• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.769-772
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• 2005

This paper deals with the aspects of die design for the multistage fine tooth hub gear in the cold forging process. In order to manufacture the cold forged product fur the precision hub gear used as the ARD 370 system of bicycle, it examines the influences of different designs on the metal flow through experiments and FE-simulation. To find the combination of design parameters which minimize the damage value, the low gear length, upper gear length and inner diameter as design parameters are considered. An orthogonal fraction factorial experiment is employed to study the influence of each parameter on the objective function or characteristics. The optimal punch shape of fine tooth hub gear is designed using the results of FE-simulation and the artificial neural network. To verify the optimal punch shape, the experiments of the cold forging of the hub gear are executed.

• 대한기계학회논문집A
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• 제36권9호
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• pp.1073-1080
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• 2012

점진성형은 공구 운동으로 소재의 국부 소성변형 영역을 전체 소재에 확장시켜 목표 형상으로 변형시키는 냉간 성형공정이다. 본 논문에서는 점진성형의 유한요소해석 시 묘사기법에 관한 연구를 수행하였다. 고찰할 묘사기법으로 라그랑지언 묘사법과 ALE 묘사법을 선택하였다. 미끄럼 경계기법도 공구와 접촉표면에서 요소의 찌그러짐을 극복하기 위한 방법중의 한가지 경우로 고찰하였다. 묘사기법과 경계기법의 다양한 조합 중에 ALE 묘사법과 연계한 미끄럼 경계기법의 경우가 요소의 찌그러짐을 가장 완화 시켰다. 이 방법이 최종 단계 변형까지 점진성형 해석을 지속할 수 있도록 해주는 유일한 조합인 것으로 나타났다. 이에 반해, 라그랑지언 묘사법 및 순수 ALE 묘사법은 점진성형 해석 중에 요소의 찌그러짐이 극심하여 최종 변형 형상에 도달하기 오래 전에 해석이 중단되는 상태를 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.851-852
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• 2008

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.983-987
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• 2001

This paper deals with an automated computer-aided process planning system by which designer can determine operation sequences even if they have little experience in process planning of wheel bolt products by a multi-stage former. The approach to the system is based on knowledge-based rules and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLISP for the AutoCAD using a personal computer and are composed of two main modules. An attempt is made to link programs incorporationg a number of expert design rules to form a useful package. Results obtained using the modules enable the designer and manufacturer of wheel bolt product to be more efficient in this field.

• 소성∙가공
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• 제18권4호
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• pp.342-346
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• 2009

Forming characteristics for the bundle extrusion of Cu-Ti bimetal wires are investigated, which can identify the process conditions for weak mechanical bonding at the contact surface during the direct extrusion of a Cu-Ti bimetal wire bundle. Bonding mechanism between Cu and Ti is assumed as a cold pressure welding. Then, the plastic deformation at the contact zone causes mechanical bonding and a new bonding criterion for pressure welding is developed as a function of the principal stretch ratio and normal pressure at the contact surface by analyzing micro local extrusion at the contact zone. The averaged deformation behavior of Cu-Ti bimetal wire is adopted as a constitutive behavior at a material point in the finite element analysis of Cu-Ti wire bundle extrusion. Various process conditions for bundle extrusions are examined. The deformation histories at the three points, near the surface, in the middle and near the center, in the cross section of a bundle are traced and the proposed new bonding criterion is applied to predict whether the mechanical bonding at the Cu-Ti contact surface happens. Finally, a process map for the direct extrusion of Cu-Ti bimetal wire bundle is proposed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 제4회 압출 및 인발가공 심포지엄
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• pp.1-12
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• 2001

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. Finally, the model experiment results are in good agreement with the FE simulation ones.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.91-97
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• 2004

The drawbead is one of the most important factors in sheet metal forming for automotive parts. So clarifying the friction characteristics between sheets and drawbead is essential to improve the formability of sheet metal. Therefore in this study, drawbead friction test was performed at various bead materials(FC300, HC891, FCD550, HD700, HK600, HK700, SKD11) and surface treatment of beads(Base, induction hardening, Cr plating, ion nitriding, Toyoda diffusion process, TiCN, TiN, CrN). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by surface treatment.

• 소성∙가공
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• 제17권1호
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• pp.5-8
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• 2008

As the semi-solid forming technology has a lot of advantages compared to the die casting, squeeze casting and hot/cold forging, it has been studied actively. This paper focuses on the thixoforging of the rheological materials fabricated by the spiral mechanical stirring equipment with A356 casting aluminum alloy and A6061 wrought aluminum alloy. Formability tests of rheological materials fabricated by spiral mechanical stirring were carried out and the microstructures of forged sample were observed. After thixoforging experiment, the heat-treated conditions of forged samples are investigated to improve the mechanical properties. These results are able to suggest the possibility of commercialization for rheological materials fabricated by spiral mechanical stirring.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.428-432
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• 2010

연소기 챔버 노즐확장부 외피구조물의 성형특성에 대한 연구를 수행하였다. 노즐확장부 외피구조물의 제작에 사용되는 냉간압연 판재가 갖는 이방성 특성을 확인하기 위하여 세 가지 방향의 시편을 제작하여 인장시험을 수행하였으며, 그 결과를 이용하여 Lankford 값을 얻어 구조해석에 적용하였다. 실물형 연소기에 사용될 노즐확장부 외피구조물의 제작 및 성형공정을 통하여 외피구조물의 성형특성을 확인하였으며, 성형으로 얻은 변형률들을 구조해석 결과들과 비교하였다. 본 연구에서 얻은 결과들은 확대비가 더 큰 노즐확장부 제작을 위한 치구 및 성형공정의 설계에 활용될 예정이다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권2호
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• pp.244-251
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• 2011

유한요소법을 통하여 유성압연기에 의한 스테인리스 강관 압연공정을 연구하였다. 3개의 롤에 의한 만네스만 공법을 압연공정에 적용하였다. 보통 유성압연은 냉간가공으로 시작하여 열간가공으로 종료되며, 기존의 압출공정에 비해 공정단축과 생산비절감의 장점을 갖고 있다. 압연공정은 다양하고 복합적인 공정변수를 가지고 있으며, 각각의 변수들은 성형결과에 영향을 미친다. 따라서 유성압연의 다양한 공정변수가 해석에 고려되어야 한다. 본 연구에서는 스테인리스 강관성형의 가능성과 생산성을 검토하였고, 소재예열 및 자전속도, 제품두께 변화를 해석에 반영하였다. 스테인리스 강관 압연공정은 성공적으로 시뮬레이션 되었고 최적의 압연조건을 결정하는데 유용할 것이다.