• 소성∙가공
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• 제19권7호
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• pp.399-404
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• 2010

We propose an analysis model for simulating the detailed procedure of pore closing in open die forging of shafts. In the analysis model, an artificial symmetric plane is used, on which initial pores are located to be traced. The analysis model is employed to carry out three-dimensional simulation of pore closing in shaft free forging by both conventional free forging press and radial forging machine. With this result, two typical types of free forging equipment for manufacture of shafts are compared in detail. It has shown that the radial forging machine is much superior to the conventional open die forging press especially in pore closing under high hydrostatic pressure with sound strain.

• 한국기계가공학회지
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• 제15권3호
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• pp.28-35
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• 2016

Forging operations are non-stationary processes occurring because of indirect pressure, generally, under conditions of three-dimensional stress and deformation. Furthermore, due to friction and the constraints of die geometry, deformation is not homogeneous. Material flow and deformation are largely determined by the shape of the tools. It is well known that net-shape forging can improve the mechanical strength of the final product as well as reduce material waste. Oxygen-free copper that is used for electrical and electronic components has excellent electrical and thermal conductivity. Oxygen-free copper parts have a low productivity in cutting process. Thus, the forging process is performed in order to improve the low productivity in cutting process. The forging of oxygen-free copper for electrode body parts was modeled using finite element simulation and forging experiments that were conducted for producing electrode body parts at room temperature. In order to reduce the cost of cutting products, the forging was performed in a closed cavity to obtain near-net or net-shape parts.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.37-41
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• 2007

The purpose of this study is to design the free forging tool for the high accuracy of the thrust shaft in marine engine. In order to do it, the principal factor controlling the uprightness of the flange part and the excessive margin and folding in middle part of thrust shaft after forging process was identified using FEA. Based on the results, the optimum shape of free forging tool and working method were proposed and verified through the mock-up and the actual product test.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.50-52
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• 2007

Large size forged parts usually were made by hot open die forging because of the die cost, high applied load and small manufacturing quantities. Cast ingots were used in open die forging and the ingots almost included the cavities in its inside. Therefore, one of the aims for forging processes is to close and remove the cavities. However, its criteria were well not defined since the studies have many difficulties to investigate the cavity behaviors because of its large size. In this study, the cavity closure behavior was investigated by experimental and FE analysis. The FEM analysis is performed to investigate the overlap defect of cast ingots during free forging stage. The measured flow stress data were used to simulate the forging 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 forging, 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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• 제11권5호
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• pp.388-393
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• 2002

Heat-treatment-free steels have been replacing for conventional quenched-and-tempered structural steels since the microalloyed forging steel was developed in early 1970s in Germany. Substantial cost reduction provides the driving force for this change. As a result of intensive R & D efforts and application trials, various kinds of grades, for example heat-treatment-free steels for hot forging, machining and cold heading, have been developed and moreover these steels are in tonnage production throughout the world. The developments in alloy steels, processing conditions and structure-property characteristics of the heat-treatment-free steels, are described and also recent trend and future prospect are summarized in this report.

• 한국해양공학회지
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• 제16권6호
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• pp.49-54
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• 2002

The Finite Element Method is applied to the determination of the deformed bulge profile and strain distribution during upset forming of cylindrical billets. From the results of simulation, the bulging along the z-axis becomes more severe with increasing eight reduction, and with increasing friction at the die-material interface. The present method can be used for the simple prediction of the deformed shape and strain distribution in upset forging of cylindrical billets with dissimilar fictional conditions at the die-material interfaces.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.10-17
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• 2003

The amount of production orders from Japanese car and construction machine industries have slightly increased in 2002, but the costs of the forged parts have decreased due to severe competitions with the other Asian countries. Most of the forging industries and some universities are making more efforts for technological researches and developments to meet the demand for higher accuracy and higher quality products, shortening of delivery time, and development of forged parts for new industrial fields. Some helical gears of which surfaces can be net-shaped have been started for commercial base production to be shipped to car industries. Some non-graphite lubricants for hot forging and some conversion coating free lubricants for cold forging have been developed to improve some environmental problems.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.115-116
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• 2011

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.291-296
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• 2000

The sensitivity method has been applied to find perform shape that results in the desired shape after forging. As a basic example, initial shape of specimen for the cylinder shape without barrelling after forging has been found. The method is then applied to various shapes of 3D free forging and initial shapes of the corresponding specimens after forging have been found successfully. The sensitivity method is proven to be an effective and accurate tool for the preform design.

• 소성∙가공
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• 제10권4호
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• pp.294-301
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• 2001

The sensitivity method has been applied to find perform shape that results in the desired shape after foring. As a 2D example, initial shape of specimen for the cylinder shape without barrelling after forging has been found. The method is then applied to various shapes of 3D free forging and initial shapes of the corresponding specimens after forging have been found successfully The sensitivity method is proven to be an effective and accurate tool for the preform design.