• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2042-2049
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• 2000

This paper is concerned with the comparison of forging characteristics between forward and backward processes, through the three-dimensional finite element simulation, for the aluminum powder forging of engine pistons. Starting from the theoretical formulation of velocity and temperature fields in the sintered preform during the process, we examine the comparative distributions of relative density, effective stress and temperature as well as the variations of total forging load and total volume reduction. Through the comparative results, we find out that the forward method provides better forging characteristics than the backward method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1513-1516
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• 2003

A crank throw, which is one of the crankshaft part for a large diesel engine is manufactured by closed die forging or open die forging. For the purpose of improvement of productivity the open die forging is usually adopted these days. However it has disadvantage of low yield ratio compare to closed die forging. To overcome this problem, the material properties for hot top and bottom zones of ingot are investigated to utilize them to the product and a modified forging process to reduce the material loss of ingot body through forging analysis according to forging factors(a , R, Ø$\sub$B/, Ø$\sub$D/) is suggested.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.126-129
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• 1998

Proper design of blocker dies is one of the most important aspect of impression and closed-die forging to achieve adequate metal distribution. Determination of the blocker configuration is a very difficult task and is art in itself, requiring skills achieved only by years of extensive experience. To save the cost and time of blocker design, many methods using computer were proposed. In this research, low pass filter method proposed by Oh etc. was applied to blocker die design of spoiler support, part of aircraft and plasticine model experiment of closed die forging of spoiler support was accomplished to verify the validity of the blocker designed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1583-1589
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• 2001

Metal matrix composites with whisker reinforcements have significant potentials for demanding mechanical applications including defense, aerospace, and automotive industries. Especially metal matrix composites, which are reinforced with aluminum borate whisker, have been used leer the part of piston head in automobile because of good specific strength and wear resistance. In this study, AC4CH-based metal matrix composites with $Al_{18}$B$_{4}$ $O_{33}$ reinforcement have been produced using squeeze casting method, after T6 heat treatment, we evaluated fatigue life property of matrix and MMC composite and investigated fracture mechanism.m.

• 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)

• Journal of Powder Materials
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• v.7 no.1
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• pp.27-34
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• 2000

The fabrication process and mechanical properties of SiC particle prefrrms with high volume fraction ranged 50∼71% were investigated to make metal matrix composites for possible applications as heat sinks in electronic packares. The SiC particle preforms with 50∼71vol% of reinforcement were fabricated by a new modified process named ball milling and pressing method. The SiC particle performs were fabricated by ball milling of SiC particles with single sized of 48${\mu}$m in diameter or two different size of 8${\mu}$m and 48${\mu}$min diameter, with collodal SiO2 as inorgnic binder in distilled water, and the mixed slurries were cold pressed for consolidation into final prefom. The compressive strengths og calcined SiC particle prefoms increased from 20MPa to 155MPa with increasing the content of inorganis binder, temperature and time for calcination. The increase of compressive strength of SiC particle bridge the interfaces of two neighboring SiC particles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1117-1125
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• 1994

A UBET program is developed for determining the optimum sizes of preform of a rib-web part in axisymmetric closed-die forging. The program consists of forward and backward tracing processes. In forward process, material flow, degree of die filling, and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet and preform are determined from the final-shape data without flash. The above program is easy to handle input data with and is convenient to visualize the whole process of closed-die forging with. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

• Journal of Powder Materials
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• v.2 no.1
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• pp.19-28
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• 1995

Powder forging is a combined technology of powder metallurgy and precision hot forging. Recently, the technology is developing rapidly because of its economic merits, especially in automotive part manufacturing. In the present study, the finite element technique was developed to predict density variation during P/M forging and the technique was applied to analysis of forging of a P/M connecting rod. Although deformation mode of the connecting rod was quite complex, several sections were selected and analyzed under an assumption of asymmetric or plane strain deformation. It was found that some modifications were necessary on the cross section of the beam portion. Therefore, the cross section was modified repeatedly until a satisfactory result of the analysis was obtained. On the other hand, no modifications were necessary in the ring and the pin portions. It is anticipated that the developed technique can be used to optimize preform design and manufacturing processes in P/M forging, which are highly critical to produce successful products in practice.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.428-431
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• 2005

This paper describes the process design for hot forging of bearing hub. Forging processes of bearing hub are simulated using the rigid-plastic finite element method. In the process called closed die forging without flash, the design of blocker geometry is of critical importance. Forging processes designs are take advantage of computer aided Process planning and experts. But that is difficult to predict metal flow line. So the preform is designed by the expert, and modified through predict metal flow line by CAE. This paper is to approach preform design considered defect such as metal flow and unfitting etc. at the finisher process.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.83-92
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• 1998

In this paper, an experimental study has been carried out to develop an aluminum forged piston which has good mechanical properties. Through the experiment, the cavity filling, microstructure and mechanical properties of the final product are investigated with respect to chosen process parameters, which are die shape, heat-treatment condition and preform shape. The mechanical properties of the forged piston are compared with these of the cast piston. As the results, an appropriate die-shape is obtained to produce a perfect piston. The suitable heat-treatment condition and preform-shape are found to good hardness and minute microstructure in the forged piston. And we could obtain the mechanical properties(tensile strength, elongation and hardness) of the forged piston are superior to these of the cast piston.