• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.124-130
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• 2008

The effect of nitrogen gas pressure in arc ion plating on surface properties of the TiN-coated high speed steel(SKH51) is presented in this paper. The surface roughness, micro-particle, micro-hardness, coated thickness, atomic distribution of TiN, and adhesion strength are measured fur various nitrogen gas pressures. It has been shown that the nitrogen gas pressure has a considerable effect on the surface roughness, adhesion strength, atomic distribution of TiN, and surface deposition of TiN of the high speed steels but that it has little influence on the micro-hardness and coated thickness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.441-444
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• 2009

In this research, a hot and cold combined forging process for manufacturing net-shape one-way clutch bearing outer race of an automobile automatic transmission unit is developed. The process is composed of hot forging for manufacturing an optimized gear-like perform and precision cold forging for sizing the perform into final net-shape product. Finite element simulation techniques are applied to find the optimized process designs including blank and die shapes. The predictions and experiments are compared, revealing that they are in good agreement with each other. The dimensional test showed that the important dimensional requirements on gear tooth-like shape of the forged product were fulfilled.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.437-440
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• 2009

In this paper, an aluminum ring forging process of manufacturing an optimized perform for a hot forging process is simulated using AFDEX 3D, a general-purpose metal forming simulator based on rigid-thermoviscoplastic finite element method. Non-isothermal analysis is carried out and the predictions are compared with the experiments in terms of dimensional accuracy. It was shown that the predictions are in good agreement with the experiments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.44-47
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• 2009

In this paper, limitation of rigid-plastic finite element method caused from rigid-plasticity assumption and numerical problem is investigated in detail and a useful scheme is proposed to get rid of the plastic deformation in rigid or elastic region. A typical example of a possible long bar extrusion process is given, which may be impossible to simulate without using the proposed scheme. The scheme is successfully applied to simulating the long bolt forging processes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.177-182
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• 2007

We simulated an electric upsetting process by the rigid-thermoviscoplastic finite element method. Several engineering assumptions were made to calculate the heat generation due to the electric resistance. The skin effect of the bar was taken into account for the heat generation. The approach was applied to simulate an artificial electric upsetting process for the exhaust valve of the ship engine.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.183-188
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• 2007

We simulated a hot forging process for the spider with four legs and an enclosed die forging process for the spider with three legs using an intelligent forging simulator AFDEX 3D and compared the predictions with the experiments in terms of the deformed shape. The formation of characteristic lines was emphasized in the simulation to simulate the extruded legs with higher accuracy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.195-200
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• 2007

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.201-206
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• 2007

In this paper, we apply a three-dimensional rigid-plastic finite element method to simulate an unsteady-state roll forming process. A typical roll forming process is investigated from the standpoint of computer simulation and its realistic analysis model is proposed. The material is considered as bulk material and discretized into hexahedral finite elements. The presented approach is applied to simulating the roll forming process of straight stringer used for aircraft structure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.338-343
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• 2007

We presented a special method of forging hollow shafts of hard-to-form material, which is composed of piercing with back pressing and hollow shaft extrusion. The presented method was applied to cold forging a bushing of an excavator. The finite element simulation technology was employed for developing the optimized process and the predictions were compared with the experiments. The method was also applied to an automotive part and was verified to be powerful for manufacturing the cold forged hollow shafts of the hard-to-form materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1293-1297
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• 2006

In this paper, kinematic analysis of a double-action link-type die set for enclosed die forging is carried out. The structure of the die set and its operational principle during enclosed die forging are introduced in detail. A closed-form solution of the relative velocity of the middle plate with respect to the upper plate after the upper and lower dies are enclosed is given in terms of the link lengths and the distance from the lower pin to the upper pin of the link system. The effect of the link lengths on both strokes and velocities is investigated. It has been shown that the relative velocity of the middle plate with respect to the upper plate varies almost linearly with the stroke of the upper plate.