• 한국정밀공학회지
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• 제16권11호
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• pp.166-173
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• 1999

Al forged parts are many cases with rib-web section which is difficult to manufacture precisely. Therefore, process conditions must be optimized for precision forging of Al alloys. In this study, various process parameters such as die design, lubricant, ram speed, forging temperature have been investigated using the experiment, upper bound theory and F.E.M. simulation to develop the precision forging technology for rib-web shape component. 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.125-126
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• 2006

The characteristics of the tool system give many effects into the costs and qualities for the finished components. Therefore, a tool life is one of the important issues on cold forging industry. However, since variables related with tool life are many complicated, the studies for solution should be investigated by the systematic research approach. In this study, heat-treatment of tool material is investigated to improve the tool life. Deep cryogenic treatment of tool steel is very efficient to improve the wear resistance due to the fine carbide. And, it is investigated that the shape and dimension of tool give effect into both tool life and quality of forged product.

• 한국정밀공학회지
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• 제12권3호
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• pp.42-52
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• 1995

An UBET(Upper Bound Elemental Techniquel) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flashless non-axisymmetric forging. To analyze the process easily, it is suggested that the deforma- tion is divided into two different parts. Those are axisymmetric part in corner and plane- strain part in lateral. The total power consumption is minimized through combination of two deformation parts by building block method, form which the upper-bound forging load, the flow pattern, the grid pattern, the velocity distribution and the effective strain are deter- mined. To show the merit of flashless forging, the results of flashless and flash-forging processes are compared through theory and experiment. Experiments have been carried out with plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agrement with the experimental results.

• 한국생산제조학회지
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• 제8권4호
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• pp.87-92
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• 1999

Generally the life of die is limited by fatigue fracture or dimensional inaccuracy originated from wear. In this paper to predict the fatigue life of die the stress and strain histories of die can be predicted by the analysis of elastic-plastic finite element method and the elastic analysis of die during the process analysis of workpiece. Also the stress-life curve of die material can be obtained through experiment. With the above to재 facts we propose the analysis method of prediction fatigue life in die,. In the proposed model the analysis of elastic-plastic finite element method for material is carried out by using ABAQUS. Surface force resulted from the contacting border of the die and workpiece is transformed into the nodal force of die to implement elastic analysis. besides the proposed analysis model of die is applied to extrusion die and forging. die.

• 소성∙가공
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• 제7권3호
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• pp.282-290
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• 1998

In bulk metal forming processes prediction of tool life is very important for saving production cost and achieving good material properties. Generally the service life of tools in metal forming process is limited to a large extent by wear, fracture and plastic deformation of tools. In case of hot and warm forging processes tool life depends on wear over 70%. In this study finite element analyses are con-ducted to warm and hot forging by adopting suggested wear model. By comparison of simulation and eal profile of die suggested wear model. By comparison of simulation and real profile of die suggested model is verified.

• 소성∙가공
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• 제7권3호
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• pp.274-281
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• 1998

The service life of tools in metal forming process is to a large extent limited by wear, fatigue fracture and plastic deformation. In elevated temperature forming processes wear is the predominant factor for tool operating life. To predict tool life by wear Achard's model is generally applied. Usually hardness of die is considered to be a function of temperature. But hardness of die is a function of not only tem-perature but also operating time of die. To consider softening of die by repeated operation it is necessary to express hardness of die by a function of a function of temperature and time. By experiment of reheating of die softening curve was obtained and applied to suggest modified Archard's Model in which hardness is a function of main tempering curve.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.111-115
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• 2001

The die design for hot forging was investigated for manufacturing precisely of scroll rotor made with Al-Si alloy. A scroll rotor is a non-symmetric 3-D shape part, having involute wraps. Disk-shaped billet of Al-Si alloy was extruded to wraps and boss simultaneously. Because the involute wraps is not axi-symmetric, the flow velocity and the stress of die is very much different at each portion. Moreover, the die in wraps portion is a cantilever beam and fractured. In this paper, the analysis of forming and die stress is investigated using the FEM tool, DEFORM-3D. The tensile strength of tool material is $250kg/mm^{2}$. From the analysis results, we can find the maximum principal stress of die is over the fracture strength and redesign the die. The prototype forged part is superior in net shaping and microstructure.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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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.

• 한국산학기술학회논문지
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• 제4권1호
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• pp.36-41
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• 2003

열간단조 밀폐금형의 수명연장을 위한 빌릿의 소성변형 유동해석을 유한 요소법에 의하여 실시한 결과 임프레션 형상에 대한 수정설계를 수행하였고, 임프레션 표면 마멸부위의 보수방법을 육성용접에 의한 방법으로 금형을 재생하여 사용한 결과 개발 전의 3,0(H개 생산에서 개발 후 5,000개 양산되었을 때 임프레션 표면을 관찰하였더니 3,000개 정도에서 나타났던 마멸보다 얕은 마멸이 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 제7회 단조 심포지엄
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• pp.93-104
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• 2002