• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.917-920
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• 2005

This paper introduces an optimal design technique for a 250-watt isolation transformer using a recently developed optimization method, dynamic encoding algorithm for searches(DRAS). Although the optimal design technique for transformers dates back to 1970s and local optimization is often undertaken using FEM nowadays, literature concerning global optimization of transformer cores is rarely found against its importance. In this paper, a small isolation transformer is used as a model to be optimized with application of DEAS to corresponding mathematical description. The optimization result confirms that DEAS can be successfully employed to design transformer cores for various design specifications only by changing cost functions.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.191-191
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• 2000

The mechanism of the blowhole and the pit formation in lap-jointed fillet CO₂ arc welds of Zn-coated steel sheet was established by the direct observation of the gas behavior in the molten pool with the high speed camera system. Main conclusions obtained are as follows1) Some blowholes were formed by incomplete back-filling to the pits at the last stage of the solidification. This type of blowhole was formed through four stages of gas in the molten pool, incubation, explosion, back-filling and completion of back-filling stage.2) Most of the pits was back-filled at the last stage of their formation. (Received September 27, 1999)

• Journal of Welding and Joining
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• v.18 no.2
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• pp.64-68
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• 2000

The mechanism of the blowhole and the pit formation in lap-jointed fillet Co₂arc welds of Zn-coated steel sheet was established by the direct observation of the gas behavior in the molten pool with the high speed camera system. Main conclusions obtained are as follows: 1) Some blowholes were formed by incomplete back-filling to the pits at the last stage of the solidification. This type of blowhole was formed through four stages of gas in the molten pool, incubation, explosion, back-filling and completion of back-filling stage. 2) Most of the pits was back-filled at the last stage of their formation.

• Textile Coloration and Finishing
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• v.34 no.3
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• pp.157-164
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• 2022

This study tried to analyze the heat resistance properties by blending epoxy and phenolic resin in a certain ratio, and to analyze the adhesive properties at the time of metal-polymer hetero-adhesion by applying Epoxy-phenolic resin between a silicon steel sheet and m-aramid sheet, the viscosity, adhesive peel strength, and adhesive cross section were measured using a rotational rheometer, a tensile tester(UTM), and a field emission scanning electron microscopy(FE-SEM). The thermal stability and heat resistance were confirmed by measuring the mass loss according to the temperature increase using Thermogravimetric analysis(TGA). After blending with epoxy and Phenolic resin(1:0.25 ratio) curing at 110℃ for 10 min, high adhesive strength was improved more than 40% compared to the adhesive strength using epoxy alone. When the space between the silicon steel sheet and m-aramid sheet, which is created during curing of the E-P blend, is cured with a slight weight, it is possible to control the empty space and improve adhesion.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.58-63
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• 2008

Cold rolled and high strength steel were used for vehicle bodys to satisfy environmental regulation and improve fuel ratio. This paper presented a method far determining the fatigue life of cold rolled steel sheet EZNCEN and high strength steel sheet HS40R spot weldment used in vehicles. We can estimate the fatigue life of the spot weldments from the MSC/FATIGUE using the finite element method. The maximum load is found in the nugget part of both surfaces. The cold rolled steel and the high strength steel showed the maximum stress 746MPa and 730MPa in the effective nugget part when the weld current was 8KA and 7KA, respectively. Also the some weld current of the cold rolled steel and high strength steel is applied, the fatigue life of high strength steel is obtained about four times longer than the cold rolled steel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.221-222
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• 2011

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.511-517
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• 2009

In this paper an finite element approach for the edge crack analysis of silicon-steel sheet during cold rolling is presented. Based on the damage mechanics, the proposed approach follows the analysis steps which are composed of damage initiation, damage evolution and fracture. Through those steps, we can find out the initiation instant of crack and resulting propagated length and shape of the crack. The material constants related to fracture is experimentally obtained by tension tests using standard sheet-type specimen and notched sheet-type specimen. To evaluate the prediction accuracy, we performed a pilot rolling test with a initially notched sheets. It is shown that the results obtained by the approach converged to the experimental one concerning about the direction and length of propagated crack. The capability of the proposed one is demonstrated through the application to the actual silicon-steel rolling mill.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.67-75
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• 2000

It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.665-672
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• 1997

In this paper, sixteen column specimens were tested under the concentrated and excentric load condition to examine the structural behavior of strengthened columns. 16 column specimens were divided into four groups. One group is not strengthened, the other three groups are strengthened by the materials : 1) steel plate, 2) carbon fiber sheet, and 3) glass fiber sheet, each group is composed of four specimens. As a result, strengthened columns have larger bearing capacity and energy absorption after ultimate load than unstrengthened columns. The column group strengthened with steel plate has the best bearing capacity among the strengthened column groups. Also, the columns strengthened with the carbon fiber sheet are similar to glass fiber sheet in bearing capacity. If necessary to strengthen columns in trouble, car should be taken to treat the joint between beam and column because of crack propagation in tension side.

• Journal of the Korean institute of surface engineering
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• v.29 no.3
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• pp.203-210
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• 1996

The purpose of this study is to investigate behavior of surface oxide on the cold rolled sheet used for the drum material and its phosphatability. Phosphatability is dependent of the characteristics of surface oxide on the cold-rolled sheet and can be estimated by using the electrochemical method and measuring $\tau$ value which is the time to be exposed to substrate Fe. $\tau$ value is varied with the steel composition, width direction of the sheet and SPM length. The good phosphatability and uniform surface color can be obtained by increasing SPM elongation and decreasing FCS temperature.