• Transactions of Materials Processing
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• v.31 no.2
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• pp.51-56
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• 2022

In this study, finite element analyses were performed by applying a stress ring and split die design to relieve the tensile stress acting on the die due to high surface pressure during warm-closed forging. The applied material was a yield-ratio-control-steel (YRCS). It was used without quenching or tempering after forging. In the case of stress rings design, the number of stress rings and the tolerance for shrink fit were different. Vertical and horizontal splits were applied for insert die split design. Case 5 die with three stress rings, 0.2 % shrink fit tolerance, and vertical split was selected as an effective die design for tensile stress reduction. Based on die stress reduction analyses, Case 5 die for warm-closed forging was produced and smooth forgeability was secured, making it possible to manufacture forging product of yoke with the required geometry. In addition, controlled cooling using warm forging heat was applied to secure mechanical properties of yokes. When oil cooling was used for direct controlled cooling after warm-closed forging, a relatively uniform Rockwell hardness distribution and high mechanical properties could be obtained.

• Journal of Powder Materials
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• v.4 no.4
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• pp.258-267
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• 1997

The powder forging process is an attractive manufacturing route for bevel gears. It offers beneficial material utilization and the minimization of finishing operations over that of conventional hot forging. The paper describes the process conditions for the powder forging of bevel gear, for example, powder alloy design, preform design, deformation of sintered preform, forging processes. The characteristics of prototype gear are investigated with microstructure, the density distribution, surface roughness of tooth, bending strength test of tooth, etc. The results of the bending strength test may prove the mechanical properties of powder forged gear.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.291-296
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• 2000

The sensitivity method has been applied to find perform shape that results in the desired shape after forging. As a basic example, initial shape of specimen for the cylinder shape without barrelling after forging has been found. The method is then applied to various shapes of 3D free forging and initial shapes of the corresponding specimens after forging have been found successfully. The sensitivity method is proven to be an effective and accurate tool for the preform design.

• Transactions of Materials Processing
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• v.14 no.2 s.74
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• pp.126-132
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• 2005

The isothermal forging design of a Ti-6Al-4V wing shape was performed by 3D FE simulation. The design focuses on near-net shape forming by the single stage. The process variables such as the die design, pre-form shape and size, ram speed and forging temperature were investigated. The main design priorities were to minimize forging loads and to distribute strain uniformly in a given forging condition. The FE simulation results for the final process design were compared with the isothermal forging tests. The instability of deformation was evaluated using a processing map based on the dynamic materials model(DMM), including flow stability criteria. Finally, a modified process design for producing a uniform Ti-6Al-4V wing product without forming defects was suggested.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.7-15
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• 1998

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The program consists of forward and backward tracing processes. In the forward program, flash, die filling and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet in conventional forging are determined from the final-shape data based on flash design. And the analysis is described for merit of flashless precision forging. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of forging load and flow pattern are in good agreement with the experimental results.

• Transactions of Materials Processing
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• v.10 no.4
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• pp.294-301
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• 2001

The sensitivity method has been applied to find perform shape that results in the desired shape after foring. As a 2D example, initial shape of specimen for the cylinder shape without barrelling after forging has been found. The method is then applied to various shapes of 3D free forging and initial shapes of the corresponding specimens after forging have been found successfully The sensitivity method is proven to be an effective and accurate tool for the preform design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.06a
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• pp.188-194
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• 1995

In this paper, several application examples of a forging simulator POSFORM were introduced with some forged parts for verification purpose, found in cold or hot forging companies. the forging simulator was also introduced in brief. The simulated results and the actually forged ones were compared in shape or metal flow. It has been shown that the design approach based on the forging simulator is most efficient in reducing design tryouts and development cost and accumulating design experience and technology effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.19-22
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• 2003

In this study, the design of prestressed die for spur gear forging have been investigated. The stress concentration at notch of the die insert is very important in the design of die for the forging of spur gear such as non-axisymmetric geometry. In the previous study, the flexible tolerance method was used in order to search the optimal value of design variables considering the constrain conditions. In the design process, it was also involved the safety factor to the yield strength of each ring by considering allowable tensile or compressive hoop stress in each ring. Using this technique, the die deign for spur gear forging has been successfully performed without yielding of the die after shrink fitting and during forging.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.1
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• pp.120-126
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• 2002

The near net shape forging of gears offers significant technical and economic advantages ever other forms of manufacture. These potential benefits can however only be realized by careful die design. This paper describes a computer-based methodology fur achieving this. A Visual-BASIC program has been developed on a rule based system that enables optimal design of the dies taking into account the elastic deflections generated in shrink-fitting the die inserts and that caused by the stresses generated in the forging process. The method also enables the profile of the spark erosion electrode to be determined. An example of the application to forging spur gears is given.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.127-132
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• 2003

This article mainly introduces the research of closed forging on 20MN hot die forging presses. After transforming of the equipments, optimizing of die design and improving of die-manufacturing precision, gear blanks used in car gearbox have been forged out without fins successfully.