• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.184-187
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• 2005

Forging process is one of the forming process and is used widely in automobile parts and manufacture industry. Especially the gears like spur gear, helical gear, bevel gear were produced by machine tool, but recently they have been manufactured by forging process. The goal of this study is to study forming process with data obtained by comparison between forward extrusion and upsetting simulation results and formability improvement by various heat treatment conditions. By analysis data of 3D FEM by upsetting and forward extrusion forming, the forming process of clutch gear develops using data based on 3D FEM analysis. Through tensile test using specimens by various heat treatment conditions, the optimal heat treatment condition is obtained by comparison the results of tensile test.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.531-534
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• 2008

A new forming process of the large-size forging within the limit of forming loads is developed by introducing the drawing process, which usually used to apply to sheet forming. For the development of the forming process, corresponding numerical simulation are carried out. The approach is based on the Taguchi method, and utilize the DOE for design of FEM analyses. In this study, the important factors are chosen at first, and then the concept of signal-to-nose(S/N) rate is applied to evaluate the formability of large size forging-products, and each value of the design parameter is determined.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.122-132
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• 1999

This study describes a dynamic model of the hydroforming process which is used for precision forming of sheet metals. To help the controller design for the control of the forming pressure needed for this process as well as to investigate the effect of system parameters on the dynamic behavior, dynamic modeling is performed with emphasis on hydraulic servo system which actuates the forming machine. Since the model contains several unknown parameters, these were estimated via a least square parameter identification method. Based upon the identified model, a series of simulations were performed for various operating conditions. The results were compared with those of the experiments to verify the validity of the proposed model. The comparison study shows that the proposed dynamic model can describe dynamic behavior of the forming pressure of the hydroforming process to desirable accuracy.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1685-1696
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• 1994

In this paper, a new forming process of the large-size forgings within the limit of forming loads is developed by introducing the incremental forging method and combined forming method. For the development of the forming process, various related processes are proposed and modelling experiments of plasticine and corresponding numerical simulation ate carried out. Thus, an optimal process considering the productivity and economical efficiency is recommended from the study of formability and forming loads, etc. The selected process is subjected to a modelling experiment of lead and 1/7 scale prototype experiment of the real material so as to verify the effectiveness of a selected process as well as to determine the design parameters. The developed process is then applied the forging product of dome shape. Dome-shaped forgings can be produced by the developed process within the limit loads and with the simple tools.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.89-96
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• 2009

In recent years, there has been a considerable interest in the application of super plastic forming in the aircraft and automotive industries. This requires a detailed design of the technological process in order to exploit its peculiar potentialities better. Nowadays, the finite element method is used to plan the sheet metal forming processes whose simulation requires determination of material constants for super plastic materials. The present work is aimed to show a simple method to characterize super plastic materials duplex stainless steel which was formed by a constant gaspressure to hemispheres with and without back pressure. The forming operation was performed using an in-house designed and built biaxial forming apparatus. The temporal change of dome heights of hemispheres were measured for applying the pressures. The flow stresses and strain rates developed at the top of the dome during the forming step were shown to follow closely the flow stress - strain rate relationship obtained from the strain rate change tests performed at the same temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.06a
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• pp.147-162
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• 1994

Generally, the forming process of sheet metal is very complex and difficult process because of many variables such as tool geometry, material properties and lubrication. In this view point, the numerical analysis of sheet metal forming process is very difficult. High speed computer is used to model complex sheet metal forming process on a reasonable time scale. The design and development of sheet metal parts in the automotive industry and the need for improved sheet forming process and reduced part development cost have led to the use of computer simulation in tool/die design of sheet metal pressing. HMC(Hyundai Mator Company) has invested to develop programs for analysis of sheet metal forming process with connection of Universities. As a result, several programs were developed. Recently, the commercial software, PAM-STAMP of ESI was installed and is being tried to application of it to the real automotive panels. This article reviews the ongoing activities on development and application of analytical modeling of sheet metal forming at HMC.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.310-313
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• 2007

In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. In this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal roll flower model and proper roll-pass sequence can be suggested by analyzing courcenter strain and longitudinal strain according to the roll-pass with FEM simulation. And also effects of the process parameters on the final shape formed by roll forming defects a evaluated.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.393-400
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• 2008

Springback is one of the most difficult phenomena to analyze and control in sheet forming. Most of traditional springback control methods rely on experiences of skilled workers in industrial fields. This study focuses on prediction and generation of optimum reconfigurable die surfaces to control shape errors originated by springback. For this purpose, a deformation transfer function(DTF) was combined with finite element analysis of the springback in the 2D sheet forming model of elastic-perfectly plastic materials under the condition without blank holder. The results showed shape errors within 1% of the objective shape, which were comparable with analytically predicted errors. In addition to this theoretical analysis, DTF method was also applied to 2D and 3D sheet forming experiments. The experimental results showed ${\pm}0.5$ mm and ${\pm}1.0$ mm shape error distribution respectively, demonstrating that reconfigurable die surfaces were predicted well by the DTF method. Irrespective of material properties and sheet thickness, the DTF method was applicable not only to FEM simulation but also to 2D and 3D elasto-reconfigurable die forming. Consequently, this study shows that springback can be controlled effectively in the elasto-RDF system by using the DTF method.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.141-148
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• 2017

A process comprising a hot extrusion process and a warm forging process was designed to form a T-shaped aluminum structural component with a high degree of difficulty by the plastic forming method. A circular cylindrical part was extruded with a hot extrusion process, and then an embossing part was formed with a warm forging process. The formability and the maximum load required for forming were then determined using a forming analysis program. The hot extrusion process was executed at $450^{\circ}C$ under the extrusion speed at 6 mm/s, while the warm forging process was executed at $260^{\circ}C$ under the forging speed at 150 mm/s. For both the processes, a condition by which friction would not be generated between the mold and the material was implemented. The analysis results showed that the load required for hot extrusion was 1,019 tons, while the load required for the warm forging was 534 tons. The T-shaped part was manufactured by using a 1,600 tons capacity press. The graphite lubricant was coated on the mold as well as the material. A forming experiment was performed under the same condition with the analysis condition. The measured values from the load cell were 1,210 tons in the hot extrusion process and 600 tons in the warm forging process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.51-59
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• 2019

Flow forming is an eco-friendly and high-efficiency plastic deformation process with fewer chips during a process which is specifically used to manufacture seamless tubular products like tire wheels, rocket motor cases etc. On the development of mortar barrel using Inconel718 tube, some flow formed products had dimensional errors on their thickness. In this study, our purpose is to optimize the process conditions with the smallest dimensional error. In order to find an optimum process condition, 2D axisymmetric FEM simulation analyses with Taguchi method were conducted. Geometric variables (attack angle, flatting angle, roller nose radius) and operating parameters (depth of forming, feed rate) are considered as control factors. Forward flow forming with single roller was first analyzed to determine the effective factors using AFDEX software and attack angle of the roller was identified as the most influential factor. Also, the nose radius of the rollers was confirmed as a significant factor in multi-rollers flow forming system. The effect of rollers offset values are also studied and finally, we proposed optimal conditions to improve the accuracy of flow forming process with Inconel718 tube for mortar barrel manufacturing.