• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.152-158
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• 2006

The AutoForm previously used the membrane element and it accomplished sheet metal forming analysis. The membrane analysis has been widely applied to various sheet metal forming processes because of its time effectiveness. However, it is well-known that the membrane analysis can not provide correct information for the processes which have considerable bending effects. In this research experimental results were compared with the analysis results obtained by using the shell element which is applied newly in the AutoForm commercial software. The shell element is a compromise element between continuum element and membrane element. The Finite element method by using shell element is the most efficient numerical method. From this research, it is known that FEA by using shell element can predict accurately the problems happened in actual experimental auto-body panel.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.144-147
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• 2002

In this study, springback analysis of side rear member is carried out. Side rear member is one of the parts which shows severe springback problems. Forming, trimming, flanging and springback stages can be analyzed successively. From forming analysis, we identified the possible spots in which tearing may occur and can prevent failure. In springback analysis we used the boundary conditions same as applied to the blank on the checker so that the computational result can be compared with experimental one. Form .the comparison, springback analysis can yield relatively good results in a qualitative sense. However, in order to get good deformation result quantitatively, there still remains unsettled tasks in the forming analysis with very small die radius. It is found that we have to develop the element with better bending characteristics and precise contact treatment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.82-85
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• 2005

In order to see the effect of die deformation on the forming of sheet metal, the draw-ins, strains, and springbacks of an automotive fender panels are numerically simulated considering the die deformation found by the simultaneous structural analysis of press and dies. The comparison of the forming analysis result between the rigid die and the deformed die layout shows that the deformed tool provides more accurate forming and springback result.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.501-506
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• 2008

In this study, a forming magnesium alloy circular cup was simulated accounting for heat transfer at elevated temperatures. In order to predict the failure of magnesium alloy sheet during simulation, the forming limit diagram, which is used in sheet metal forming analysis to determine the criterion for failure, was investigated. For the failure prediction in the simulation accounting for heat transfer, the forming limit diagram for a temperature the same as the temperature of the blank element was used. The result of the simulation showed that the drawn depth increases with the increase of the die-holder temperature, and is in accord with the experimental results above the die-holder temperature of $150^{\circ}C$. The forming limit diagram provided a good guide for the failure prediction of warm forming simulation accounting for heat transfer. In addition, the effect of the tool shoulder radius on the drawn depth at various tool temperatures is verified using the simulation conditions which agreed with the experimental results.

• Transactions of Materials Processing
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• v.27 no.4
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• pp.236-243
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• 2018

A multi-point forming die (MPFD), which has been used for producing curved plates, is capable of forming various curved plates with just one MPFD. However, in real industries, an MPFD is difficult to be adopted since the structural properties, punch strength, elastic recovery correction and dimensional accuracy become problems. In order to overcome these problems, the hot multi-point forming die (HMPFD) was proposed in this study. This HMPFD commonly provide more less spring-back and forming load than conventional MPFD. Nevertheless, this process is very difficult to form the curved plate, because the final curved shape of the plate depends on many process variables such as the punch/nozzle arrangement (height and distance), the radius of punch, contact conditions between plate and punch. In this study, the forming characteristics of HMPFD and conventional MPFD are compared with each other through the finite element analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.52-58
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• 2014

This study consists of two parts. The first discusses the development of a single production forming machine which was reported in earlier papers. The second outlines the development of a multi-production forming machine, which consists primarily of a film feeding unit, an unwinding unit, and a heating block unit. The heating block unit of the multi-production forming machine has 30 members per die. An analysis of the stress deformation and temperature deviation of this machine is carried out using ANSYS Workbench and CFX-11 under the design conditions. According to this analysis, the maximum deflection in the Z-direction is $0.05104{\mu}m$ and the maximum temperature deviation is $0.7^{\circ}C$ when the temperature of the heating block unit is $175^{\circ}C$. It was also found that these values are structurally safe. The advantage of the developed multi-production forming machine is demonstrated to be in its offering of a proper voice test.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.236-244
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• 2009

In response to growing environmental and collision-safety concerns, the automotive industry has gradually used high-strength and ultla-high-strength steels to reduce the weight of automobiles. In order to overcome inherent process disadvantages of these materials such as poor formability and high springback at room temperature, hot forming has recently been developed and adopted to produce some important structural parts in automobiles. This method enables manufacturing of components with complex geometric shapes with minimal springback. In addition, a quenching process may enhance the material strength by more than two times. This paper investigates mechanical and forming characteristics of high-strength boron-alloyed steel with hot forming, in terms of hardness, microstructure, residual stress, and springback. In order to compare with experimental results, a finite element analysis of hot forming process coupled with phase transformation and heat transfer was carried out using DEFORM-3D V6.1 and also, to predict high temperature mechanical properties and flow curves for different phases, a material properties modeler, JMatPro was used.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.253-257
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• 2005

A tube hydroformability testing system was designed and fabricated so as to observe the forming process and to apply forming condition along arbitrarily pre-programmed internal pressure-axial feed path. The forming limit diagram of A6063 extruded tube, of 40.6 mm outer diameter and 2.25 mm thickness, was successfully obtained through free bulging and T-forming tests except the region of high positive minor strain. It is found that the data points marked on the FLD are mostly located near the strain paths from the finite element analysis excluding the cases of large axial feed. There exist data points even in the area beyond the uniaxial tension mode, since the reduction in thickness decreases due to the axial feed. The forming limit from T-forming test was considerably lower than that from free bulge test. It seems because the deformation is localized at the pole.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.105-112
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• 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
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• v.9 no.4
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• pp.16-22
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• 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.