• Journal of Welding and Joining
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• 제15권2호
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• pp.54-63
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• 1997

For the purpose of establishing laser welding condition (laser power, welding speed and beam focus) and of evaluating tailored blanks for two kinds of thin steel sheets SPCC and SK5M using in the thin plate structure such as automobile, train, and so on, investigated their $CO^2$ laser weldability under various initial welding conditions. SPCC thin sheet showed good weldability under some welding conditions. But, high carbon steel sheet SK5M needed heat treatment after welding to obtain ductility of the welded joint. And next, tailored blank was tested through deep drawing to evaluate reliability of their obtained laser welding conditions. The forming depths by tailored blank were SPCC+SPCC=22-25mm and SK5M+SK5M=13-25mm.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.17-20
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• 2000

In order to improve the sheet formability of the ferritic stainless steel, the through-thickness textures of the recrystallized sample was modified by means of a thermomechanical treatment. An annealing process between the cold rolling reductions modified the preferred orientations throughout the thickness, which resulted in the modification of the final cold rolling texture as well as the final recrystallization texture. With the help of the modification of the recrystallization texture by the intermediate annealing, improvement of the sheet formability, i.e. an increase of the Lankford value.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.162-167
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• 2000

The warm deep drawability in square cup drawing is investigated about a newly developed high-strength steel sheet with retained austenite which is transformed into martensite during forming. For this investigation, six steps of temperature ranges, from room temperature to $250^{\circ}C$, and five kinds of drawing ratio, from 2.2 to 2.6 were adopted. As a result the maximum drawing force and the maximum drawing depth were affected by the elevated temperatures, and the more stable thickness strain distribution was observed to the elevated temperatures. But blue shortness happened over $200^{\circ}C$. The FEM analysis using the LS-DYNA code is adopted to compare the experimental results with the analytical results for thickness strain distribution.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.727-732
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• 1999

In this research, we made an experiment on the 10 specimen beams that we made. The specimen beams consist of 4 steel plate strengthening beams and 5 carbon fiber sheet strengthening beams. We applied the methods of notch, rounding off a edge, anchor bolt and side shear strengening to the steel plate and for the case of carbon fiber sheet, we applied the methods of anchor bolt, line anchor and shear strengthening. After all the cases were applied, the beams was measured and analyzed about the behavior property of strengthened beams, th ability of strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods resulted in almost same value until the yield load, and it wasn't quite different from the theoretical value. In comparison with existing method, the SER, SEAS for the steel plate and the CEA, CESS, CCESS for carbon fiber sheet showed the increasement of ductility with big displacement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• 한국생산제조학회지
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• 제23권4호
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• pp.350-354
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• 2014

Recently, high strength steel (HSS) sheet metal has been widely used to improve lightweight structures in the automotive industry. Because HSS sheets have high strength but low elongation, it is difficult both to make products with complex shapes and to control excessive springback. In order to reduce the springback after forming using HSS, draw beads were introduced in this study. The design variables, including the draw-bead positions and shapes, were optimized using a finite element analysis. A mold for a scanner support, which is part of an A3 printer, was designed using the proposed method and then utilized. The results from a finite element simulation and optimization were compared with the experiment results.

• 한국정밀공학회지
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• 제23권4호
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• pp.109-115
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• 2006

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$, Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.

• 소성∙가공
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• 제20권8호
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• pp.611-618
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• 2011

Flow forming is an incremental forming process in which rollers are used to form cylindrical parts with repeated turning of both roller and starting material. Both sheet and tube can be used as the starting material. The process is highly useful for producing hollow shaped parts from a tube, with the benefit of the average strain in the final shape being significantly lower than that from a sheet material. In the present study, the flow forming process was studied and optimized for producing a hollow shaped part from seamless steel tube by both experiment and numerical analysis. Upon considering the difficulty of forming seamless steel sheet, the thickness reduction was distributed over several tool paths. In the end, an optimum process condition was attained, and the experiment verified the simulation results.

• 소성∙가공
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• 제20권6호
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• pp.456-460
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• 2011

A major source of difficulty in die design for high strength steel is the high level of elastic recovery during unloading. The degree of elastic recovery is affected by factors such as material strength, bending angle, punch's corner radius and sheet thickness. Finite Element Method was used in the present work to quantitatively analyze the elastic recovery for various combinations of these parameters. In some cases elastic recovery happened in reverse direction. This phenomenon, which we call spring-go, was explained via changes in stress distribution in the panel occurring in the forming process.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권2호
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• pp.165-170
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• 2013

This paper presents the iron loss prediction of rotating electric machines taking account of the vector hysteretic properties of electrical steel sheet. The E&S vector hysteresis model is adopted to describe the vector hysteretic properties of a non-oriented electrical steel sheet, and incorporated into finite element analysis (FEA) for magnetic field analysis and iron loss prediction. A permanent magnet synchronous generator is taken as a numerical model, and the analyzed magnetic field distribution and predicted iron loss by using the proposed method is compared with those from a conventional method which employs an empirical iron loss formula with FEA based on a non-linear B-H curve. Through the comparison the effectiveness of the presented method for the iron loss prediction of the rotating machine is verified.