• Title/Summary/Keyword: Damping System

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A Study on the Wave Drift Damping of a Moored Ship in Waves (파랑중 계류된 선박의 표류감쇠에 관한 연구)

  • 이호영;박홍식;신현경
    • Journal of Ocean Engineering and Technology
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    • v.14 no.4
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    • pp.17-22
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    • 2000
  • As the offshore oil fields are moved to the deep ocean, the oil production system of FPSO(Floating Production Storage and Offloading System) Type are constructed frequently these days. So, it is very important to estimate the drift motion and damping effects due to the drift motion simultaneously. The components of slow drift motion damping consist of viscous, wave radiation effect and wave drift damping. It is needed to estimate the wave drift damping more accurately than others. The wave drift damping signifies the time-rate of mean wave drift force on oscillating ship or ocean structure which constant speed. In order to calculate this, the 3-Dimensional panel method is employed with the translating and pulsating Green function in the frequency domain. The calculation is carried out for a Series 60 ($C_B$/=0.7) and the results are compared with other numerical ones.

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A study on the improvement of a suspension system adopting a semiactive on-off damper (반능동 단속형 감쇠기를 이용한 현가장치 개선에 관한 연구)

  • 최성배;박윤식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.5
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    • pp.959-967
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    • 1988
  • In this paper, 2-DOF vehicle suspension system with a semiactive on-off damper was studied for improving the ride comfort. It is known that a nonlinear hydraulic damper, which generates force proportional to the square of the relative velocity, can describe the actual fluid resisting type damper more properly than the traditional viscous damping model. On the other hand, hydraulic damper adoption in analysis makes the system nonlinear and causes difficulties to get the system response. In this work, time domain direct integration method was used to calculate system displacement and acceleration. first of all, the response of the suspension system experiencing a given road profile was optimized by Lagrangian multiplier method within the range of given damping coefficients. The appropriate on-loaf damping values were obtained by averaging the already calculated optimum damping coefficients from Lagrangian techniques. The criterion to control the on-off mechanism was determined by examining the suspension efficiency. It was found that the best out of practically applicable criteria is following the sign (positive and negative) of the multiplication of relative displacement and velocity. Judging from the theoretical calculations, it was proved that the semiactive on-off damper can increase suspension efficiency as much as 8-11% in object function.

High-Performance Damping Device for Suppressing Vibration of Stay Cable (사장 케이블 제진을 위한 고성능 감쇠 장치)

  • Jung Hyung-Jo;Park Chul-Min;Jang Ji-Eun;Park Kyu-Sik;Lee In-Won
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.489-496
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    • 2005
  • In this paper, the feasibility of the high-performance damping device vibration suppression of stay cables has been investigated. The proposed damping system consists of a linear viscous damper and a scissor-jack-type toggle linkage. Since the mechanism of the scissor-jack-type toggle linkage amplifies the relative displacement of the linear viscous damper, it is expected that the capacity of the viscous damper used in the scissor-jack-damper energy dissipation system can be reduced without the loss of the control performance. Numerical simulation results demonstrate the efficacy of the damping system employing the scissor-jack-type toggle linkage. Therefore, the proposed damping system could be considered as one of the promising candidates for suppressing vibration of stay cable.

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Impact Analysis For a 2-DOF Shock Absorbing System with Multi-Step Damping Coefficient (다단계 감쇠계수를 갖는 2자유도계 충격흡수장치의 충격해석)

  • 김성윤;심재준;한동섭;안성찬;한근조;안찬우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.871-874
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    • 2002
  • Many malfunctions take place in container crane spreader due to impact. So we designed a 2DOF hydraulic impact absorbing system with multi-step damping coefficient and studied the effect of orifice's interval and damping coefficient. The damping coefficient of upper piston was found to be 180 N.s/m, and the orifice's interval to be 9mm, the max reaction force and the average reaction force might be lowest. Compared with a general 2-DOF impact absorbing system, the max reaction force reduced by 46%., and average reaction force reduced by 5%.

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A study on identification of the damping ratio in a railway catenary system (철도 가선시스템의 감쇄 특성 파악에 관한 연구)

  • Park Sungyong;Jeon Byunguk;Lee Eungshin;Cho Yonghyeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2005.06a
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    • pp.529-533
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    • 2005
  • A railway catenary system which supplies a train with electric power is an important system in determining the maximum speed of an electric train. However, a pantograph could be separated from a contact wire because of reciprocal action between a pantograph with constant upward force and a catenary system. The contact loss of a pantograph-catenary system is mainly affected by the dynamic characteristics of damping and wave propagation velocity of contact wire. For increasing speed of an electrical train, it is necessary to establish the techniques to identify the modal parameter of a catenary system through experiment. However, it is difficult to decouple each mode and to extract respect ive damping rat io since a catenary system has an extremely high modal density. For this reason, mode decoupling process to identify modal parameters is a principal technique in analyzing a catenary system. In this paper, the damping extract ion method for a catenary system using the continuous wavelet transform is discussed.

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Concept Design of a Parallel-type Tuned Mass Damper - Tuned Sloshing Damper System for Building Motion Control in Wind

  • Lee, Chien-Shen;Love, J. Shayne;Haskett, Trevor C.;Robinson, Jamieson K.
    • International Journal of High-Rise Buildings
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    • v.10 no.2
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    • pp.93-97
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    • 2021
  • Supplementary damping systems, such as tuned mass dampers (TMDs) and tuned sloshing dampers (TSDs) - also known as tuned liquid dampers (TLDs) - have been successfully employed to reduce building motion during wind events. A design of a damping system consisting of a TMD and two TSDs performing in unison has been developed for a tall building in Taiwan to reduce wind-induced motion. The architecturally exposed TMD will also be featured as a tourist attraction. The dual-purpose TSD tanks will perform as fire suppression water storage tanks. Linearized equivalent mechanical TSD and TMD models are coupled to the structure to simulate the multi-degree of freedom system response. Frequency response curves for the structure with and without the damping system are created to evaluate the performance of the damping system. The performance of the combined TMD-TSD system is evaluated against a conventional TMD system by computing the effective damping produced by each system. The proposed system is found to have superior performance in acceleration reduction. The combined TMD-TSD system is an effective and affordable means to reduce the wind-induced resonant response of tall buildings.

Performance verification of Smart Complex Damping System for Suppressing Vibration of Stay Cable (케이블 진동 저감을 위한 스마트 복합 감쇠 시스템의 성능평가)

  • Park, Chul-Min;Jung, Hyung-Jo;Ko, Man-Gi;Lee, In-Won
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2006.03a
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    • pp.453-460
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    • 2006
  • Stay cables, such as used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Recently some studies have shown that active and semiactive control system using MR damper can potentially achieve both higher performance levels than passive control system and adaptability with few of the detractions. However, a control system including a power supply, controller, and sensors is required to maximize the performance of the MR damper and this complicated control system is not effective to most of large civil structures. This paper proposes a smart complex damping system which consists of toggle system and MR dampers by introducing electromagnetic induction(EMI) system as an external power source to MR damper. The performance of the proposed damping device has been compared with that of the passive-type control systems employing a MR damper, a linear viscous damper, and EMI system.

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Vibration Control of Stay Cable Using Smart Passive Damping System (스마트 수동 감쇠 시스템을 이용한 사장 케이블의 진동 제어)

  • Jung Hyung-Jo;Cho Sang-Won;Jang Ji-Eun;Lee In-Won
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.497-504
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    • 2005
  • Stay cables, such as are used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Several methods have been proposed and implemented to mitigate this problem, though each has its limitations. Recently some studies have shown that active and semiactive control system using MR (Magnetorheological) damper can potentially achieve both higher performance levels than passive control system and adaptability with few of the detractions. However, a control system including a power supply, controller, and sensors is required to maximize the performance of the MR damper and this complicated control system is not effective to most of large civil structures. This paper proposes a smart passive damping system using MR dampers by introducing electromagnetic induction (EMI) system as an external power source to MR damper and verified the performance of smart passive damping system for mitigating the vibration of stay cables. The performances of smart passive damping system are compared with those of linear viscous damper and passive-mode MR damper.

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Development of a Wave Absorbing System Using a Liquefied Sandbed

  • Kang, Yoon-Koo;Takahashi, Shigeo
    • Journal of Ocean Engineering and Technology
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    • v.20 no.4 s.71
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    • pp.9-16
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    • 2006
  • A new wave-absorbing system, called the liquefied sandbed wave barrier (LSWB) system, is currently under development at the Port and Airport Research Institute (PARI) of Japan. The wave damping effect by the LSWB system is substantial, as confirmed by small-scale experiments and FEM numerical calculations, i.e., the wave transmission coefficient of the system is less than 0.2. Here, the results of large-scale experiments arediscussed in view of practical application. Although the LSWB system provides high wave damping, nearly equal to theoretical values, difficulty exists in obtaining a homogeneously liquefied sandbed, due to the occurrence of liquefied sandbed compaction by cyclic wave loading, which in turn, reduces excess pare pressure and the wave damping effect. These two phenomena primarily occur when the sandbed is composed of fine sand with small permeability. Based on experimental results, we propose a design method that includes countermeasures against such problems, and a prototype LSWB system is constructed in a very large wave flume at PARI. Wave damping by the prototype LSWB system is confirmed to be quite stable and high, as predicted by theoretical calculations.

Application of Fe-Mn High Damping Alloys for Reduction of Noise and Vibration in Power Plants (Fe-Mn 방진합금을 적용한 발전소 격납용기 살수펌프의 소음$\cdot$진동 저감효과에 관한 연구)

  • 백승한
    • Journal of KSNVE
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    • v.9 no.4
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    • pp.720-729
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    • 1999
  • Coventional methods for reducing vibration in engineering designs (i.e. by stifferning or detuning) may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Some alloys with a combination of high damping capacity and good mechanical properties can provide attractive techanical and economical solutions to problems involving seismic, shock and vibration isolation. Although several non ferrous damping alloys have been developed, none of those materials are applied in any industrial factor due largely to high production cost. To meet these requirement, we have developed a new Fe-Mn high damping alloy. In previous studies, we have reported that an Fe-17%Mn alloy exhibits the highest damping capacity(Specific Damping Capacity:SDC, 30%) among Fe-Mn binary system, and proposed that the boundaries of various types such as $\varepsilon$-martensite variant boundaries, stacking faults in $\varepsilon$-martensite, stacking faults in austenitic and ${\gamma}$$\gamma /\varepsilon$ interfaces give rise to a high damping capacity. The Fe-17%Mn alloy also has advantages of good mechanical properties(T.S. 70 kg/nm$^2$ and low cost over other damping alloys(1/4 times the cost of non-ferrous damping alloy). Thus, the Fe-17%Mn high damping alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components. In this paper, the overall properties of the Fe-17%Mn high damping alloy is introduced, and its applicability to containment spray pump in the power plant is discussed.

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