• Proceedings of the KSME Conference
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• 2001.06c
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• pp.106-110
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• 2001

A effective and accurate method of hot-forging process is essential to the design of optimized dies as well as workpiece of intial shape. the former is achieved by a proper forging sequence with invokes serious problem like excessive load and die wear, die failure, underfilling and lap defects. the latter is achieved by a proper preform design of case I, case II, case III. metal forming processes of aluminum-alloy forged at an effective strain and temperature are analyzed by the finite element method. the non-isothermal analysis have been compared with optimized in terms of preform shape.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.44-48
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• 2003

In metal working, cold forging that has profit to satisfy dimension accuracy is using in various manufacturing products. Recently, most of the interest thing is precision forging of gear, Gear forging product is more strength than broaching gear, and it has many advantages with reduction of factory expenses. The reason of difficulty to improve accuracy of gear dimension compare to another products is the dimension accuracy is very high, approximately 10$\mu\textrm{m}$, and because die of involute teeth and elastic strain of forged tool differ from standard curve. This paper represent quantitative analysis of die and teeth of forged tool, namely difference of curves, with experiments and analyze the factor of dimension gap, finally, will design compensated involute curve.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.62-67
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• 1998

An experimental study has been carried out to investigate casting process parameters which influence on the microstructures of cast preforms in casting/forging process of aluminum alloy. In the casting process, pouring temperature, pouring time, mold temperature, mold material, and, cooling method are selected as process parameters. With the cast preform, a forging test has been performed to compare mechanical properties of final products between casting/forging process and forging process. From the experimental results, low mold temperature and water cooling method are favorable for obtaining minute microstructures of cast preforms. Casting defects included in cast preforms. such as pores and shrinkage cavity, are eliminated by the forging process. And comparing cast/forged products with conventionally forged products, the former are almost as same as the latter in mechanical characteristics.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.178-184
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• 2000

To obtain high quality component with thixoforming process, it is important that the homegeneous distribution of solid particles without liquid segregation. In closed-die semi-solid forging process, liquid segregation is strongly affected by injection velocity than any other process variables because the material has to travel relatively long distance to fill the cavity through a narrow gate before solidification begins. The optimal injection velocity and die temperature were investigated to fabricate near-net-shape compressor component called Al frame.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.118-124
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• 1998

The die wear is one of the main factors affecting die accuracy and tool lifetime. It is desired to reduce die wear by developing simulation method to predict wear based on process variables, and then optimizing the process. Therefore, this paper describes methodology of preform design for minimizing wear of finisher die in multi-stage cold forging processes. The finite element method is combined with the routine of wear prediction. The cold forging process is analyzed using developed simulation method. In order to obtain preform to minimize die wear, the Flexible Polyhedron Search(FPS) algorithm is used. The optimal preform shape is found from iterative deformation analysis and wear calculation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.185-190
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• 2000

Die design by computer simulation has some advantages compared with the conventional method which has performed by designer's experiences and trials and errors. The die filling and solidification process of thixoforming process were simulated by MAGMAsoft/thixo module. First of all, thixoforming die design was applied to previously geometry shape. The value of pressure distribution shows high and uniform as the gate diameter is 18mm. Designed gating system considering the deformation of die and product was suggested by the filling simulation. Gate velocity(7.25m/s) of designed gating system shows that propriety to semi-solid metal working process and CAE results were in good agreement with experimental results.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.242-247
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• 1998

The conventional closed-die forging processes had been applied to forging of the spur gears. But this type process requires high pressure. The commercial finite element analysis code ANSYS for the stress and elastic deformation of non-axisymmetric die was adopted in this study. In the non-axisymmetric die such as gear forging, maximum stresses were imposed on the tip of the gear tooth. When the stress exceeds yield strength of insert die, many approaches were attemped to prevent the die failure. Good shaped products are forged successfully. This type process could by used as an advanced technique to replace conventional hobbing process of gear.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.105-112
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• 1996

Aluminium alloy have been used extensively as forging materials for aircraft components due to their high specific strength and corrosion resistance. A large portions of these materials are used as airframe components consisted of various combination of such Rib-Web structure. But the problem of high forging pressure and defect which were caused by narrow Rib thickness prevented from the favorable developments and laboratory scaled trials. In this study, optimization of forging variables such as corner radius and temperature in Rib-Wed structure were established. The 2 mm of corner radius minimized the forging pressure to get the fixed Rib height, which well coincided with theoretical result according to Upper-Bound analysis. And optimum workpiece temperature was below 450$^{\circ}C$ in consideration of grain growth and forging defects by local melting.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.113-121
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• 1996

AI7075 alloy has been used for aircraft components since it has the advantage of high strength, high toughness, and high corrosion resistance. Many airframe components consist of various combinations of rib-web structure. In this study, various process paramenters such as die design, lubricant, ram speed, forging temperature have been investigated using the experiment and F.E.M. simulation to develop the precision forging technology for AI7075. When lubricant is applied to both material and die, shear friction factor is 0.1 which shows best effect of lubricant. It is specific corner radius of die that minimized forging load regarding process conditions, especially according to the ratio of the width of rib and web. In conclusion, optimum corner radius is 2~3mm when the width of rib and web is 3mm and 20mm respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.135-138
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• 2009

In this study we investigate the machining characteristics of tool material for cold forging by using the machining center. The test was in the SKD62 cold forging material by 2-edge endmill with cutting fluid. The coating conditions are depth of cut 1,2,3mm. WC-endmill, federate 20mm/min, cutting velocity 20m/min. The surface roughness increase as the depth of cut increase. Also cutting force increase whiles the depth of cut increase.