• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.192-198
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• 2005

In this paper, a systematic attempt for estimating geometric dimensions of cold forgings is made by finite element method and a practical approach is presented. In the approach, the forging process is simulated by a rigid-plastic finite element method under the assumption that the die is rigid. With the information obtained from the forging simulation, die structural analysis and springback analysis of the material are carried out. In the springback analysis, both mechanical load and thermal load are considered. The mechanical load Is applied by unloading the forming load elastically and the thermal load is by cooling the increased temperature due to the plastic work to the room temperature. All the results are added to predict the final dimensions of the cold forged product. The predicted dimensions are compared with the experiments. The comparison has revealed that predicted results are acceptable in the application sense.

• Design & Manufacturing
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• 제8권1호
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• pp.19-22
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• 2014

Today, looking at the trend of product development, interests of injection technology to reduce weldline are growing because of increases of polymer composite materials that containing functional elements and demand of no-painted injection in accordance with environmental regulations. In this paper, surface temperatures of mold increased using high temperature gas for elimination of weldline and characteristics of weldline are analyzed according to mold temperature($60^{\circ}C{\sim}120^{\circ}C$).

• 소성∙가공
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• 제17권7호
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• pp.501-506
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• 2008

In this study, a forming magnesium alloy circular cup was simulated accounting for heat transfer at elevated temperatures. In order to predict the failure of magnesium alloy sheet during simulation, the forming limit diagram, which is used in sheet metal forming analysis to determine the criterion for failure, was investigated. For the failure prediction in the simulation accounting for heat transfer, the forming limit diagram for a temperature the same as the temperature of the blank element was used. The result of the simulation showed that the drawn depth increases with the increase of the die-holder temperature, and is in accord with the experimental results above the die-holder temperature of $150^{\circ}C$. The forming limit diagram provided a good guide for the failure prediction of warm forming simulation accounting for heat transfer. In addition, the effect of the tool shoulder radius on the drawn depth at various tool temperatures is verified using the simulation conditions which agreed with the experimental results.

• Design & Manufacturing
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• 제2권6호
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• pp.43-48
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• 2008

Magnesium alloys have given high attention to the industry of light-weigh as automobile and electronics with aluminium, titanium and composite alloys due to their high strength, low specific density and good damping characteristics. But the magnesium contained structures under high temperature have the problems related to creep deformation and rupture life, which is a reason of developing the new material against creep deformation to use them safely. The purpose of this study is to predict the creep deformation mechanism and rupture time of AZ31 magnesium alloy. For this, creep tests of AZ31 magnesium alloy were done under constant creep load and temperature with the equipment including automatic temperature controller with acquisition computer. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined over the temperature range below 0.5Tm and stress range of 109~187MPa, respectively, in order to investigate the creep behavior. AZ31 Magnesium alloy identify the activation energy for creep deformation and the stress dependence to creep rate at below 0.5Tm, and then investigate the mechanism for creep deformation and creep rupture life of AZ31 Magnesium alloy.

• Design & Manufacturing
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• 제6권1호
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• pp.1-4
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• 2012

Plastic products are producted more than 70% of total processes in the injection molding. The injection molding process has 4 processes such as filling, packing, cooling and ejecting. It spends most of times in the cooling process. Therefore, it is important to control the mold temperature in producing plastic products. The time and system of cooling affect the product's quality and productivity. Especially, cooling time has about 60% of total injection cycle time. Therefore, we can improve a productivity by shortening cooling time. In this study, it was made a comparative study about cooling of linear channels and baffles and observed the variation of mold temperature on the coolant's temperature. As the result, the linear channel's cooling rate had faster than baffles and as coolant's temperature was increased, difference of cooling time was increased. Result of this study will be used widely to design for cooling system of injection mold.

• 한국주조공학회지
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• 제18권3호
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• pp.275-282
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• 1998

The squeeze casting of a Mg-5wt%Al-0.6wt%Zr alloy was carried out to investigate the conditions for the formation and the prevention of macrodefects, such as macrosegregation and shrinkage defects. The effects of the process parameters, the applied pressure, the die temperature, and the pouring temperature on the formation of macrodefcts were investigated in correlation with the evolution of macrostructure. Three types of macrodefects were found; macrosegregation only, shrinkage defects only, both macrosegregation and shrinkage defects. It was found that the pouring temperature, the die temperature, and the applied pressure are closely related to the formation of macrodefects. Sound castings without macrosegregation and shrinkage defects can be obtained under the conditions of 80 MPa$730^{\circ}C$$760^{\circ}C$, and $180^{\circ}C$<$T_D$<$250^{\circ}C$.

• Design & Manufacturing
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• 제1권1호
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• pp.27-32
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• 2007

In the optical application demand for high quality lens is increasing. Plastics lenses are demanded more than glass lenses for large size lenses as well as micro-size lenses. It is difficult to apply typical straight cooling channels of injection mold to lens molding due to its non-uniform temperature distribution. In this study, we manufactured molds for plastic lenses with the conventional cooling channels and conformal cooling channels produced by the DMLS process. We evaluated cooling performance for the 2 molds by injection molding experiment. Also, uniformity of the temperature distribution was tested by infrared camera and temperature monitoring. We confirmed that the cooling performance and temperature uniformity with the conformal cooling channels is much improved from the ones with the conventional. The cooling time with the conformal cooling channels was reduced 30% compared with the conventional cooling channels.

• 한국생산제조학회지
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• 제20권2호
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• pp.151-156
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• 2011

This study examined the casting analysis of fuel pressure regulator of LPI vehicles. We aims to predict all the phenomenon accompanied by flow and solidification in die casting, and maximize productivity and quality through optimal casting design. As a result of comparing Types A and B of casting design, it was found that the number of overflow affected flow, flowspeed and solidification temperature. And there was a minute difference between solidification temperatures at thick section of the spare parts. Solidification began at temperatures of $624^{\circ}C{\sim}630^{\circ}C$ but after the casting was completed, temperatures at the center of the parts were $600^{\circ}C{\sim}614^{\circ}C$ Temperature of molten metal showed optimal flow at temperature of $680^{\circ}C$. It began to solidity around at $650^{\circ}C$ and to be cooled between $580^{\circ}C{\sim}550^{\circ}C$ in high speed. When the process was analysed through a computer simulation, it was found that hardness of regulators manufactured through Type B of overflow was above $H_R60$.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.135-139
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• 2008

Development of surface heating technology using hot jet impingement onto mold inner surface for improvement of pattern transcription. This study is focused on how to control the parameters related to hot jet impingement. The mass flow rate, the jet temperature and the duration of the impingement are major parameters. The nozzle design and other geometric configurations also affect the heat transfer to the surface. In terms of heat transfer analysis, the most important number is the heat transfer coefficient, which is influenced by the mass flow rate, nozzle design, distance between the nozzle tip and the surface. In summary, several parametric studies using the developed model are conducted to investigate the effects of mass flow rate, jet temperature and Heating Time in Surface heating technology using hot jet impingement onto mold.

• Design & Manufacturing
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• 제2권4호
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• pp.48-53
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• 2008

We injection molded a thin type of plate and wedge type of plate with micro prizm patterns on its surface and investigated the fidelity of replication of the micro pattern depending on the process parameter such as mold temperature, melt temperature, injection rate or packing pressure. The size of the $90^{\circ}$ prizm pattern is $50{\mu}m$ and the size of the plate is about $335mm{\times}213mm$ and $400mm{\times}400mm$. The thicknesses are 2.6mm and 0.7mm at each edge of the wedge type of plate and 1mm at each edge of the thin type of plate. The fidelity of the replication turned out quite different according to the process parameters and location of the patterns on the plate. We measured the cavity pressure and temperature in real-time during the molding to analyze the effect of the local melt pressure and temperature on the micro pattern replication.