• /
• 2000

In this paper, we developed the hydroforming simulator which can apply an axial compressive force and high internal pressure to bulge a tube. Experimental dtudies have been performed to investigate the effect of each parameters such as internal pressure and axial compression stroke required for the forming of circular components. Under the improper forming conditions there were two forming failures. One was the axial buckling due to excessive axial compressive load and the other was the circumferential necking fracture due to relatively high internal pressure. A safe forming zone without any failures exists between these two extreme zones. Also the condition of forming failure such as fracture is examined throughout the theoretical analysis. This paper covers a brief overview of the mechanism of hydroforming process as well as the design of die and tools.

• Transactions of Materials Processing
• /
• v.15 no.6 s.87
• /
• pp.467-472
• /
• 2006

The forming limit diagram of tube is required for the part design and the formability analysis of tube hydroforming. The finite element analyses of simple bulge test were done to obtain the various strain combinations on FLC. The finite element analysis results were shown that the bursting at various strain combinations could be induced by simple bulge test. The experiment oi tube bulge test was carried out according to the test condition that obtained from finite element analysis and the left hand side of forming limit diagram was built.

• Transactions of Materials Processing
• /
• v.10 no.1
• /
• pp.23-29
• /
• 2001

In this study, the optimized initial hole shape for T-branch forming was proposed to obtain effective welding region. Design variables were determined by approximation analysis using volume constant condition. We performed 3D elastic-plastic FEM(Finite Element Method) analysis to simulate T-branch forming process. The variation of height and thickness of T-branch with various hole shapes was investigated. The optimized initial hole shape equation was obtained by using results for the numerical analysis.

• Transactions of Materials Processing
• /
• v.18 no.7
• /
• pp.556-564
• /
• 2009

Flexible forming process for sheet material using reconfigurable die is introduced based on numerical simulation. In general, this flexible forming process using the reconfigurable die has been utilized for manufacturing of curved thick plates used for hull structures, architectural structures and so on. In this study, numerical simulation of sheet metal forming process is carried out by using flexible dies model instead of conventional matched die set. The numerical simulation and experimental verification for sheet metal forming process using a flexible forming machine that is more suitable for thick plate forming process are carried out to confirm the appropriateness of the simulation process. As an elastic cushion, urethane pads are utilized using hyperelastic material model in the simulation for smoothing the forming surface which is discrete due to characteristics of the flexile die. In the flexible forming process for sheet metal, effect of a blank holder is also investigated according to blank holding methods. Formability in view of occurrence of dimples is compared with regard to the various punch sizes. Consequently, it is confirmed that the flexible forming for sheet material using urethane pad has enough capability and feasibility for manufacturing of smoothly curved surface instead of conventional die forming method.

• Transactions of Materials Processing
• /
• v.9 no.6
• /
• pp.670-680
• /
• 2000

The purpose of this study is to provide the database of forming limit diagram applicable to the warm forming of oil pan. The test materials are SCP1 and SCP3C with the thickness of 1.4mm which is used for the oil pan of automobile. The testing temperature is 5$^{\circ}C$~15$0^{\circ}C$ which is In the range of practical usage. The results are the forming limit diagram limiting dome height and the maximum punch load at each temperature such as 5$^{\circ}C$, $25^{\circ}C$, 6$0^{\circ}C$, 9$0^{\circ}C$, 12$0^{\circ}C$ and 15$0^{\circ}C$. From these results, we can see that the forming limit curves are translated depending upon the temperature and that FLC at low temperature is higher than at high temperature. Both of limiting dome height and maximum punch load also decrease as the temperature increases. Present results can be useful for die trial and forming analysis as a tool of evaluating the forming severity for the sheet metal forming processes at the warm working condition by comparing the practical strains with FLC.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.218-221
• /
• 2008

Hot Press Forming (HPF), an advanced sheet forming method in which a high strength part can be produced by forming at high temperature and rapid cooling in dies, is one of the most successful forming process in producing components with complex geometric shape, high strength and a minimum of springback. In order to obtain effectively and accurately numerical finite element simulations of the actual HPF process, the flow stress of a boron steel in the austenitic state at elevated temperatures has been investigated with Gleeble system. To evaluate the formability of the thermo- mechanical material characteristics in the HPF process, the FLDo defined at the lowest point in the forming limit diagrams of a boron steel has been investigated. In addition, the simulation results of thermo-mechanical coupled analysis of an automobile one-piece lower-arm part are compared with the experimental ones to confirm the validity of the proposed simulations.