• 소성∙가공
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• 제18권3호
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• pp.236-244
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• 2009

In response to growing environmental and collision-safety concerns, the automotive industry has gradually used high-strength and ultla-high-strength steels to reduce the weight of automobiles. In order to overcome inherent process disadvantages of these materials such as poor formability and high springback at room temperature, hot forming has recently been developed and adopted to produce some important structural parts in automobiles. This method enables manufacturing of components with complex geometric shapes with minimal springback. In addition, a quenching process may enhance the material strength by more than two times. This paper investigates mechanical and forming characteristics of high-strength boron-alloyed steel with hot forming, in terms of hardness, microstructure, residual stress, and springback. In order to compare with experimental results, a finite element analysis of hot forming process coupled with phase transformation and heat transfer was carried out using DEFORM-3D V6.1 and also, to predict high temperature mechanical properties and flow curves for different phases, a material properties modeler, JMatPro was used.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.199-203
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• 1995

The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net- shape products using light and hardly formable materials, the SSF process is composed of slug heating, forming, compression holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. The compression holding time that can affect mechanical properties and shape of products is important to make decision, where it is necessary to find overall hert transfer coefficeient properly which has large effect on heat transfer between slug and die. This paper presents the procedure to predict compression holding time of octaining the final shaped part with information of temperature and solid fraction for a cylindrical slug at compression hoiding step in closed-die compression process using heat transfer analysis considering latent heat by means of finite element method. The influence of the predicted compression hoiding time on mechanical properties of products is finally investigated by experiment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 고액공존금속의 성형기술 심포지엄
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• pp.174-182
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• 1997

The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net-shape products using light and hardly formable materials. Generally, the SSF process is composed of slug heating, forming, compression -holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. The compression holding time that can affect microstructural characteristics and shape of products is important to make decision, where it is necessary to find overall heat transfer coefficient properly which has large effect on heat transfer between slug and die. This paper presents the procedure to predict compression holding time of obtaining the final shaped part with information of temperature and solid fraction for a cylindrical slug at compression holding step in closed-die compression process using heat transfer analysis considering latent heat by means of finite element method. The influence of the predicted compression holding time on microstructural characteristics of products is finally investigated by experiment.

• 소성∙가공
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• 제17권1호
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• pp.27-34
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• 2008

In order to manufacture a doubly curved sheet metal, the incremental roll forming process which adopts advantages such as the flexibility of the incremental forming process and continuous bending deformation of the roll forming process has been experimentally investigated. An experimental equipment was developed which was named as unit roll set (URS) consisting of two pairs of support rolls and an upper center roll. The upper roll equipped with the servo control unit is motor-driven and can be positioned in the vertical direction according to the user's commands. Four support rolls are idle, and they freely rotate only along the axis so as to transfer the plate more stably in the tangential direction of the rotation of the driving roll. In the process, the plate is deformed incrementally as deformation proceeds simultaneously in longitudinal and transverse directions. Through the experiments using URS, information regarding to forming schedules is found out to fabricate curved hull plates. This study demonstrates the further application of the incremental roll forming process in shipbuilding industries.

• 한국정밀공학회지
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• 제14권4호
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• pp.72-77
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• 1997

In the temperature analysis of hot metal forming process, the heat transfer conditions between the work-piece and the tool have improtant influences upon the temperature distribution. The accuracy of thermal analysis depends on the proper description of boundary conditions including heat transfer. At the contact surface of two materials with different temperatures, this requires the knowledge of the overall heat transfer coefficient. In order to determine the overall heat transfer coefficient, a technique is developed. The technique involves temperature measurement by using thermocouples during hot upsetting operations and finite element computation. The overall heat transfer coefficient is determined using a non-linear optimization technique.

• 대한화학회지
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• 제11권4호
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• pp.121-125
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• 1967

各種 아민과 할로겐化合物間의 Charge Transfer Complex 形成與否를 檢討하여 보았다. Pyridine Tridthylamine, Piperidine Ethanolamine Triethanolamine, Aniline, Diethylamine 等의 아민類와 四鹽化炭素 또는 클로로폼의 混合溶液을 n-Hexane 溶媒存在下에서 紫外線吸收 스펙트라를 檢査한 結果 장파장쪽의 Shift가 있었으며 特히 Diethylamine과 Triethylamine은 클로로폼 또는 四鹽化炭素와 1:1 Charge Transfer Complex를 形成하였고, Piperidine은 接觸的 Complex를 形成하는 것이 確認되었다. Complex의 形成경향과 아민의 Nucleophilicity와의 關係를 論議하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.83-94
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• 1998

An analysis system for sheet metal forming has been developed to improve the design and tryout process by predicting the deformation behaviour more precisely. This analysis system consists of forming analysis, springback analysis and post processor modules. The more accurate prediction of stress history can be achived due to the improved contact algorithm. Successive simulation of several processes can be carried out conveniently without interrupt by the improved data management of the developed system. The error of data transfer between forming analysis and springback analysis is minimized using the proper shell element. Several benchmark test results and practical results are presented to show the effectiveness and reliability of this program.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.191-197
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• 2016

RCAR low speed impact test estimates repair cost of the impacted vehicle. In this study, for a mid-size vehicle front body model, structural performance for RCAR low speed impact were analyzed with changing the bumper stay shape and size. First, for improving the impact load transfer mechanism to side member the stay rear section shape at connecting area with side member was modified and the stay outer was redesigned to be normal to the barrier. Next, the investigation on stay thickness effect was carried out and the performances of several models with different forming shape were compared. The final design showed 13mm decrease in the maximum barrier intrusion distance and greatly reduced side member deformation. Additional analyses explained the validity of the final design.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.156-160
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• 1996

In this study of made Unloader is moving linear transfer system for mainly plastic working or forming of small electronic unit and other at press line. This machine for lading and unloading a workpiece has been installed in a press in order to load and unload a workpiece form a press die. Control method be used PLC. it took data of input from each sensor and send signal of output to actuator today we have a lot of problem at work of press line. most of press work be operated by human so they often hurted terreble accident by press machine. Because press working system in automotive factories are now changing over to a transfer press working system this Unloader will give more easily and speedy production and manpower saving less of pruduction cost high perfomance

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.289-292
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• 2007

To prevent the damage of glass lens molds and deterioration of glass lenses using in progressive GMP process, a thermal stress and a deformation of the glass lens molds at forming temperature should be considered in the design step. In this study, as a fundamental study to develop a multi cavity mold used in an aspheric glass lens molding, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally, using analysis results, we estimated the thermal stress in a glass lens mold and predicted a modified height of guide ring that determines the forming height of a glass lens.