• 한국압력기기공학회 논문집
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• 제4권2호
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• pp.29-33
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• 2008

As the measures of nuclear power plant utilities and manufacturers to reduce the defects of tube expansion region during manufacturing steam generators, many types of NDEs(Non-Destructive Examinations) are conducted to inspect the expansion region. The expansion region of tube is subject to degrade because of stress concentration induced by tube expansion, sludge pile and high temperature. So the inspections for tube expansion region have been reinforced. Liquid penetrant test, helium leak test, Bobbin profile test and hydraulic test are performed to confirm the integrity of tube expanded by hydraulic expansion method. Liquid penetrant test and helium leak test are used to inspect seal weld region on tubesheet end part. Bobbin Profile test is used to inspect fully the expanded region of steam generator tube. Hydraulic test finally verifies the integrity of seal weld region on tubesheet end part.

• 한국해안·해양공학회논문집
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• 제20권2호
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• pp.184-193
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• 2008

아산호 상류지역의 도시화 진행과 이상 기후 등에 따른 강수량 증가로 아산만 방조제 배수갑문 확장의 필요성이 제기됨에 따라 배수갑문 확장으로 인한 방류량 증가가 아산만 및 주변 해역에 미치는 영향을 수리모형실험과 범용 수치모의 코드인 Delft3D, FLOW-3D를 이용하여 검토하였다. 그 결과 아산만 방조제 배수갑문확장에 의한 영향은 미흡한 것으로 확인되었다.

• Geomechanics and Engineering
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• 제25권4호
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• pp.283-294
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• 2021

This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.337-340
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• 2008

The gate expansion was planed to increase discharge capacity of gate structure at sea dike in Asan Bay. So it was estimated for changing of hydraulic states in Pyeongteak Harbor Zone caused by gate expansion, by 2D and 3D CFD Module. In result, influence of gate expansion was less than tidal current and discharge ratio between old gate and new gate was 4:6.

• 한국생산제조학회지
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• 제9권1호
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• pp.88-95
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• 2000

In this paper, an expansion-resonator type pulsation attenuator is proposed to absorb and attenuate flow an pressure ripple with high frequencies generated from hydraulic control systems. The basic principle of a pulsation attenuator proposed here is applied to propagation, reflection, absorption of pressure waves at the cross section of discontinuity and resonance in the pipeline. It has advantage of the compact size and high degree fo freedom for installation in hydraulic systems. The design scheme based on distributed parameter pipeline system with dissipative viscous compressible model is developed. To investigate the reduction of flow and pressure ripple with high frequencies produced by swash plate type axial piston pump, two kinds of attenuators are manufactured. It is experimently confirmed that the spectral intensity of flow and pressure ripple with high frequencies from the pump are reduced up to about 20$^{\circ}$~30dB by using attenuators proposed here. The calculated results were in good agreement with the measured values. From there sults of this study, it is shown that an expansion-resonator type pulsation attenuator is effective in a wide frequency ranges to attenuate the flow and pressure ripple from hydraulic components.

• 화약ㆍ발파
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• 제17권4호
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• pp.32-50
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• 1999

This study deals with interface charactristics of tube and tubesheet of the nuclear steam generator by the explosive expansion in order to take advantage of optimum expansion ratio, pull-out strength and leakage tightness and improvement of the resisitance on the stress corrosion cracking for low residual stress. The paper also show the relationship between roll, hydraulic and explosive expansion. The results obtain are as follows (1) Because of the explosive bonding is to use the high speed pressure and energy by the explosive, workability is good, bonding region is homogenous (2) Expansion ratio is 2.7%, Pull-out strength 850kg, Leakage strength $500kg/cm^2$. Clearance gap is 10~30mm in case of explosive expansion and interface structure of the tube and tubesheet is optimum condition. (3) As the transition region of the explosive expansion is inactive, the resistance of the stress corrosion cracking is increases 30~40% compare to the roll and hydraulic expansion.

• 한국지반공학회논문집
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• 제39권1호
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• pp.5-14
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• 2023

말뚝이 근입된 지반의 융기는 말뚝에 추가적인 상향 주면 마찰력을 발생시켜 말뚝의 안정성을 저해할 수 있다. 본 연구에서는 말뚝의 일부에 지반 변형에 능동적으로 대응 가능한 부재가 삽입되어 말뚝에 작용하는 상향 주면 마찰력을 감소시킬 수 있는 새로운 말뚝 기초 양식을 제안하였다. 제안된 말뚝의 실효성을 검증하기 위하여 지반 변형 대응 부재로서 유압 실린더가 적용된 말뚝을 설계 및 제작하였다. 일반 말뚝과 제안된 말뚝을 대상으로 지반 융기 모사 실험을 수행하여 선단 하중, 주면 마찰력과 지반 변형 대응 부재의 팽창량에 따른 선단 하중의 변화를 분석하였다. 실험 결과, 매우 적은 양의 실린더 부재의 팽창에도 말뚝에 작용하는 인발 마찰력이 완전히 상쇄되며 이에 따라 선단 하중이 증가하였다. 그러나 실린더 부재의 과도한 팽창은 상향 마찰력의 감소를 넘어 부주면 마찰력을 발생시키므로 지반 팽창량 및 말뚝의 허용 변위를 고려한 적절한 지반 변형 대응 부재의 팽챵량 산정이 필요하다.

• 에너지공학
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• 제22권2호
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• pp.148-155
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• 2013

한국표준형원전(OPR-1000)의 증기발생기 전열관은 관재료로 Alloy 600과 Alloy 690이 사용되고 있으며 전열관 확관방법은 폭발확관법이 적용되었다. 원전 운전경험에 따르면 전열관 확관법으로 폭발확관법이 사용된 증기발생기의 전열관들은 원주방향 균열이 잘 발생하였으며 그 위치는 전열관의 확관천이부위 외면이었고 슬러지에 의해 둘러싸인 지역이었다. 그러나 같은 조건의 전열관이라도 수압확관법이 적용된 경우는 원주방향 균열보다는 축방향 균열이 우세한 경향을 보여왔다. 따라서 본 연구에서는 상기와 같은 차이를 규명하기 위하여 전열관과 관판의 형상을 모델링하였으며 확관법에 따라 운전중 조건에서 전열관의 확관천이 부위에 작용하는 응력의 크기를 전산프로그램을 사용하여 계산하였고, 균열의 방향성과 우세성을 평가하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제2권4호
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• pp.40-46
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• 2001

Bulging is a forming method to shape die cavity by using hydraulic pressure in tube or vessel. Bulging machine and die were developed in order to produce vessel for keeping warm. Bulging machine is a double type with two horizontal cylinders for bulging of two pieces at the same time. The developed die system has one bulging die and two drawing dies for necking at both ends of the tube. The diameter of tube expands by hydraulic pressure in tube. At the same time, thrust at both ends of the tube pushes tube in the direction of expansion to obtain high expansion rate with no crack. In this study, the bulging properties were investigated to solve tube crack and necking in manufacturing vessel by combining bulging and drawing. As a result, high expanding rate of tube radius without crack, precision necking and high productivity were obtained.

• Water Engineering Research
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• 제1권1호
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• pp.63-74
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• 2000

This paper presents a two- phase search scheme for optimal pipe expansion of expansion of existing water distribution systems. In pipe network problems, link flows affect the total cost of the system because the link flows are not uniquely determined for various pipe diameters. The two-phase search scheme based on stochastic optimization scheme is suggested to determine the optimal link flows which make the optimal design of existing pipe network. A sample pipe network is employed to test the proposed method. Once the best tree network is obtained, the link flows are perturbed to find a near global optimum over the whole feasible region. It should be noted that in the perturbation stage the loop flows obtained form the sample existing network are employed as the initial loop flows of the proposed method. It has been also found that the relationship of cost-hydraulic gradient for pipe expansion of existing network affects the total cost of the sample network. The results show that the proposed method can yield a lower cost design than the conventional design method and that the proposed method can be efficiently used to design the pipe expansion of existing water distribution systems.