• 한국지반공학회논문집
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• 제37권4호
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• pp.5-17
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• 2021

본 논문은 만곡부 제방에 대해 곡률각도, 곡률반경에 따라 3차원 해석을 실시하여 침투특성을 규명하였다. 제방만곡부에서 동수경사는 2차원 해석 결과에 비해 외측제방에서는 감소하였고, 내측제방에서는 증가하였다. 곡률각도와 곡률반경이 작을수록 2차원 해석 대비 동수경사의 변화가 큰 경향을 나타내었으며, 곡률각도보다는 곡률반경이 동수경사에 미치는 영향이 큰 것으로 나타났다. 한계동수경사에 의한 파이핑 안전율 산정결과, 2차원 해석에 대비하여 안전율은 외측제방에서는 2~5%가 증가되었고, 내측제방에서는 4~12%가 감소되었다. 이 감소폭을 고려해 볼 때 제방만곡부에 대해 2차원 해석을 실시하고 파이핑에 대한 허용안전율 Fs=2.0보다 0.1~0.3정도 더 크게 설계하면 만곡부의 안전율은 약간 감소되지만 안정성 확보에는 무리가 없는 것으로 판단되었다.

• 산업기술연구
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• 제20권A호
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• pp.169-178
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• 2000

The 4-point bending tests have been performed In order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

• 한국전산유체공학회지
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• 제13권1호
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• pp.21-27
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• 2008

A numerical study for laminar flow in the entrance region of helical tubes for uniform inlet velocity conditions is carried out by means of the finite volume method to investigate the effects of Reynolds number, pitch and curvature ratio on the flow development. This results cover a curvature ratio range of 1/10$\sim$1/320, a pitch range of 0.0$\sim$3.2, and a Reynolds number range of 125$\sim$2000. It has been found that the curvature ratio does significantly effect on the angle of flow development, but the pitch and Reynolds number do not. The characteristic angle $\phi_c(=\phi/\sqrt{\delta})$, or the non-dimensional length $\overline{l}(=l\sqrt{\delta}cos(atan\lambda)/d)$ can be used to represent the flow development for uniform inlet velocity conditions. In uniform inlet velocity conditions, the growth of boundary layer delays the flow development attributed to centrifugal force, and in which conditions the amplitude of flow oscillations is smaller than that in parabolic inlet velocity conditions. If the pitch increases or if the curvature ratio or Reynolds number decreases, the minimum friction factor and the fully developed average friction factor normalized with the friction factor of a straight tube and the flow oscillations decrease.

• Journal of Mechanical Science and Technology
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• 제18권2호
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• pp.302-312
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• 2004

This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient.

• 대한토목학회논문집
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• 제33권2호
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• pp.483-493
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• 2013

콘크리트 구조물의 대형화에 따라 고강도를 갖는 재료가 최근에 많이 사용되고 있는 추세이다. 고강도 재료의 사용은 역학적 성질 또는 내구성에 있어서는 장점이 있으나 구조물의 연성 거동에는 불리한 것으로 알려져 있다. 철근콘크리트 부재는 강도뿐만 아니라 적절한 연성이 확보되도록 설계가 되어야 하기 때문에 철근콘크리트 보의 연성을 적절하게 평가할 수 있어야 한다. 본 연구에서는 고강도 재료를 사용한 철근콘크리트 보부재의 곡률연성지수의 예측식을 제시하고자 하였다. 이를 위하여 고강도 콘크리트 및 철근을 사용한 직사각형 단면 RC 보의 모멘트-곡률 관계를 해석적 방법으로 계산하여 다양한 철근 배치 조건하에서 콘크리트 및 철근의 강도가 부재의 휨거동 및 곡률연성지수에 미치는 영향을 분석하였고, 단철근 및 복철근 보에 모두 적용할 수 있는 극한상태에서의 압축철근의 응력을 고려한 새로운 곡률연성지수 예측식을 도출하였다. 제안한 곡률연성지수 예측식은 기존의 식과 비교분석하였으며, 단철근 및 복철근 보에서 예측식에 의해 계산된 곡률연성지수는 수치해석에 의해 얻은 곡률연성지수 값을 오차 범위 9% 내에서 예측하는 것으로 나타났다.

• 자동차안전학회지
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• 제3권2호
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• pp.28-33
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• 2011

This paper presents driving path estimation algorithm for adaptive cruise control system and advanced emergency braking system using multi-sensor fusion. Through data collection, yaw rate filtering based road curvature and vision sensor road curvature characteristics are analyzed. Yaw rate filtering based road curvature and vision sensor road curvature are fused into the one curvature by weighting factor which are considering characteristics of each curvature data. The proposed driving path estimation algorithm has been investigated via simulation performed on a vehicle package Carsim and Matlab/Simulink. It has been shown via simulation that the proposed driving path estimation algorithm improves primary target detection rate.

• 한국통신학회논문지
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• 제22권5호
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• pp.881-888
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• 1997

The existing method s for curvature estimation have a common problem in determining a unique smoothong factor. we previously proposed two approaches to overcome that problem: a constrained regularization approach and a mean field annealing approach. We consistently detected corners from the perprocessed smooth boundary obtained by either the constrained eglarization approach or the mean field annealing approach. Moreover, we defined corner sharpness to increase the robustness of both approaches. We evaluate the performance of those methods proposed in this paper. In addition, we show some matching results using a two-dimensional Hopfield neural network in the presence of occlusion as a demonstration of the power of our proposed methods.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.273-276
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• 2006

The focus of this study is on the enhancement of flatness for the shielded slot plate, one of main components of the MCFC stack. The shielded slot plate is to get curvature during manufacturing process since it is produced by forming operation from only one side of it. Therefore, a correction die is proposed to place just after the main die to apply unbending on the curved plate to get almost flat product. In the design for the correction die, four kinds of design factors are selected to study which factor is the most influencing one affecting the flatness of the plate. From the experimental results using Taguchi method, it has been revealed that the Young's modulus of urethane die is the most critical factor.

• 한국기계가공학회지
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• 제5권3호
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• pp.23-28
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• 2006

The focus of this study is placed on the enhancement of flatness for the shielded slot plate, one of main components of the MCFC stack. The shielded slot plate is to get curvature during manufacturing process since it is produced by forming operation from only one side of it. Therefore, a correction die is proposed to place just after the main die to apply unbending on the curved plate to get almost flat product. In the design for the correction die, four kinds of design factors are selected to study which factor is the most influencing one affecting the flatness of the plate. From the experimental results using Taguchi method, it has been revealed that the Young's modulus of urethane die is the most critical factor.

• Structural Engineering and Mechanics
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• 제66권2호
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• pp.195-201
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• 2018

From the structural safety point of view, ductility is an important parameter, a relatively high level of curvature ductility would provide to the structure an increased chance of survival against accidental impact and seismic attack. The ductility of reinforced concrete beams is very important, because it is the property that allows structures to dissipate energy in seismic zone. This paper presents a revision of an earlier formula for predicting the curvature ductility factor of unconfined HSC beams to make it simpler in the use. The new formula is compared with the earlier formula and other numerical and experimental results. The new formula regroups all parameters can affecting the curvature ductility of unconfined HSC beams and it has the same domain of application as the earlier formula.