• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.549-556
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• 2002

Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins and jetty). It can also be used to isolate contaminated material from harbor, detention basin dredging, and to use this unit as dikes for reclamation work. Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. The stability analysis of geotextile tube is composed geotechnical and hydrodynamic analysis. The stability check points are sliding failure, overturning, bearing capacity failure against the wave attack. In this paper presented the construction procedure and in-situ measurement(properties of filling material, effective height variation, stress variation at geotextile tube bottom) of geotextile tube at Young-Jin Bay and stability analysis by theoretical method and hydraulic model tests

• 한국기계기술학회지
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• 제20권6호
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• pp.929-935
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• 2018

This paper develops a flow control block for a hydraulic system of a tunnel boring machine. The flow control block is a necessary component to ensure stability in the operation of the hydraulic system. In order to know the pressure distribution of the flow control block, the flow analysis was performed using the ANSYS-CFX. It was confirmed that the pressure and flow rate were normally supplied to the hydraulic system even if one of the four ports of the flow control block was not operated. In order to evaluate the structural stability of the flow control block, structural analysis was performed using the ANSYS WORKBENCH. As a result, the safety factor of the flow control block is 1.54 and the structural stability is secured.

• 대한기계학회논문집
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• 제19권6호
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• pp.1469-1478
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• 1995

PWM control is a kind of nonlinear control. The merits of PWM control of hydraulic equipment are the robustness of the high speed on-off valve and its low price. And it is easily implemented to hydraulic equipments with microcomputer. The high speed on-off valve is directly digitally controlled without any D/A converter. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using high speed on-off valve, and to give a criterion for the stability of this system. To do this, the nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are examined theoretically and experimentally. Consequently, the availability of the proposed method is confirmed well.

• 한국환경복원기술학회지
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• 제16권4호
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• pp.15-26
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• 2013

In recent years, river maintenance projects using natural methods have been continuously implemented in urban areas and methods emphasizing ecology are being developed and constructed in revetment areas. However, there is insufficient technical review on the hydraulic stability of those revetment methods during the event of flood. Therefore, a hydraulic analysis is necessary for the stream where revetments are applied. This study was conducted to develop an objective test method for the hydraulic stability of green revetment media. For this purpose, hydraulic model tests were performed for the green base materials for revetments. Tests were conducted using experimental devices for the hydraulic model which were installed to simulate the rapid current during the flood. Loss of soil by the hydraulic condition was compared and analyzed with that of dry green revetment media, and the evaluations were made on the corrosion resistance, tractive force, and contractile force. Test results showed that green revetment media had higher corrosion resistance in non-vegetation condition compared to dry green revetment media, and the loss of base materials by the rooting of vegetation showed significant reduction by the vegetation. In addition, results of the allowable tractive force of the base material indicated it is relatively stable in vegetation condition but scouring can occur in non-vegetation condition. Therefore, the development of vegetation in revetment areas is anticipated to be effective for the stability of revetment areas by reducing external forces interacting with the corrosion resistance and stream bank. The green revetment media in expected to contribute to the stability of revetment areas.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1999년도 추계학술대회논문집
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• pp.371-374
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• 1999

This paper present the nonlinear control and the Lyapunov analysis of the nonlinear electro-hydraulic system for steering control of UCT. Electro-hydraulic system itself has the high nonlinearities arisen from the nonlinear characteristics of the pressure-fluid flow in valve and friction in cylinder. These nonlinearities are unmodeled terms in the transfer function. This paper presents the system modeling, analysis of stability based on the Lyapunov function and simulation of the nonlinear hydraulic servo system.

• Tribology and Lubricants
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• 제20권1호
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• pp.33-40
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• 2004

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper, show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required propertied and performances were discussed.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.661-667
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• 2020

The optimal shape modeling of core parts through 3D modeling and structural analysis for the development of small and medium-sized ships. The goal is to improve the efficient structure of the hydraulic system for controlling the rudder among the core steering parts in small and medium-sized ships. Through 3D modeling and structural analysis, a new concept of tiller parts and a double-acting hydraulic cylinder control system were proposed and operational structural stability was evaluated. Structural analysis of the three different tiller designs that can be replaceable onto existing fishing vessels was conducted to derive the final shapes. The emphasis was placed on evaluating the structural stability of the key drive components, the tiller, pin, and cylinder rodin the maximum torque condition of the hydraulic cylinder.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.91-101
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• 2010

Based on the one-dimensional stability analysis, the self-excited oscillation in hydraulic power generating systems was studied by a simple experiment and numerical simulation. It was shown that a cavity in a conical diffuser can cause surge. With the diffuser, a high amplitude and low frequency oscillation occurs at low cavitation number. This oscillation was not observed with the straight pipe. It was confirmed that the diffuser effect of the draft tube can be the cause of the full load surge in hydraulic power system. Numerical results were also analyzed to check the validity of the one-dimensional stability analysis.

• 한국지반공학회논문집
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• 제18권5호
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• pp.251-260
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• 2002

지오텍스타일 튜브공법은 고강도 토목섬유인 지오텍스타일을 튜브모양으로 봉합하여 수리학적 방법이나 기계적인 방법으로 내부에 토사를 채워 구조물을 형성하는 공법으로, 지오텍스타일 튜브구조물은 지오텍스타일에 구속된 토사 체로 구성되며, 지오텍스타일과 토사의 복합거동 특성을 나타낸다. 또한, 구조물의 활용분야가 해안 및 호안 침식방지 구조물이나 방파제, 제방 등에 적용되어지므로 설계 및 안정해석 시, 지반공학적 검토와 파도에 의한 수리동역학적 검토가 필요하다. 본 연구에서는 지오텍스타일 튜브의 효율적인 안정해석방법에 대하여 분석하기 위하여, 방파제 (Breakwater), 이안제(Detached breakwater), 돌제(Groin)등과 같은 해안구조물의 경험 및 2차원 평형해석방법을 검토 및 적용하였으며, 해석결과의 실험적 분석을 위하여 이안제형태의 지오텍스타일 튜브에 대한 수리모형시험을 실시하였다. 본 연구에서 수행한 경험식 및 2차원 평형해석 분석은 기존의 수리모형시험을 통하여 도출된 경험식과 파도의 작용을 외력으로 한 2차원 평형해석이론을 적용.검토하였다. 또한, 수리모형시험을 통한 안정해석은 지오텍스타일 튜브의 형태(채움비율 변화), 유의파고(Significant wave height), 천단고(구조물 상부수심)의 확보유무 등의 해석변수조건을 적용하였다. 2차원 평형해석에 의한 지오텍스타일 튜브의 안정해석결과, 활동 및 전도에 대한 안정성은 튜브형태, 접지면적, 유의파고, 투영면적 등의 복합상관관계로 비선형적인 변화를 나타내었으며, 수리모형시험을 통한 안정성 검토결과, 경험식 및 2차원 평형해석결과와 근접한 결과를 나타내었다.

• 한국습지학회지
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• 제15권1호
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• pp.91-103
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• 2013

본 연구에서는 자연친화적인 호안 블록의 현장 적용시 충분한 기술적인 검증과 구조적, 수리학적 안정성 검토 등이 제대로 이루어지지 않고 있는 문제점을 개선하기 위해 생태적 기능을 확보할 수 있는 식생강화를 위한 다공성 소일 블록에 대하여 수리적 거동 변화에 따른 수리학적 안정성을 검토하였다. 대상구간을 선정하여 수치해석 및 수리모형실험을 실시하였으며 수치해석을 위해 1차원 수치해석모형인 HEC-RAS와 2차원 수치해석모형인 RMA-2를 이용하여 1, 2차원 수치해석을 실시하였고, Froude 상사법칙을 적용하여 식생 유, 무에 따른 축척된 수리모형실험을 실시하였다. 수리모형실험의 경우 실험결과에 대한 타당성을 위해 축척된 수리모형실험의 유속 및 소류력 결과를 원형으로 환산하여 1, 2차원 수치해석결과와 동일한 조건하에 비교 검토하였고 그 결과 비교적 일치된 결과가 나타난 것으로 확인되었으며 이에 따른 원형으로 환산된 소류력 결과를 기존 연구결과인 호안의 허용소류력과 비교함으로써 블록의 수리학적 안정성을 제시하였다.