• 한국산학기술학회논문지
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• 제17권11호
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• pp.223-229
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• 2016

본 연구에서는 엔진의 밸브트레인에 적용되는 롤러 태핏 하우징의 냉간단조 공정을 개발하였다. 시제품을 제작하였으며, 태핏 하우징의 내구성 평가를 통하여 작동성을 확인하였다. 소재 시편의 압축시험을 통하여 태핏에 사용되는 소재의 물성을 확보하고 상용 소프트웨어인 Deform-3D을 이용하여 단조해석을 수행하였다. 해석결과를 바탕으로 냉간단조 공정을 설계하였으며, 실제 금형을 제작하고 시제품을 제작하였다. 제작한 시제품의 평가를 위하여 치수정밀도, 표면조도, 평행도, 동심도를 확인하였으며, 목표한 항목에 모두 부합하는 결과를 확인하였다. 또한 제품의 작동성 및 내구성 평가를 수행하기 위하여, 엔진 밸브트레인의 구동을 모사하는 별도의 시험장치 개발을 완료하였다. 디젤엔진의 아이들 상태를 가정하여 작동성을 평가하고, 엔진의 최고 회전수를 가정하여 내구성 시험을 진행하였다. 시험결과 태핏하우징의 마모는 시험 전, 후 외경 치수 0.002 mm 감소로, 미소한 마모를 보였다. 본 연구를 통하여 정밀 냉간단조 기술을 이용한 제품개발 프로세스를 정립하였다. 또한 본 연구에서 개발한 작동성 평가 시험기를 통해 밸브트레인용 부품의 작동성 및 내구성 평가 시험이 가능할 것으로 사료된다.

• 소성∙가공
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• 제19권1호
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• pp.50-58
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• 2010

In order to successfully implement hot die forging process for the large-size titanium alloy products, it is necessary to devise a customized heating method for the billets and the die tools, as well as the die tool design. This study aims at establishing a hot die forging process of the large-size titanium alloy container products by applying the warm die, semi-hot die and hot die forging process step-wise. To accomplish this purpose, forging mechanism and the die tools were designed considering the strength of die materials at the given die heating temperature. The movable heating devices for the billet and the die tools were also introduced to prevent overcooling of billet and die tools. To verify the applicability of the designed forging process, real-size forging tests were carried out and the quality of forged products, including dimension, surface condition, microstructure and the mechanical properties was evaluated.

• 한국기계가공학회지
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• 제19권5호
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• pp.82-90
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• 2020

Due to the complicated shape of the spider, the production method was changed from cold to warm forging. Finite element analysis was performed to predict the forging load and shape using the enclosed hydraulic die set. As the forging load increases due to the spider die volume, die stress analyses were performed to optimize the die design in order to reduce the die stress in various conditions. Large deformation while producing the complicated forging parts induces high forging load, which is one of the main parameters of the forging surface defects. The forging process was analyzed to find out the root cause of the surface defects generated during the spider production for various parameters, thereby revealing that the radius of die in the defect zone influenced the air trap depth, being the root cause of the surface defect. It was verified that die life was increased and the surface defect was eliminated by changing the die design during the mass production test.

• Advances in concrete construction
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• 제6권5호
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• pp.509-525
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• 2018

In this paper the application of forging process as benefit technique in Reinforced Concrete (RC) beam bars and comparison to lap splices was experimentally investigated with four concrete beam specimens with same dimensions and reinforcement details. The reference specimen was with no splices and the other three beams were with different splices (100% forging in the middle, 50% forging, and 100% lap splices in the middle). Beams were tested with the four points load system. Experimental test results indicated that using forging process as new bar splicing method can have high effects on increasing ductility and energy dissipation of concrete structures. It also proved that this method increased the flexural rigidity, energy absorption, and ductility of the RC beams. And also this research results showed that the flexural capacity and ductility of the beam with 50% forging were respectively increased up to 10% and 75% comparing to that of reference specimen, but the energy absorption of this beams was decreased up to 27%. The ductility of beam with 50% forging was increased up to 25% comparing the ductility of beam with 100% forging.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.195-198
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• 2003

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Applying the dynamic materials and proposed by Prasad et al., it was possible to determine the characteristics of deformation behavior effectively at a given condition of deformation. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. Flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating was found to improve significantly the FEA solutions in predicting the forming load and the distribution of recrystallized volume fraction after forging.

• 소성∙가공
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• 제8권2호
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• pp.216-221
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• 1999

In this paper, an application-oriented approach to piercing analysis in automatic forging simulation by the rigid-viscoplastic finite element mehtod is presented. In the presented approach, the accumulated damage is traced and the piercing instant is determined when the accumulated damage reaches the critical damage value. A method of obtaining the critical damage value by comparing the tensile test result with the analysis one is given. The presented approach is verified by experiments and applied to automatic simulation of a sequence of 6-stage forging processes.

• 소성∙가공
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• 제12권4호
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• pp.308-313
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• 2003

High temperature deformation and softening behavior of SAF 2507 super duplex stainless steel (SDSS) has been investigated in connection with an FEM analysis of hot forging process. Flow curves at various strain rates and temperatures were determined first from compression tests, and the kinetics of dynamic recrystallization were also formulated through the analysis of load relaxation test results. Using the dynamic materials theory proposed by Prasad, the deformation behavior was effectively determined for various conditions. Constitutive relations and recrystallization kinetics formulated from the test results were then implemented in a commercial FEM code. The forming load as well as the distribution of recrystallized volume fraction after forging was successfully predicted by means of the flow stress compensation formulated upon the volume fraction of recrystallization and adiabatic heating.

• 소성∙가공
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• 제12권5호
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• pp.473-478
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• 2003

This study presents the enhancement of forgeability of SNCM522H materials. Target parts are output shaft(OP shaft) used as components of power train for automobiles. To carry out cold forging process of OP shaft by 1 pass instead of existing 2 pass process, studies in terms of process design and heat treatment were performed. To introduce the new process, the finite element method was accomplished, and to assess the validity of proposed heat treatment cycle, several experiments(hardness test, observation of optical microstructures, tensile test) were carried out. The 2Pass forging process could be reduced as lPass process through improvement of process and heat treatment technology and that would give cost reduction.

• 소성∙가공
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• 제7권5호
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• pp.426-431
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• 1998

This study is concerned with cold repressing of sintered preforms by the rotary forging process. An experiment has been carried out using the rotary powder forging press(500kN) which was designed and constructed in the authors' laboratory. The effect of process variables and aspect ration of sintered preform on the densification behavior during the rotary repressing was studied by several mechanical test such as working force hardness distribution density and microstructures of the specimens. Since a higher densification can be achieved by applying the rotary repressing on presinted preforms it was successively demonstrated that the cold rotary powder forging is an effective operation to improve quality of P/M parts.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.627-632
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• 2001

Nimonic 80A superalloy with high-temperature strength and high corrosion-resistance is used in jet engine for aircraft, gas turbine for power plant and marine diesel engine, etc. To develop the manufacturing process of exhaust valve for large diesel engine using Nimonic 80A, various mechanical tests, such as hot compression, microstructure and hardness test have been performed. This results effectively used to set the reasonable forging conditions while hot forging of Nimonic 80A superalloy. Open die and closed die forging experiments are carried out from ESR ingot and finally get a good shaped exhaust valve product.