• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2749-2761
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing. Finite element results by using the proposed model also well predicted experimental data in the literature for densification behavior of nanocrystalline zirconia powder during pressureless sintering and sinter forging.

• Transactions of Materials Processing
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• v.12 no.6
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• pp.536-541
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• 2003

In this paper, the rigid-viscoplastic finite element method is employed together with an iteratively force-balancing method to analyze a piercing and trimming process with a spring-attached die in hot former forging. An actual piercing and trimming process with a spring-attached die is investigated in detail and a generalized analysis model is proposed. A multi-stage hot former forging process is simulated under various spring constants. The analyzed results are discussed in order to investigate the effects of spring constants on the metal flow lines and the formed shapes. Then an optimal piercing and trimming process in hot former forging is devised.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1570-1575
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• 2007

The cold-forging process analysed in this paper deals with the cam bolt of a nonaxisymmetric shape which mainly is used as a part in the steering system of a vehicle for the purpose of adjusting shock absorb. So both strength and endurance are very important for the cam bolt. In this study, cam bolt forging process is composed of four stage processes. For three forging stages, shape of workpiece will be eccentrical. And then bolt head and washer of eccentrical shape is created in last stage. 3D finite element analysis repeatedly has been performed with changing dimension of die to obtain adequate former multi forging process and die shape. Simulation results reviewed have influence on deciding design of die and forging process. As a result, Simulation results have provided a direction to improve the process.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.313-318
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• 1999

Many products related to automobile and airplane industry have been manufactured by semi-solid forging. In this paper finite element analysis of product by combined extrusion in semi-solid state was performed and its experimental verification using A356 was conducted. distribution of solid fraction was analyzed and compared with the experimental microstructure in the product. In addition, distribution of temperature in the product was analysed by finite element method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.546-550
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• 1996

A fully automatic computer simulation technique of axisymmetric multi-stage compound forging processes was presented in this paper. A penalty rigid-viscoplastic finite element method was employed together with an improved looping method for automatically remeshing with quadrilateral finite-elements only. An application example of six-stage axisymmetric forging processes involving one cold and two hot forging processes, two piercing processes and a sizing process was given with emphasis on automatically tracing the metal flow lines through the whole simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.99-102
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• 2005

An approach to adaptive finite element analysis of three-dimensional forging processes is presented in this paper. In the approach, an optimal tetrahedral element generation technique is employed and the mesh density is specified by the combination of the normalized effective strain and the normalized effective strain rate. The approach is applied to computer simulation of an enclosed die forging process of a bevel gear and its results are compared with experiments.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.37-43
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• 2006

In this paper, an approach to adaptive finite element analysis of three-dimensional forging processes is presented with emphasis on remeshing. In the approach, an optimal tetrahedral element generation technique is employed and the mesh density is specified by the combination of the weighted normalized effective strain and the normalized effective strain rate as well as the weighted normalized curvature. The approach is applied to computer simulation of an enclosed die forging process of a bevel gear and its results are compared with its related experiments. It has been shown that the analyzed results are in good agreement with the experimental ones.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.49-54
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• 2002

The Finite Element Method is applied to the determination of the deformed bulge profile and strain distribution during upset forming of cylindrical billets. From the results of simulation, the bulging along the z-axis becomes more severe with increasing eight reduction, and with increasing friction at the die-material interface. The present method can be used for the simple prediction of the deformed shape and strain distribution in upset forging of cylindrical billets with dissimilar fictional conditions at the die-material interfaces.

• Transactions of Materials Processing
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• v.30 no.1
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• pp.35-42
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• 2021

Magnesium alloys are used in electronic devices such as laptops due to their lightweight features as well as vibration absorption and electromagnetic shielding properties. However, the precision of electronics is limited by the large number of small and precise ribs, the cost-effective manufacture of which requires appropriate technology. Plate forging is an efficient manufacturing process that can address these challenges. In this study, plate forging of magnesium alloys was investigated specifically for the fabrication of laptop cover. The plate forging process with back-pressure was used for near-net shape formation. Finite element analysis was used to select appropriate variables for back-pressure formation to generate ribs of various sizes and shapes without defects. The reliability of the analysis was verified to manufacture the prototype. The effect of back-pressure can be verified via fabrication of prototypes as well as structure and forming analysis based on finite element method. The process design factor of back-pressure increases formability without defects of under-filling and flow-through. Moreover, the tensile strength was maintained even after high temperature plate forging at 370 ℃, and the elongation was improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.120-123
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• 1999

The precision cold forging process for steering yoke of automobile has been analysed by using rigid-plastic finite element analysis code DEFORM-3D Also the experiment has been performed through the optimized process. Until now steering yoke has been largely manufactured by hot forging or welding of forged head and shaft parts because of technical difficulty. the study has shown successful results of the precision cold forging through the proper selection of the process.