• 대한기계학회논문집A
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• 제27권2호
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• pp.327-333
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• 2003

Most of shape defects in steel strip are originated from the structure of rolling mill itself. For instance, strip crown occurs when the work roll is deformed by the bending moment induced on roll chocks. To get rids of the shape defects, it is necessary to increase the stiffness of rolling mill. The structure change of back-up roll is one of alternative ways to increase the mill stiffness without facility revamping from 4 high mill to 6 high mill. In this research work, the new back-up roll was developed and can be used in any type of 4 high mill to reduce the strip shape defects. The developed back-up roll consists of sleeve, arbor and phase angle adjusting system for arbor. The circumference of arbor is specially machined to adapt the strip width change during rolling. The experimental cold rolling test was done to prove the effectiveness of newly developed back-up roll. The experimental rolling results show that the new back-up roll has more powerful performance in reducing the shape defects than conventional back-up roll. It was also found that the new back-up roll has higher stability for shape control. In addition to, the only sleeve surface needs to be reground and changed in most cases, so that the maintenance cost can be greatly reduced.

• 소성∙가공
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• 제16권6호
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• pp.438-442
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• 2007

Sidewall curl is the curvature that results from non-uniform through-thickness strain present in the sheet stamping process which involves material flow over a die radius. In order to understand and control curl for tight fit-up tolerances, an analytical model that can provide a reliable measure for the amount of curl would be very helpful. In this study, a model is developed based on the moment-curvature relationship during bending-under-tension operations. For the verification of analytical model, sidewall curl is experimentally measured after deformation of a strip using a bending-under-tension test system. The results show a consistent relationship between the theoretically predicted value and the experimentally obtained one, especially in regions of high curl.

• 대한조선학회논문집
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• 제49권2호
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• pp.109-115
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• 2012

Slamming phenomenon may occur when a ship navigates a high sea region, where the response of ship can be expected as elastic behaviour and the resultant wave loads may increase. In this paper, numerical analysis of ship motions and wave loads including momentum slamming was performed using the strip theory with regular waves. In order to analyze the effect of slamming force on the global ship motions, time histories of each mode of displacement and forces were simulated by using Newmark-beta time integration scheme. The added mass and damping coefficients calculated by Lewis form method were compared with the results of given references. For verification of numerical results, the motion RAOs of a S175 containership were calculated as an example of application and time histories of respective displacement and vertical bending moment were compared with the results of ITTC workshop benchmark test.

• 한국강구조학회 논문집
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• 제26권2호
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• pp.69-79
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• 2014

본 연구에서는 콘크리트 섬유보강플라스틱(FRP)로 보강된 철골보의 정적 휨하중상태에서 휨거동에 관한 실험결과를 제시하였다. 아라미드섬유 스트립과 탄소섬유 스트립으로 보강된 4개의 실험체를 제작하였으며, 1개의 기준실험체를 제작하였다. 이중 두 실험체는 부분보강방식으로 보강되었다. H빔은 두 종류의 파괴모드를 가지고 있는데, (1) 부분보강 실험체에서는 FRP 스트립이 탈락(debonding)되는 파괴모드를 보이고 있으며, 전면보강 실험체에서는 FRP 스트립이 파단(rupture)되는 거동을 보이고 있다. 실험결과 16%의 휨내력 상승효과를 관찰하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제3권2호
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• pp.199-204
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• 1999

최근에 복합재료는 콘크리트, 집성보와 같은 기존의 구조재를 보강하여 성능을 향상시킬 목적으로 적용되고 있다. 특히, 대규모의 집성보 구조물은 춤이 큰 부재를 필요로 하는데 섬유보강판을 이용하여 보의 상하부를 보강하면 춤을 크게 하지 않고도 보의 강도와 강성을 증가시킬 수 있다. 본 연구에서는 집성보에 유리섬유보강 플라스틱판(GFRP)을 붙여 스팬 중앙에 집중하중을 가한 휨실험을 수행하였고 실험결과를 층간이론을 이용한 수치해석법과 비교하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.319-320
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• 2006

• 대한조선학회논문집
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• 제41권4호
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• pp.45-52
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• 2004

Exact solution on the anti-symmetric response of ships having uniform sectional properties in waves is derived. Boundary value problem consisted of Timoshenko beam equation and free-free end condition is solved analytically. The responses are assumed as linear and wave loads are calculated by using strip method. Horizontal bending moment, shear force and torsional moment are calculated. The developed analysis model is used for the benchmark test of the numerical codes in this problem. Also the application on the preliminary design of barge-like ships and VLFS (Very Large Floating Structure) is expected

• 대한조선학회논문집
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• 제41권2호
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• pp.47-54
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• 2004

Exact solution on the vertical responses of ships having uniform sectional properties in waves is derived. Boundary value problem consisted of Timoshenko beam equation and free-free end condition is solved analytically. The responses are assumed as linear and wave loads are calculated by using strip method. Vertical bending moment, shear force and deflection are calculated. The developed analysis model is used for the benchmark test of the numerical codes in this problem. Also the application on the preliminary design of barge-like ships and VLFS (Very Large Floating Structure) is expected.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.410-415
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• 2002

A winding bend rig is designed to overcome the drawbacks of the conventional bend rig for measuring springback ratio of a strip or plate. Using the present bend rig, springback ratios are measured and they are compared with ones that obtained by using simple beam theory and tensile test. Theoretically, there should be no difference between the two values as far as the simple beam theory holds true for the bending test. But, within the scope of our tests, there is a difference of 5% between the two values since the specimen under bend test is subjected to a transverse shear force and friction force on the surface of the specimen.

• 소성∙가공
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• 제16권7호
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• pp.516-520
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• 2007

As the springback of sheet metal during unloading nay cause deviation from a desired shape, accurate prediction of springback is essential for the design of sheet stamping operations. On the removal of the applied load the specimen loses its elastic strain by contracting around the contour of the block, the radius $\rho$ can be determined by the residual differential strain. Therefore in this study the springback estimated by the residual differential strain is experimentally validated through the comparison with those obtained by U-bending test. The springback characteristics of two analytical models are also estimated at various processing conditions such as thickness, curvature of radius and drawing strain. The model based on residual differential strain has an applied transition strain where the springback undergoes a dramatic decrease. Both models show that springback decreases with increased strip thickness and with decreased radius of curvature. For no applied tension, the model based on residual differential strain predicts more springback as compared to the moment based model.