• 대한기계학회논문집A
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• 제24권10호
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• pp.2610-2618
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• 2000

In this paper, the elastic deformation of cold forging die has been investigated to improve the accuracy of forged parts with FEM analysis and experiments using the strain gages. In the finite element analysis, two types of analysis are used to predict elastic deformation of die. The one is that dies are considered to be elastic body from initial stage to final one, and the other is that the dies are considered to be rigid body during forging simulation and then considered to be elastic body at elastic analysis. Considering the results of analysis and experiments, it is likely that the analytical results are in good agreement with experimental inspections. The method using the elastic assumption of die relatively takes a lot of time to simulate the forming operation. However, It is better that using an elastic die to predict not only the shape of product but also filling of die cavity.

• 한국생산제조학회지
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• 제20권5호
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• pp.582-588
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• 2011

This study was aimed at the design of the dies for the unified shaft joint using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation, 'Deform-3d' and 'Eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the process analysis, we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of die design, we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for multi-forging has been developed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문집
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• pp.93-100
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• 1996

In this paper, a computer simulationtechnique for the forging process having a spring-attached die was presented . The penalty rigid-thermoviscoplastic finite element method was empolyed together with an interatively force-balancing method, in which the convergence was achieved when the forming load and the spring reaction force are in equilibrium within the user-specified allowable accuracy. The force balance was controled by adjusting the velocity of the spring-attched die. th minimize the number of internations, a velocity estimating schemewas proposed. Two application examples found in the related company were given. In the first application example, the predicted metal folw lines were compared with the acturally forged ones. in the second example, a hot forging process with a spring-attached die was simulated and the analyzed results were discussed in order to investigated the effects of spring-attached dies on the metal flow lines and the forming loads.

• Journal of Advanced Marine Engineering and Technology
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• 제40권4호
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• pp.314-319
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• 2016

플랜지 볼트는 체결하중을 분산시키기 위한 와셔와 같은 역할을 하는 플랜지를 가지고 있으며, 주로 냉간단조로 성형된다. 플랜지의 단조 시 꽃무늬 모양의 결함이 발생할 수 있다. 이 결함은 치수 정밀도 및 품질 저하 등의 문제점을 야기할 수 있어 이에 대한 개선이 요구된다. 본 논문에서는 플랜지 볼트의 플라워 형상 결함을 개선하기 위한 금형 설계방법을 제안하고자 하였다. 이를 위해 기존의 단조 공정에서 앞판의 내경을 변수로 금형을 수정하였다. 수정된 금형을 적용한 단조 공정은 상용 유한요소해석 코드인 DEFORM-3D를 이용하여 시뮬레이션 하였고, 해석결과를 기준으로 단조 실험을 하여 결과의 신뢰성을 검증하였다.

• 소성∙가공
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• 제16권4호
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• pp.293-298
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• 2007

Recently, there is a need to produce a large forged part for the flight, shipping, some energies, and military industries, etc. Therefore, an open die forging technique of cast ingots is required to obtain higher quality of large size forged parts. Cogging process is one of the primary stages in many open die forging processes. In the cogging process prior to some open die forging processes, internal cavities have to be eliminated for defect-free. The present work is concerned with the elimination of the internal cavities in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}-3D$. The calculated results of cavity closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• 소성∙가공
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• 제14권8호통권80호
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• pp.675-680
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• 2005

This study was aimed at the design of the dies for the automobile part for the engine oil leakage prevention using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation,'eesy-2-form' of 2D FEM simulation package and 'eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the simulation of 'eesy-2-form', we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of 'eesy-DieOpt', we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for cold forging has been developed.

• 소성∙가공
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• 제19권8호
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• pp.447-451
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• 2010

In this paper, a useful die system for warm plate forging of a large axle housing of heavy-duty trucks is presented. A die system composed of material flow guide pin as well as upper die and lower die is proposed to reduce the inherent thickness reduction along the bent corner of the product which deteriorates structural strength and fatigue life in its service. The role of the pin assembled in the upper die is to prevent formation of sharp corner in early forming stage and to supply material in the lower die cavity sufficient enough to thicken the bent corner at the final stroke. The mechanism of the die system is given and its effect on corner thickness of the product is revealed by two-dimensional finite element analysis under plain strain assumption. Three-dimensional finite element solutions are also given to verify validity of the two dimensional approach and to show the mechanics of the die system in detail. The die system has been successfully applied to manufacturing the axle housing of heavy-duty trucks.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.584-588
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• 1997

Lots of forginfs used in automobile and aerospce industries are made in hot or cold working conditions, depending on the size and shape of a product. Usually the die design for new items has been first made on the basis of experiences and many know-hows accumulated in the company and then slightly modified through trial and error method to get the desired forgings without defects. Most of drawings at the die design stage have been manually drawn, butrecently some of forging companies have begun to apply a computer-aided drafting technique to the die design for reducing drafting time as well as repeatedly utilizing standardized parts form registerd data base. In this paper the automated die design technique for forward extrusion of axisymmetric forgings is developed by using AutoLISP language. For this study the representative die system is determined form the investigation of several types of forging dies being currently employed in the metal forming field and the design rules for cold extrusion die are summarized and programmed on a personal computer. A few design examples of forward extrusion die are given and discusses.

• 소성∙가공
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• 제22권4호
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• pp.204-215
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• 2013

As a pressure vessel, a small seamless aluminum liner with inner volume of about 6.75L is made from an initial billet material of AA6061-O. To produce the aluminum liner, warm forging including backward extrusion and head nosing was numerically simulated using a billet initially pre-heated to about $480^{\circ}C$. Compression tests on the billet material were performed at various temperatures and strain rates, and the measured mechanical properties were used in the numerical simulations. For the backward extrusion and the head nosing, the tool geometries were designed based on the desired configuration of the aluminum liner. Furthermore, the structural integrity of the tooling was evaluated to ensure adequate tool life. The seamless aluminum liner has an endurance limit of about 1.47MPa ($15Kg_f/cm^2$), estimated based on the required inner pressure. The results confirm that the small seamless aluminum liner of AA6061-O can be successfully made by using the two stage warm forging procedures without any bursting failures.

• 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.