• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.315-318
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• 1995

The optimum design problem of a coat-hanger die is solved by the inverse formulation. The flow in the die is analyzed using three-dimensional model. The new model for the manifold geometry is developed for the inverse formulation. The inverse problem for the optimum die geometry is formed as the optimization problem whose objective function is the linear combination of the square sum of pressure gradient deviation at die exit and the penalty function relating to the measure of non-smoothness of solution. From the several iterative solutions of the optimization problem, the optimum solution can be obtained automatically while producing the uniform flow rate distribution at die exit.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.220-223
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• 1998

The failure of die often occurs as a result of growth of microcracks - referred as a brittle damage. In this study, an analysis of brittle damage evolution cupled with elastic finite element analysis of die deformation is presented. A local transformation from the tractions of a workpiece mesh to those of a die mesh is developed. The brittle damage is defined as a vector considering the shape of common microcracks in the brittle metals and the damage function suggested by Krajcinovic is utillized. Applications of the proposed model to modeling damage evolution in the extrusion die and forging die are given and the characteristics of brittle damage evolution in die are in detail examined.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.108-111
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• 1999

Elastic deformation of die has been investigated to improve the accuracy of cold forged parts. In order to improve the accuracy of forged parts we have investigated the elastic deformation of forging die by analysis with commercial. F. E. M code DEFORM and experiments using he strain gages. In the F. E. M analysis two types are used for elastic deformation of die. the one considers die as elastic body and the other considers the die as rigid body. The latter relatively takes a lot of time. The results from the two types are very similar with each other. Considering the results of analysis and experiments it is likely that the elastic strain of forging die is very small.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.115-118
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• 1999

The twisting and bending extrusion process is developed by the $DEFORM^TM$-3D. Because the rectangular section of the extruded product has the symmetry line of cross-section area, the twisting and the bending of extruded product has not occurred. The product with the rectangular section is applied to the twisting and bending extrusion process through the twisted die surface and eccentricity die section. It is shown that the twisting of extruded product is caused by the twisted die surfaces and the bending of extruded product is causd by the eccentricity between the die section. The results by the analysis show that the twisting angle and the curvature of extruded products increases by the die twisting angle, the eccentricity, but decreases by the die length, and friction condition

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.254-257
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• 1998

The twisting and the bending of extruded product are caused by the shapes of products and by the shapes of die surfaces and by the shapes of die land. Because the elliptical shape and the circular shape of the extruded product have the symmetry line of cross-section area, the twisting and the bending of product has not occurred. But the analysis by the DEFORM-3DTM show that the twisting and the bending of extruded product can be occurred by the twisting of the twisting of the die land and by the curving of the die land. The results by the analysis show that the twisting angle of the extruded procduct increases by the twisting angle of the die land and the curvature of the extruded products increases by the radius of bending of the die land.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.82-85
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• 2005

In order to see the effect of die deformation on the forming of sheet metal, the draw-ins, strains, and springbacks of an automotive fender panels are numerically simulated considering the die deformation found by the simultaneous structural analysis of press and dies. The comparison of the forming analysis result between the rigid die and the deformed die layout shows that the deformed tool provides more accurate forming and springback result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2009-2014
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• 2012

It is very important to minimize the die roll height of gear, in order to maximize the shear cutting surface(tooth surface) of fine blanking. In this paper, the fine blanking tool sets were manufactured in order to study the die roll height according to V-ring position and die chamfer shape. They were constituted of the various die inserts and guide plate inserts with different die chamfer shape and different V-ring distance. The fine blanking experiment was conducted with the fine blanking tool sets and the die roll height of the gear samples was measured. It should be noted that die roll height on the fine blanked gear increased with increasing the V-ring distance and die chamfer angle.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.408-413
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• 2003

Dies may have to be replaced for a number of reasons, such as changes in dimensions due to die wear or plastic deformation, deterioration of the surface finish, break down of lubrication and cracking or breakage. In this paper, die cooling methods have been suggested to improve die service life considering die wear and plastic deformation in hot forging process. The yield strength of die decreases at higher temperatures and is dependent on hardness. Also, to evaluate die life due to wear, modified Archard's wear model has been proposed by considering the thermal softening of die expressed in terms of the main tempering curve. It was found that the use of die with cooling hole was more effective than that of direct cooling method to increase the die service life for spindle component.

• Transactions of Materials Processing
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• v.9 no.5
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• pp.533-538
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• 2000

This study has been carried out to develop a CRT die using hot forging. The conventional CRT die made by casting has defects such as void and inclusion. These defects of the cast die make micro-spots on the surface of the CRT which affect the quality of the final product. So, a hot forging process is developed to avoid these defects of CRT die by the model material test and the rigid-plastic FEM. Firstly, model material tests are carried out with plasticine billets in order to investigate the material flow pattern in the die cavity and to get the reasonable initial values for designing the preform in the FE simulation. And then a finite element analysis has been performed to Predict the preform and the forging load of a CRT die. We also suggest an integrated die-set which combines two die-sets into one die-set to save manufacturing time and cost in case of similar die-size.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.61-65
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• 2015

We have fabricated poly(3,4-ethylenedioxythiophene) : poly(4-styrenesulfonate) (PEDOT : PSS) thin films using a slotdie coater for the applications of OLED lightings. It is demonstrated that the properties of slot-die coated PEDOT : PSS films are comparable with those of spin-coated ones. Namely, the average and peak-to-peak roughness of the slot-die coated 50-nm-thick PEDOT : PSS film are measured to be as low as 0.247 nm and 1.3 nm, respectively. Moreover, we have obtained excellent thickness uniformity (~1.91%). With the slot-die coated PEDOT : PSS films, we have fabricated green phosphorescent OLED devices. For comparison, we have also fabricated OLED devices with spin-coated PEDOT : PSS films. Both show almost no discrepancy in device performance. The power efficiency (25.4 lm/W) and emission uniformity (77%) of OLEDs with slot-die coated PEDOT : PSS films are shown to be slightly lower than those (27.3 lm/W, 80%) of OLEDs with spin-coated PEDOT : PSS films at the luminance of 1,000nit, increasing the feasibility of using a slot-die coating process for the fabrication of large-area OLED lighting sources at a competitive price.