• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.796-799
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• 2004

The effects of forming presure, organic binder content and moisture on flexural strength were investigated. As moisture content increased in the granules during compaction, the density and strength of the green body were increased. Green strengths were found to improve more strongly with increasing forming pressure in the case of using the granules of higher organic content. The sintered strength was the highest with the organic content of 0.2wt％ under all forming pressures.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.101-104
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• 2000

Milli-structure components are classified as component group whose size is between macro and micro scale. that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In order to conventional metal forming, where numerical process simulation is already idly applied, the micro-forming process is characterized by some scale effects which have to be considered in an advanced process simulation. milli-structure rectangular cup drawing is analyzed and designed using the finite element method and experiment. The result of the finite element analysis is confirmed by a series of experiment.

• 소성∙가공
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• 제7권4호
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• pp.354-363
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• 1998

In order to analyze the stretch forming characteristics of tailored blanks, laser welded blanks of different thickness and strength combinations were prepared and stretching tests were done. The stretching formability of laser welded blanks was reduced as increasing the deformation restraining force ($strength{\times}thickness$) ratio between two welded sheets. Weld line movement was attributed to strain concentration at weaker sheets and resulted in fracture at weaker sid, so that fracture could be predicted by the forming limit of the weak sheet. In the case of a welded blank with the similar deformation restraining force rations between two welded sheets, crack occurred at weld and its forming limit was about 15% less than the base sheet. The effects of lubrication and weld line position on stretch-ing formability were also investigated by experiments. Lower friction did not always give better formability for tailored blanks. Stretching formability was observed to be improved as increasing the area of weak sheet.

• 소성∙가공
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• 제16권1호
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• pp.67-74
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• 2007

This study is aimed to find out the optimal forming conditions by comparing and analyzing material flow, deformation pattern, and a forming load through rigid-plastic FEM for a flange using pipe. Flanges are widely used for various purposes as connectors of industrial steel pipes which are manufactured by drawing process. The forming feature of flange was reviewed through both heading process and radial extrusion process in a cold working condition. As a result of simulation, the shape of flange can not be made by heading process, but made by radial extrusion process. The effects of design factors, such as gap-height, die-comer radius, and frictional factors on maximum forming load and deformation pattern are investigated for radial extrusion process.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.754-758
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• 2000

Milli-structure components are classified as component group whose size is between macro and micro scale. that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In order to conventional metal forming, where numerical process simulation is already fully applied, the micro-forming process is characterized by some scale effects which have to be considered in an advanced process simulation. milli-structure rectangular cup drawing is analyzed and designed using the finite element method and experiment. The result of the finite element analysis is confirmed by a series of experiments.

• 한국기계가공학회지
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• 제11권4호
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• pp.173-179
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• 2012

In recent years, Magnesium(Mg) and its alloys have become a center of special interest in the automotive industry. Due to their high specific mechanical properties, they offer a significant weight saving potential in modern vehicle constructions. Most Mg alloys show very good machinability and processability, and even the most complicated die casting parts can be easily produced. In this study, Microstructure, Vickers hardness and tensile tests were examined and performed for each specimen to verify effects of forming conditions. Also to verify upsettability and forming limit of the specimen at room temperature and elevated temperature, upsetting experiments were performed. For comparison, experiments at elevated temperature were performed for various Mg alloy, such as AZ31, AZ91, and AM50. The experimental results were compared with those of CAE analysis to propose forming limit of Magnesium alloys.

• 소성∙가공
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• 제13권8호
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• pp.696-703
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• 2004

The purpose of this study is to examine the bulk/sheet forming characteristics of bulk amorphous alloys in the super cooled liquid state. Recently it is reported that amorphous alloys exhibit stress overshoot/undershoot and non-Newtonian behaviors even in the super cooled liquid state. The stress-strain curves with the temperature-dependences as well as strain-rate dependence of Newtonian/non-Newtonian viscosities of amorphous alloys are obtained based on the previous experimental works. Then, those curves are directly used in the thermo-mechanical finite element analyses. Upsetting and deep drawing of amorphous alloys are simulated to examine the effects of process parameters such as friction coefficient, forming speed and temperature. It could be concluded that the superior formability of an amorphous alloy can be obtained by taking the proper forming conditions.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.84-88
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• 2003

In this paper, The optimum design of a die shape has been carried out the FEM analysis of a pilger mill process considering various factors. The pilger mill forming process consists of a pair of rotating die which has appropriate surface shape. The important design parameters of the pilger mill are the feed rate and the profile of grooved die. Optimum design procedure was performed in order to investigated effects on the forming load and the deformed shape of material depending on the die radius profile. Profile of the die surface for the optimum design were suggested with the linear, the cosine and the quadratic curve considering a physical forming process. The surface of each die was modeled using the 3DAutoCAD and the analysis of pilger forming process was performed using the LS-DYNA3D. The optimum profile of the die shape for the pilger mill was determined to the quadratic profile. Since the analysis results provide that the model of the quadratic profile gives the lowest forming load and a proper deformed shape.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.387-390
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• 2006

스피닝은 가장적은 가공력과 간단한 도구를 이용하여 소재를 변형시키는 방법중의 하나이다. 그리고 소재의 소성변형으로 인해 기계적 특성의 향상을 가져오는 공법이다. 이러한 스피닝 공법은 자동차, 항공, 군사 분야에서 중요한 부품의 생산에 적용되는 기술이다. 본 연구에서는 발사체 연료탱크의 돔형상에 스피닝 공법을 적용하여 제작함에 있어 롤러의 이송속도와 소재의 두께감소에 따른 성형력의 경향을 유한요소 해석을 이용하여 분석하였다.

• 소성∙가공
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• 제26권1호
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• pp.35-40
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• 2017

Laser forming is an advanced process in sheet metal forming in which thermal stress originated from the laser heat source is used to shape the metal sheet. However, substantial waiting time is normally necessary for the workpiece to cool down between consecutive scans so that a steep temperature gradient can be reestablished in the next scan. In order to solve this drawback, laser bending characteristics are experimentally implemented in underwater condition. Laser forming effects under various conditions, including different laser power, scanning velocity, beam diameter, number of passes and material, are investigated. The results show that the underwater laser forming facilitates deliberate forming. The bending angle per respective laser scan is decreased with increasing the number of passes and scanning velocity.