• 한국정밀공학회지
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• 제15권9호
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• pp.15-24
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• 1998

In this research. we have proposed a new technique to determine .the combination of design parameters for the process design of a hot forged product using artificial neural network(ANN) and statistical design of experiments(DOE). The investigated problem involves the adequate selection of the aspect ratio of billet, the ram velocity and the friction factor as design parameters. An optimal billet satisfying the forming limitation, die filling, load and energy as well as more uniform distribution of effective strain, is determined by applying the ability of artificial neural network and considering the analysis of mean and variation on the functional requirement. This methodology will be helpful in designing and controlling parameters on the shop floor which would yield the best design solution.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.228-232
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• 2001

Fatigue strength, electrical conductivity and stress-corrosion-cracking resistance are considered as important factors at aircraft Al alloys, therefore Al7050 alloy has been developed to improve such properties. However, hammer-forged Al7050 parts showed the undesirable structures such as severe local grain coarsening and inhomogeneous material flow, resulted in the degraded mechanical properties. In this paper, process conditions are investigated for elimination of the grain coarsening and improved material flow during forging process by both of experiments and FEM analysis. Particular interest has been given to understand role of preform shape on the grain coarsening behavior and magnitude of the hammer forging load The use of preform has been beneficial for reduction of the forging load and elimination of the grain coarsening. However, in the cases of as received bar and the round bar, which was machined to 2.5mm thickness in surface layer, some degree of local grain coarsening behavior has been observed. The optimized preform shape could be properly designed by applying the FEM simulation.

• 한국정밀공학회지
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• 제14권8호
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• pp.57-64
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• 1997

The process design of backward and forward extrusion of axisymmetric part has been studied in this paper. The important factors of cold forging process with complex geometry are the design of initial billet shape, the possibility of forming by one-stage operation and the determination of preform shapes, etc. Based on the systematic procedure of process sequence design, the forming operation of cold forged part is analyzed by the commercial finite element program, DEFORM. The design criteria are forming load, geo- metrical filling without defect and a sound distribution of effective strain in final product. It is noted that one step of preform operation is required to obtain the final product. Numerical result is compared with experi- mental one. It is found that the analyzed result is in good agreement with actual forming result.

• 한국정밀공학회지
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• 제13권4호
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• pp.43-52
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• 1996

This paper describes interactive computer procedures for design the forming sequences in cold forging. This system is implemented on the personal computer and its environment is a commercial AutoCAD system. The programming language. AutoLISP, was used for the configuration of the system. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the part is a key in process planning. To recognize the part section geometry, the section entity representation, the section coordinate-redius representation and the section primitive geometru were adopted. This system includes six major modules such as input module, forging design module, forming sequence design module, die design module, FEM verification module and output module which are used independently or in all. The sequence drawing wigh all dimensions, which includes the dimensional tolerances and the proper sequence of operations, can generate under the environment of AutoCAD. The acceptable forming sequences can be verified further, using the FE simulation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제11회 학술강연회논문집
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• pp.17-17
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• 1998

1970년대에 개발된 Ti-15-3 합금은 상온에서 우수한 성형성을 가지고 있어 Ti-6-4 합금보다 성형 공정을 대폭 감소시킬 수 있어 생산비용을 크게 감소시킬 수 있는 장점이 있는 합금이다. 또한, 냉간 성형성이 우수하고 강화 범위가 폭넓기 때문에 항공기의 프레임, 항공기 압력 용기 및 고장력 유압 튜브 등에 많이 사용하고 있으나, 열간 성형성이 Ti-6-4 티타늄 합금보다 좋지 않기 때문에 이제까지의 적용 분야는 판재 성형 등의 한정된 분야에만 적용되어 오고 있는 실정이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.178-182
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• 1995

The technique of neural networks is applied to cold forging design system. A user can select more desirable plans in cold forging design by being advised with expert's opinion from neural networks. The neural networks are learned with 3 parts which are most important in cold forging design-undercut, narrow hole, sharp corner. Using the neural networks, the cold forging design system built in this study determines forming possibility about variable shapes in product. We can get available result using the system.

• Journal of Welding and Joining
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• 제7권2호
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• pp.1-11
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• 1989

주철은 구조물 및 공업재료로써 오랫동안 사용되어 왔으나 이들 용접은 항상 어렵고 특별한 지 식과 기술을 계속 요구하고 있다. 최근 가격면에서 유리한 주철을 주강 및 단조품과 대체하여 사용이 증가하는 추세이다. 이는 주조공정의 고유한 유연성과 함께 합금설계, 주조기술 및 열처 리 분야에서 개선이 이루어지면서 가능해졌다. 이런 개발과 병행하여 주철을 용접할 필요성이 증가되었다. 옛날에는 용접의 어려움 때문에 주철용접은 제조중 생긴 주물결함 보수나 사용도중 생긴 균열에 대한 보수용접으로 국한되었다. 그러나 수년동안의 용접기술 개발과 금속학적인 영향에 대한 지식이 증대됨에 따라 주철끼리 또는 강과의 접합까지 용접의 범위가 넓어졌다. 본고에서는 주철용접을 이해하는데 필수적인 금속학적인 영향들에 대해 주철 종류별로 설명하고 이들을 용접하는데 있어 성공과 실패에 대한 이유등을 실례를 들어 기술하고자 한다.

• 대한기계학회논문집
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• 제12권4호
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• pp.712-720
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• 1988

본 연구에서는 프레스에 의한 축대칭 냉간단조품의 자동공정설계 및 금형설계 를 위한 대화식 프로그램인 "COLD-FORMING"과 "DESIGN-DIE"의 개발에 대하여 설명한다. 프로그램의 능력은 "COLD-FORMING"에서는 (1) 중실부품의 냉간단조에 있어서 작업 순 서의 해석과 각 단계에 포함된 개별작업의 인식 (2)중간 예비성형단계의 형상 및 치수 결정 (3) 각각의 성형단계에서의 성형하중계산 (4) 작업지시서를 위한 그래픽 출력 등 이며, "DESIGN-DIE"에서는 앞의 공정설계에서 구해진 결과를 이용하여 (1) 성형에 필 요한 다이세ㅌ의 형상, 재질 및 최적 치수를 결정 (2) 다이세ㅌ의 그래픽 출력 등을 할 수 있다. 및 최적 치수를 결정 (2) 다이세ㅌ의 그래픽 출력 등을 할 수 있다.

• 소성∙가공
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• 제31권2호
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• pp.51-56
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• 2022

In this study, finite element analyses were performed by applying a stress ring and split die design to relieve the tensile stress acting on the die due to high surface pressure during warm-closed forging. The applied material was a yield-ratio-control-steel (YRCS). It was used without quenching or tempering after forging. In the case of stress rings design, the number of stress rings and the tolerance for shrink fit were different. Vertical and horizontal splits were applied for insert die split design. Case 5 die with three stress rings, 0.2 % shrink fit tolerance, and vertical split was selected as an effective die design for tensile stress reduction. Based on die stress reduction analyses, Case 5 die for warm-closed forging was produced and smooth forgeability was secured, making it possible to manufacture forging product of yoke with the required geometry. In addition, controlled cooling using warm forging heat was applied to secure mechanical properties of yokes. When oil cooling was used for direct controlled cooling after warm-closed forging, a relatively uniform Rockwell hardness distribution and high mechanical properties could be obtained.

• 한국정밀공학회지
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• 제13권3호
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• pp.94-101
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• 1996

This paper presents an investigation of the ability of the scheme to simultaneously accomplish both prediction of fracture initiation and analysis of deformation in cold forged products. The Cockcroft-Latham criterion which is successfully applied to a variety of loading situations is used in the present investigation to estimate if and where surface and internal fracture occur during the deformation process. The numerical predictions and experimental results of two types of fundamental cold metal forming process taken into account are compared. Finite element simulation combined with fracture criterion has successfully predicted the site of surface or internal fracture initiation and corresponding to level of deformation observed experimentally.