• Tribology and Lubricants
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• 제20권4호
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• pp.183-189
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• 2004

The floating ring seal is used in an oxidizer and a fuel pump of the turbo pump unit in the liquid rocket engine to optimize a leakage without rubbing phenomenon. The damper floating ring seal, one of the floating ring seals, is with round hole pattern surfaces. It can reduce the leakage by increased friction factor that obtained from experimental data. In this paper, the leakage test about floating ring seal and damper floating ring seal was conducted. The test result showed the leakage performance of damper floating ring seal was better than the leakage performance of floating ring seal. With the leakage test the lock-up and rotation test about seal was conducted and that position is measured. The relatively large lock-up eccentric ratio was obtained from the test result of damping floating ring seal. The attitude angle of seal increases with increasing of shaft rotation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.820-825
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• 2004

The floating ring seal is used in an oxidizer and a fuel pump of the turbo pump unit in the liquid rocket engine to optimize a leakage without rubbing phenomenon. The damper floating ring seal, one of the floating ring seals, is with round hole pattern surfaces. It can reduce the leakage by increased friction factor that obtained from experimental data. In this paper, the leakage test about floating ring seal and damper floating ring seal was conducted. The test result showed the leakage performance of damper floating ring seal was better than the leakage performance of floating ring seal. With the leakage test the lock-up and rotation test about seal was conducted and that position is measured. The relatively large lock-up eccentric ratio was obtained from the test result of damping floating ring seal. The attitude angle of seal increases with increasing of shaft rotation

• Smart Structures and Systems
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• 제20권5호
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• pp.619-636
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• 2017

Magnetorheological (MR) damper is a type of controllable device widely used in vibration mitigation. This device is highly nonlinear, and exhibits strongly hysteretic behavior that is dependent on both the motion imposed on the device and the strength of the surrounding electromagnetic field. An accurate model for understanding and predicting the nonlinear damping force of the MR damper is crucial for its control applications. The MR damper models are often identified off-line by conducting regression analysis using data collected under constant voltage. In this study, a MR damper model is integrated with a model for the power supply unit (PSU) to consider the dynamic behavior of the PSU, and then a real-time nonlinear model updating technique is proposed to accurately identify this integrated MR damper model with the efficiency that cannot be offered by off-line methods. The unscented Kalman filter is implemented as the updating algorithm on a cyber-physical model updating platform. Using this platform, the experimental study is conducted to identify MR damper models in real-time, under in-service conditions with time-varying current levels. For comparison purposes, both off-line and real-time updating methods are applied in the experimental study. The results demonstrate that all the updated models can provide good identification accuracy, but the error comparison shows the real-time updated models yield smaller relative errors than the off-line updated model. In addition, the real-time state estimates obtained during the model updating can be used as feedback for potential nonlinear control design for MR dampers.

• Earthquakes and Structures
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• 제3권6호
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• pp.821-838
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• 2012

This paper proposes a new three-layer pillar-type hysteretic damper system for residential houses. The proposed vibration control system has braces, upper and lower frames and a damper unit including hysteretic dampers. The proposed vibration control system supplements the weaknesses of the previously proposed post-tensioning vibration control system in the damping efficiency and cumbersomeness of introducing a post-tension. The structural variables employed in the damper design are the stiffness ratio ${\kappa}$, the ductility ratio ${\mu}_a$, and the ratio ${\beta}$ of the damper's shear force to the maximum resistance. The hysteretic dampers are designed so that they exhibit the targeted damping capacity at a specified response amplitude. Element tests of hysteretic dampers are carried out to examine the mechanical property and to compare its restoring-force characteristic with that of the analytical model. Analytical studies using an equivalent linearization method and time-history response analysis are performed to investigate the damping performance of the proposed vibration control system. Free vibration tests using a full-scale model are conducted in order to verify the damping capacity and reliability of the proposed vibration control system. In this paper, the damping capacity of the proposed system is estimated by the logarithmic decrement method for the response amplitudes. The accuracy of the analytical models is evaluated through the comparison of the test results with those of analytical studies.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• 한국기계가공학회지
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• 제11권6호
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• pp.9-15
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• 2012

Vibrational film has been more employed in ear-phones or small type of speakers along with a wide use of portable multi-media equipments such as MP3 and MP4. However, the current hand work production process of diaphragms is inefficient. In this study, a die-and-mold and a single production forming machine are developed, and they result in a multi-production forming machine. The multi-production forming machine consists primarily of a film feeding unit and an unwinding unit. A vacuum suction device provides the film feeding unit, while the unwinding unit is obtained using an appropriate damper. The advantage of the developed single production forming machine is shown according to a proper voice test.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.797-803
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• 2019

본 연구는 동력분산형 고속열차의 횡방향 진동을 저감하기 위하여 진행되었다. 동역학 해석을 통한 연구에서 동력분산형 고속열차 시제차량(HEMU-430X)은 고속열차에서 주로 사용되는 차륜프로파일(XP55, GV40, S1002)에 관계없이 낮은 등가답면구배에서 횡방향 진동이 커지고, 차륜 마모가 진행되어 등가답면구배가 커지면 횡진동이 감소하는 경향을 보였다. 이는 HEMU-430X에 적용된 현가장치 특성치들의 조합된 결과로 인해 등가답면구배가 낮을 때 차체와 대차가 1.4Hz의 주파수로 공진하여 차체 헌팅이 발생되기 때문이다. 고속열차의 횡방향 진동저감에 대한 해외 사례에서 요댐퍼의 유압강성(Hydraulic stiffness)을 낮추어 진동을 개선한 사례를 고찰하였다. 요댐퍼의 시리즈 강성은 유압강성과 탄성조인트의 조합인데 본 연구에서는 유압강성 조정대신 비교적 간단하게 할 수 있는 탄성조인트의 강성을 낮추어 횡방향 진동을 개선하고자 하였다. 신규 제작된 탄성조인트를 적용한 요댐퍼의 시리즈 강성은 기존 요댐퍼 대비 60% 수준으로 낮았다. 60% 수준의 시리즈 강성이 적용된 요댐퍼를 HEMU-430X의 TC~M2 3량에 설치하여 시운전 시험을 수행하였다. 시운전 시험 결과 TC를 선두로 한 하행 주행 시 TC~M1의 횡방향 진동이 개선되고, MC를 선두로 한 상행 주행 시 후미 TC차량의 횡진동이 개선되는 결과를 보였다. 본 연구의 진동저감 방안은 향후 영업운전을 위해 도입되는 EMU-250 및 EMU-320의 횡방향 진동 문제 발생 시 해결책으로 적용할 수 있다.

• 한국지진공학회논문집
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• 제11권3호
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• pp.63-72
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• 2007

비상디젤발전기는 원전의 안전성에 큰 영향을 미치는 매우 중요한 기기이다. 본 연구에서는 세 종류의 비상디젤발전기를 대상으로 가동중 진동을 계측하여 기초시스템에 따른 가동중 진동의 저감효과를 비교하였다. 대상 원전은 영광 5호기, 울진 2호기 및 울진 3호기 원전의 비상디젤발전기로 하였다. 영광 5호기와 울진 3호기의 비상디젤발전기는 동일한 종류의 비상디젤발전기로서 기초형식만 앵커볼트 고정과 스프링-댐퍼시스템을 이용한 면진으로 구분된다. 울진 2호기 비상디젤발전기는 기초부분에 seismic block을 설치하고 코일스프링을 이용하여 진동저감효과를 고려하였으므로 좋은 비교가 될 것이다. 이러한 진동계측의 목적은 기초형태에 따른 진동저감 효과를 비교해 보기 위함이다. 결과적으로 스프링-댐퍼 시스템이 진동저감과 시스템의 안정적 거동측면에서 좋은 효과를 보이고 있음을 알 수 있었다.

• 설비공학논문집
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• 제14권7호
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• pp.552-559
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• 2002

The fault detection and diagnosis (FDD) technology may be applied in order to decrease the energy consumption and the maintenance cost of the air conditioning system. In this study, rule bases and curve fitting models were used to detect faults in an air handling unit. Gradually progressed faults, such as the fan speed degradation, the coil water leakage, the humidifier nozzle clogging, the sensor degradation and the damper stoppage, were applied to the developed FBD system. Simulation results show good detections and diagnoses of these faults. Therefore, this method may be effectively used for the fault detection and diagnosis of the air handling unit.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.100-107
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• 2001

The main goals of the automotive suspension systems are to isolate roadway unevenness from the tire and to improve vehicle stability. To overcome the performance limitation of the passive systems the active systems which completely replace the passive spring and damper elements with a force generating actuator has been studied. However, application of the system has been limited because it has required a significant amount of power. Recently, alternative systems which retain passive elements but include active elements have been developed to reduce the power required. Those systems are mostly focused on the control system which compresses the spring-damper directly. In this study, a new type of power efficient control system which makes the spring-damper unit slide in side way is studied. After constructing the control system including dynamic modeling and motion control, two types of alternative control systems are compared in view of power consumption and dynamic attitudes such as roll responses as well as heave responses. Also, a half car bond graph model is developed to show clearly the significant differences in performances between two control systems.