• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.149-152
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• 2000

By using a three-dimensional finite element program HydroFORM-3D based on a rigid-plastic model, the hydroforming process for automobile subfrmae is analyzed in this study. The goal of this study is to accomplish preform design and determine the level of internal pressure for producing final hydroformed subframe component. Prior to hydroforming, the initial tube blank must be bent to the approximate centerline of the final part to enable the tube to be placed in the die cavity, After then, a preforming operation like stamping is carried out to the prebent tube. Finally, hydroforming process is performed to the preformed tube to get the final production. And through ductile fracture theory, the failure, bursting, is predicted during hydroforming process for tube blank with different diameter.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.190-193
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• 2004

Ever since the ideal forming theory has been developed fur process design purposes, application has been limited to sheet forming and, for bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was performed under the plane-strain condition based on the theory previously developed. In the ideal flow, material elements deform following the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-strain flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, for a prescribed final part shape, schemes to optimize a preform shape out of a class of initial configurations and also to define the evolution of shapes and boundary tractions were developed. Discussions include the two problematic issues on internal tractions and the non-monotonous straining. For demonstration purposes, numerical calculations were made for a bulk part under forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.36-39
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• 2003

Due to the strength and biocompatibility requirement, the stainless steel SUS 316L is widely used for trauma internal fixation device. SUS 316L can be hardened and strengthened only by cold work. In this work, the material compression test is performed both in laboratory and computer simulation by a FEM analysis software DEFORM to correlate the hardness to strain. This data is then used for preform design and predict the hardness of the finish bone plate forging. Finally, we compared the hardness between the actual forging and computer analysis results. Although the predicted hardness from computer simulation. is 55HV higher than the final forging sample, we can get good compatibility on the hardening tendency of cold forging.

• Transactions of Materials Processing
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• v.10 no.6
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• pp.478-484
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• 2001

Tube Process (TP) is a process to produce permanent magnets using a deformable tube for densification of magnet powder. This process claims that it can accomplish both densification and anisotropication in one step forming. This process is distinguished from other processes since it uses a deformable copper tube for densification of magnet powder. In this paper, simulation has been carried out for tile Tube Process in a closed die considering the compressibility of powdered material, arbitrary curved shape and deformable body contact between Nd-Fe-B magnet powder and a copper tube. Results show that the finite element analysis of the Tube Process plays an important role in the stage of preform design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.369-372
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• 2006

Monolithic forging of cask is required continuously. Body-base monolithic forging of cask has advantage of an economical manufacturing process and better reliability for nuclear applications. Through the finite element analysis and parametric study of design variables, those are die angle, groove length and flange thickness, the optimal dimensions of preform and die sets are determined in order to develop a suitable forging process for body-base monolithic forging. To verify the result of finite element analysis, the physical model of 1/30 scale of actual product using plasticine was carried out. The result of this experiment, deformed shapes were very similar to the finite element analysis. As a result of this work, the special piercing method was developed using blank material consisting of a flange, groove and squared part.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.395-403
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• 2007

Railroad track consists of relatively simple structures such as rail, sleeper, ballast. Roadbed shares vertical pressure by train load which passed through rail to ballast as base that supports the track. For evaluating stress and displacement of roadbed due to the railroad load is an important role on the track as a basic data for estimation of the durability and design of the roadbed thickness. GEOTRACK program applied multi-layered theory was developed for analyzing railroad track structure. GEOTRACK program is a sort of numerical analysis program which has advantage that can analysis component of track by simple method. In this study, this program was used to preform the numerical analysis by changing track conditions and roadbed conditions such as tie, reinforced roadbed, dynamic wheel load, Resilient modulus and so on. Further detail will be presented on the paper.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.125-130
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• 1999

In order to reduce the forming load of backward extrusion to a feasible level a new backward extrusion processes are proposed. In these process the shape of punch and die for conventional backward extrusion are change to open backward extrusion. To analyse the process numerical simulations by the finite element method has been performed, This simulation gave good results concerning the prediction of the forming load material flow and the corresponding shape of forged products, . These predictions set the limits of the preform shape and forming load depending on the punch and die geometry. The results show that the forming load is reduced significantly when the conventional backward extrusion change to open backward extrusion.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.82-85
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• 1999

Permanent magnets of Nd-Fe-B group have kept a key post in the permanent magnet market and used in various parts. Tube Process is a process to produce permanent magnets using a deformable tube for denslfication of powder magnets. Advantage claimed for this process is that it can accomplish both densification and anisotropication in one step forming. In this paper. the simulation has been carried out for a full Tube Process in a closed Qe considering the compressibility of material, arbitrary curved shape and deformable body contact between Nd-Fe-B powder magnet and copper tube. The results show that the analysis of Tube Process is applicable with great help in the stage of preform design.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.267-281
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• 1995

Preform design is one of the critical fields in metal forming. The finite element method(FEM) has been effective in designing preforms and process sequence, for which the backward tracing scheme of the rigid-plastic FEM has been explored. In this work a program using the backward tracing scheme by the rigid-plastic FEM is developed for three-dimensional plastic deformation, which is an extension of the scheme from two-dimensional cases. The calculation of friction between workpiece and die, and handling of boundary conditions during backward tracing require sophisticated treatment. The developed program is applied to upsetting of a rectangular block and to side pressing of a cylindrical workpiece. The results of the two applications show feasibility of the program on three-dimensional plastic deformation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.251-251
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• 2004

이 연구에서는 주단조 공정을 자동차 부품인 low control arm 제조에 적용하였다. Al6061에 주단조 공정을 적용함므로써 재료비 감소와 기존의 스틸제품보다 경량화 효과를 얻을 수 있다는 것을 증명하기 위함이다. 첫째로 단조 재료인 A16061의 최적 주조조건을 찾기 위하여, 주조 실험은 알루미늄의 주입온도, 금형온도, 주입시간을 조절함으로써 수행되어졌다. 최적주조조건은 주입온도 $700^{\circ}C$, 금형온도 30$0^{\circ}C$, 주입시간 10초로 정하여졌다. 각각의 미세조직을 관찰하고 응력-변형률곡선을 구하기 위하여 열가단조실험은 빌렛온도, 변형률속도와 감소율을 기초로 하여 수행되어졌다.(중략)