• 한국자동차공학회논문집
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• 제15권6호
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• pp.177-182
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• 2007

In this paper, automotive hydraulic pipeline systems are modeled in which a straight blocked pipe, two pipes with sudden expansion or contraction are connected in series and terminated with a chamber. The frequency response characteristics of these composite pipeline systems are investigated experimentally. The theoretical analysis for various pipe configurations is base on transfer matrix method with frequency dependent viscous friction distributed parameter pipeline model. The gain and phase of transfer functions are included for comparison with experimental results. There is close agreement between the results of experimental and theoretical determination of pressure response in automotive hydraulic pipeline systems.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.34-37
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• 1996

The expanding method of tube to tubesheet joint part on neclear steam generators are classified into three classes of roller expanding, explosive expanding and hydraulic expanding. After the expanded Mock-Up specimen are made by the three expanding method. The general properties, microstructure/microvickers hardness, pull-out strength, hydraulic leak pressure, of tube to tubesheet joint part were inspected. and We evaluated the operation efficiency of expansion, reproduction of expanded joint about three expanding method. Through the overall evaluation of tube to tubesheet joint part, The hydraukic expanding and explosive expanding could be certificated more useful expanding method.

• Geomechanics and Engineering
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• 제13권1호
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• 터널과지하공간
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• 제8권1호
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• pp.26-36
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• 1998

To assess the groundwater flow near high-level radioactive waste repositories, it is important to understand the effect of coupling among thermal, hydraulic, and mechanical effects. In this paper, detailed mathematical approach to model the groundwater flow near the waste form surrounded by buffer, influenced by decay heat of radioactive waste along with stress change is developed. Two cases(1) before the full expansion of buffer and (2) after the full expansion of buffer are modelled. Based on the mathematical models in this paper, detailed numerical study shall be pursued later.

• 에너지공학
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• 제23권2호
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• pp.149-157
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• 2014

원자력발전소의 증기발생기 전열관은 가동 중에 다양한 형태의 부식 손상이 발생한다. 전열관의 외면에 발생하는 응력부식균열은 2차측 응력부식균열이라 불리는데 주로 전열관의 확관천이지역에서 발생한다. 그 원인은 이 지역의 기하학적 특성과 관련된 슬러지의 침적에 의한 불순물의 농축과 증기 발생기 제작과정에서 확관에 의한 잔류응력이다. 특히 잔류응력은 확관방법에 따라 방향성 및 그 크기가 달라지는데 전열관에 발생하는 균열의 방향 및 발생빈도는 이와 관련이 있다. 현장 경험에 따르면, 폭발확관된 전열관은 수압확관된 전열관에 비해 확관천이 부위에서 원주방향 균열이 잘 발생하는 것으로 나타났다. 따라서 본 연구에서는 예민화된 증기발생기 전열관에 대한 응력부식균열 시험을 통해 확관법에 따른 특정방향 균열의 발생빈도 및 균열 크기를 비교하였다. 또한 균열이 발생된 전열관의 파단면 검사를 통해 균열 양상과 수화학 환경 중의 특정 성분의 영향을 관찰하였다.

• 한국지반환경공학회 논문집
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• 제23권1호
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• pp.39-49
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• 2022

확장형 강관말뚝은 강관말뚝 내부에 확관장비를 삽입하여 강관을 확관하여 강관의 단면적을 증가시키는 공법으로 기존에 사용되는 마이크로파일과 비교하여 말뚝의 성능을 향상시킬 수 있는 공법이다. 본 연구에서는 실제 현장에서 강관의 확관이 가능한 확관장비를 개발하였다. 일련의 실내시험 및 현장시험을 통해 개발된 확관 장비의 강관 확장 성능을 확인하였다. 확관장치의 강관확관능력과 확관이 가능한 범위를 평가하기 위해 강관 확관장치의 최대압력에 대한 변형량과 확관시간을 측정한 결과, 강관두께가 얇을수록 변형량이 크게 발생하였으며 확관시간은 증가하였다. 두께 4.0mm 강관의 경우 두께 2.9mm 강관과 비교하여 변형량은 약 30% 적게 발생하였으나, 확관시간이 줄어드는 효과(약 40% 감소)를 얻을 수 있었다. 그리고 실제 지중에서 강관의 확관이 가능한지 확인하기 위해 현장 확관시험을 수행하였으며 지중에서 확관 후 확관 상태를 확인한 결과, 본 연구에서 개발한 강관 확관장치는 지중응력 조건에서도 강관 확관 성능을 발휘할 수 있음을 확인하였다. 마지막으로 확관하기 전 원상태의 강관과 확관 후 강관의 재료성능을 비교하여 확관형 강관말뚝의 역학적 안정성을 검증하였다.

• 한국안전학회지
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• 제32권4호
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• pp.46-52
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• 2017

Sediment exchange in river has been affected by artificial changes such as dredging and abnormal climate changes like intense rainfall. Over last decades in Korea, there were many constructions, restoration or rehabilitation in rivers. Therefore, deposition and erosion become more actively occurred than before, which may threaten the river safety such as flood defense. For safety's sake, the dredging of river bed, which is considered as the most typical measure, has been increased to extend hydraulic conveyance compared with previous conditions. However, since it might change the sediment mechanism, there would be another risk at which unexpected side effects such as headward erosion could be occurred. Particularly, sedimentation at abrupt expansion region is able to lead to hydraulic characteristics like water elevation in the upstream region in the beginning of dredging, which, however, has been barely studied in this field. Therefore in this study, the relationship between sediment mechanism at dredging section and hydraulic characteristics in upstream region were presented through numerical simulations in the idealized abruptly widen channel using Delft3D. The ideal channel of 2,000 m length with each side angle of 45 degrees at abruptly widen expansion region was employed to consider the sediment angle of repose. The sensitivity analysis was performed on the dimensionless factors consisted of upstream and downstream depths($h_u$, $h_d$), width($w_u$, $w_d$), water level(H), flow rate(Q) and discharge of sediment($Q_s$). And the sedimentation amount at dredging and the upstream hydraulic characteristics were investigated through that analysis. It showed that $h_d/h_u$, $H/h_u$ and $w_d/w_u$ were more influential in sequence of effect on sedimentation amount, while $h_d/h_u$, $w_d/w_u$ and $H/h_u$ on upstream region. It means that $h_d/h_u$ was revealed as the most significant factors on sedimentation, also it would most highly affect the rising of water level upstream.

• Geomechanics and Engineering
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• 제22권4호
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• pp.329-337
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• 2020

Polyacrylamide (PAM) possesses high water absorption capacity and a unique pH-dependent behavior that confer large potential to enhance the engineering performance of clays. In this study, calcium bentonite was treated with a nonionic PAM. Flexible-wall permeability test and the consolidation test were performed at different pH values to evaluate the effects of PAM treatment on the hydraulic and consolidation properties. Test results demonstrate that index properties are affected by the adsorbed PAM on clay surface: a decrease in specific gravity, a decrease in net zeta potential, and an increase in liquid limit are observed due to the PAM treatment. At a given pH, the compressibility of the treated clay is greater than that of the untreated clay. However, the compression indices of untreated and treated clays can be expressed as a single function of the initial void ratio, regardless of pH. Hydraulic conductivity is reduced by PAM treatment about 5 times at both neutral and alkaline pH conditions under similar void ratios, because of the reduction in size of the water flow channel by PAM expansion. However, at acidic pH, the hydraulic conductivity of the treated clay is slightly higher than the untreated clay. This reflects that the treated bentonite with PAM can be beneficially used in barrier system for highly alkaline residues.

• 비파괴검사학회지
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• 제26권3호
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• pp.174-180
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• 2006

Steam generator (SG) tubes are expanded inside tubesheet holes by using explosive or hydraulic methods to be fixed in a tubesheet. In the tube expansion process, it is important to minimize the crevice gap between expanded tube and tube sheet. In this paper, absolute and differential signals are computed by a numerical method for several different locations of tube expansion inside and outside a tubesheet and signal variations due to tubesheet, tube expansion and operating frequencies are observed. Results show that low frequency is good for detecting tubesheet location in both types of signals and high frequency is suitable for sizing of tube diameter as well as the detection of transition region. Also learned is that the absolute signal is good for measuring tube diameter, while the differential signal is good for locating the top of tubesheet and both ends of the transition region. In the case of mingled anomaly with tube expansion and tubesheet, low frequency inspection is found to be useful to analyze the mixed signal.

• 한국정밀공학회지
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• 제16권7호
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• pp.24-31
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• 1999

Bulging is a forming method to shape of 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 the both ends of tube. The diameter of tube expands by hydraulic pressure in tube. at the same time, thrust at the both ends of tube. pushes tube in the direction of expansion to obtain high expanding rate with no crack. In this study, the bulging properties were investigated to solve tube crack and necking in manufacturing vessel by the combination method of bulging and drawing. As a result, high expanding rate of tube radius without crack, precision necking and high productivity were obtained.