• Title, Summary, Keyword: Damper

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A Study on the Characteristics of an Amplitude Proportional Friction Damper (변위비례식 마찰댐퍼의 특성에 관한 연구)

  • 박동훈;최명진
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.717-720
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    • 2002
  • An Amplitude Proportional Friction Damper (APFD) system is considered in order to improve the stick-slip characteristics of Coulomb friction damper. The frictional force is proportional to the amplitude in APFD system and the system is non-linear as is Coulomb damper system. The free vibration analysis on an 1-DOF system has conducted to demonstrate the characteristics of the APFD system and the results show that the APFD system has similar damping characteristics to the viscous damper system. It is concluded that the APFD system may become a cost effective substitution for the viscous damper and it also has certain advantages over Coulomb damper system since the APFD system can be designed to work with no stick-slip.

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Performance Evaluation of Response-Dependent MR Damper (응답 의존형 MR 감쇠기의 성능 평가)

  • Lee, Sang-Hyun;Min, Kyung-Won;Youn, Kyung-Jo
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.511-518
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    • 2006
  • In this study, seismic response mitigation effect of an MR damper generating response-dependent frictional force is investigated. It has been reported in previous studies that passively operated MR damper with constant input current doesn't show better control performance than semi-active MR damper with varying input current calculated by control algorithms such as linear quadratic regulator and sliding mode control. However, in order to operate the MR damper semi-actively, other control systems besides the damper itself such as sensors for measuring structural responses and controller for calculating optimal input current are necessary, which deteriorate the economical efficiency. This study presents a MR damper generating frictional force of which magnitude is controlled in accordance to the displacement and velocity transferred to the damper. Numerical analyses results indicate that the performance of the response dependent MR damper is closely related with the range of the friction force and it can be designed to short better control performance than the passive MR damper.

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Mechanical Characteristic Analysis of Coil Spring & Viscous Damper (Coil Spring & Viscous Damper System의 동특성분석)

  • Kim, Min-Kyu;Choun, Young-Sun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.11 no.2
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    • pp.19-26
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    • 2007
  • This paper presents the results of experimental studies of the mechanical characteristics of the Coil Spring and Viscous Damper system. The Coil Spring and Viscous Damper systems were selected for the isolation of Emergency Diesel Generator (EDG) which is located in Nuclear Power Plant (NPP). The Coil Spring and Viscous Damper systems were developed for the operating vibration isolation and seismic isolation for scaled Model EDG System. The damping properties of the viscous damper changes as the variation of velocity. Through this research nonlinear damping characteristics and the effective stiffness of coil spring and viscous damper system were evaluated.

Experimental calibration of forward and inverse neural networks for rotary type magnetorheological damper

  • Bhowmik, Subrata;Weber, Felix;Hogsberg, Jan
    • Structural Engineering and Mechanics
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    • v.46 no.5
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    • pp.673-693
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    • 2013
  • This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

Design of the Spacer Damper with Automatic Clamping Device for Transmission Line (자동클램핑 장치형 Spacer Damper 설계)

  • Park, Jong-Beom;Ahn, Yong-Ho;Yoon, Gi-Gab;Kim, Kwang-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1790-1795
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    • 2000
  • The purpose of this papery is to introduce a new spacer damper's design for the bundle transmission lines network. It has the design, the main characteristics and advantage of this new kind of spacer damper. To reply to this problems, France, Japan and other countries had developed through many years a spacer damper with an automatic system. While the automatic clamping device are free of maintenance such as fatigue Break and aeolian vibration, imported price are so high. Now it is necessary to design, manufacture and certificate these automatic clamping device spacer damper.

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A Study on the Dynamic Characteristics of Free-Friction Stroke Damper by Finite Element Method (유한요소법을 이용한 Free-Friction Stroke 댐퍼의 동특성 해석)

  • Ku, Hi-Chun;Lee, Jae-Wook;Yoo, Wan-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.12
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    • pp.1417-1426
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    • 2009
  • Various types of damper are usually applied to reduce noise and vibration for mechanical systems. Especially, for washing machines, the free-friction stroke damper is installed. The behavior of the free-friction stroke damper has nonlinear characteristics such as hysteresis and viscoelastic properties because of its foam material. First of all, the dynamic experiments were carried out by using a MTS machine to find characteristics of the free-friction stroke damper. And the simulation model of the free-friction stroke damper and characteristics of a foam material were evaluated by using optimization technique. To make a good simulation model which can show the dynamic characteristics, it is important to understand the working mechanism of the damper. The Finite Element Method (FEM) technique can help us instinctively understand the damping phenomenon under operating conditions, because we can observe the condition of damper at every step in the simulation by using it. Also, by changing factors, we can comprehend the variation of characteristics of damper. So, in this paper, a study on the dynamic characteristics of free-friction stroke damper by FEM is focused on. Finally, the possibility which physical experiments can be replaced into simulations is shown.

Reliability assessment of semi-active control of structures with MR damper

  • Hadidi, Ali;Azar, Bahman Farahmand;Shirgir, Sina
    • Earthquakes and Structures
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    • v.17 no.2
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    • pp.131-141
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    • 2019
  • Structural control systems have uncertainties in their structural parameters and control devices which by using reliability analysis, uncertainty can be modeled. In this paper, reliability of controlled structures equipped with semi-active Magneto-Rheological (MR) dampers is investigated. For this purpose, at first, the effect of the structural parameters and damper parameters on the reliability of the seismic responses are evaluated. Then, the reliability of MR damper force is considered for expected levels of performance. For sensitivity analysis of the parameters exist in Bouc- Wen model for predicting the damper force, the importance vector is utilized. The improved first-order reliability method (FORM), is used to reliability analysis. As a case study, an 11-story shear building equipped with 3 MR dampers is selected and numerically obtained experimental data of a 1000 kN MR damper is assumed to study the reliability of the MR damper performance for expected levels. The results show that the standard deviation of random variables affects structural reliability as an uncertainty factor. Thus, the effect of uncertainty existed in the structural model parameters on the reliability of the structure is more than the uncertainty in the damper parameters. Also, the reliability analysis of the MR damper performance show that to achieve the highest levels of nominal capacity of the damper, the probability of failure is greatly increased. Furthermore, by using sensitivity analysis, the Bouc-Wen model parameters which have great importance in predicting damper force can be identified.

Full-scale test of dampers for stay cable vibration mitigation and improvement measures

  • Zhou, Haijun;Xiang, Ning;Huang, Xigui;Sun, Limin;Xing, Feng;Zhou, Rui
    • Structural Monitoring and Maintenance
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    • v.5 no.4
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    • pp.489-506
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    • 2018
  • This paper reported test of full-scale cables attached with four types of dampers: viscous damper, passive Magneto-Rheological (MR) damper, friction damper and High Damping Rubber (HDR) damper. The logarithmic decrements of the cable with attached dampers were calculated from free vibration time history. The efficiency ratios of the mean damping ratios of the tested four dampers to theoretical maximum damping ratio were derived, which was very important for practical damper design and parameter optimization. Non-ideal factors affecting damper performance were discussed based on the test results. The effects of concentrated mass and negative stiffness were discussed in detail and compared theoretically. Approximate formulations were derived and verified using numerical solutions. The critical values for non-dimensional concentrated mass coefficient and negative stiffness were identified. Efficiency ratios were approximately 0.6, 0.6, and 0.3 for the viscous damper, passive MR damper and HDR damper, respectively. The efficiency ratio for the friction damper was between 0-1.0. The effects of concentrated mass and negative stiffness on cable damping were positive as both could increase damping ratio; the concentrated mass was more effective than negative stiffness for higher vibration modes.

Experimental Evaluation for Structural Performance of Hybrid Damper Combining Steel Slit and Rotational Friction Damper (강재 슬릿과 회전 마찰형 감쇠 장치를 결합한 복합 감쇠 장치의 실험적 구조 성능 평가)

  • Kim, Yu-Seong;Kang, Joo-Won;Park, Byung-Tae;Lee, Joon-Ho
    • Journal of Korean Association for Spatial Structures
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    • v.19 no.3
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    • pp.101-109
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    • 2019
  • In order to develop the compatible damping device in various vibration source, a hybrid wall-type damper combining slit and friction damper in parallel was developed. Cyclic loading tests and two-story RC reinforced frame tests were performed for structural performance verification. As a result of the 5-cyclic loading test according to KBC-2016 and low displacement cyclic fatigue test, The hybrid wall type damper increased its strength and the ductility was the same as that of the slit damper. In addition, As a result of the two-layer frame test, the reinforced frame had about twice the strength of the unreinforced frame, and the story drift ratio was satisfied to Life Safety Level.

Impulse Response Analysis of an Amplitude Proportional Friction Damper System (변위비례식 마찰댐퍼 시스템의 임펄스 가진 응답해석)

  • 최명진;박동훈
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.5
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    • pp.377-384
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    • 2004
  • An Amplitude Proportional Friction Damper (APFD), in which the friction force is proportional to the system displacement, has been introduced and mathematically modeled. To understand the damping characteristics of APFD, analytical solutions for the impulse response has been derivedand compared to the viscous damper. It is found that APFD system has very similar damping characteristics to viscous damper even though it is a friction damper. APFD may be used as a cost-effective substitution for the viscous damper and could also be used to improve the simple friction or Coulomb dampersince APFD works with no stick-slip and always returns to original position when external disturbance is disappeared.