• Title/Summary/Keyword: viscous friction

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Approximate solution for a building installed with a friction damper : revisited and new result (마찰감쇠기가 설치된 건물 응답의 근사해 : 재 고찰 및 새로운 결과)

  • Min, Kyung-Won;Seong, Ji-Young;Lee, Sung-Kyung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.10a
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    • pp.850-854
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    • 2009
  • Approximate analysis for a building installed with a friction damper is revisited to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor (DMF) for the building with combined viscous and friction damping. It is found out that DMF is dependent on friction force ratio and resonance frequency. Linear transfer function from input external force to output building displacement is obtained by simplifying DMF equation. Root mean square of building displacement is derived under earthquake-like random excitation. Finally, design of friction damper is proposed by processing target control ratio, damping ratio factor, and friction force in sequence.

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Optimal design of tuned mass damper considering the friction between the moving mass and the rail (레일의 운동마찰력을 고려한 TMD 최적 설계)

  • Lee, Sang-Hyun;Woo, Sung-Sik;Cho, Seung-Ho;Chung, Lan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.582-587
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    • 2007
  • In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

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Optimal Design of Tuned Mass Damper Considering the Friction between the Moving Mass and the Rail (레일의 운동마찰력을 고려한 TMD 최적 설계)

  • Lee, Sang-Hyun;Woo, Sung-Sik;Cho, Seung-Ho;Chung, Lan
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.6 s.123
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    • pp.553-559
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    • 2007
  • In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

Precision Stabilization Control of Servo-system by Using Friction Compensation (마찰보상을 통한 서어보제어계의 정밀 안정화 제어)

  • Kang, Min-Sig
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.3 s.96
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    • pp.109-115
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    • 1999
  • This paper presents a stabilization control designed to improve position stabilization performance of a position servo-system(turret) mounted on a manuvering platform(vehicle). In the consideration of the motion of the platform, a dynamic model of the stabilization system is derived and shows the viscous and stick-slip friction torques are the major source of stabilization errors. An extended generalized minimum variance control which consists of a feedforward disturbance compensation as well as a pole placement feedback control is suggested to reduce the stabilization errors caused from the friction disturbances. This modeling and control are applied to a small experimental set-up and the experimental results confirm the accuracy of the model and the effectiveness of the suggested control.

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Surface Texturing in Hydraulic Machine Components for Friction Reduction (Surface Texturing에 의한 유압부품의 마찰저감)

  • Park, Tae Jo;Kim, Min Gyu
    • Journal of Drive and Control
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    • v.13 no.1
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    • pp.27-33
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    • 2016
  • In hydraulic machinery, the hydraulic fluid acts primarily as working fluid and secondarily as a lubricant. Hence, the viscous friction force acting on the sliding components should be reduced to improve the mechanical efficiency. It is now well known that the surface texturing is a useful method for friction reduction. In this study, using a commercial computational fluid dynamics (CFD) code, FLUENT, the lubrication characteristics of a surface textured slider bearing under high boundary pressure difference is studied. The streamlines, velocity profiles, pressure distributions, load capacity, friction force and leakage flowrate are highly affected by the film thickness ratio and the textured region. Partial texturing at the inlet region of the inclined slider bearing can reduce both friction force and leakage flowrate than in the untextured case. The present results can be used to improve the lubrication characteristics of hydraulic machinery.

The study on the measurement for the pressure drop and friction factor of corrugated metal pipes (주름관에서의 압력강하와 마찰손실 계측에 관한 연구)

  • Yun, Young-Sun;Kang, Jun-One;Yoo, Jai-Suk;Kim, Hyung-Jung
    • Journal of the Korean Society of Visualization
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    • v.4 no.2
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    • pp.76-80
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    • 2006
  • The data for friction factor of the pipe correlated by Reynolds number and relative roughness have been reported well as a Moody chart. However, the results for corrugated shapes have been not investigated sufficiently. In this research, therefore, the pressure drop and friction factor are obtained. Flexible metal tubes with corrugations for the measurement are made of stainless steel plates. The kinds of tubes for the measurement are 5 annular types and helical types. The pressure drop & the velocity of the flow are obtained by micromanometer & digital pressure sensor, supplying dry air at several steps. Then the pressure drop is calculated for each tube, using the obtained data. The result shows that the pressure drop is strongly influenced by the viscous dissipation of kinetic energy due to the circulation of flows, rather than a viscous friction loss. The pressure drop increased consistently as the Reynolds number increases.

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Estimation of viscous and Coulomb damping from free-vibration data by a least-squares curve-fitting analysis

  • Slemp, Wesley C.H.;Hallauer, William L. Jr.;Kapania, Rakesh K.
    • Smart Structures and Systems
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    • v.4 no.3
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    • pp.279-290
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    • 2008
  • The modeling and parameter estimation of a damped one-degree-of-freedom mass-spring system is examined. This paper presents a method for estimating the system parameters (damping coefficients and natural frequency) from measured free-vibration motion of a system that is modeled to include both subcritical viscous damping and kinetic Coulomb friction. The method applies a commercially available least-squares curve-fitting software function to fit the known solution of the equations of motion to the measured response. The method was tested through numerical simulation, and it was applied to experimental data collected from a laboratory mass-spring apparatus. The mass of this apparatus translates on linear bearings, which are the primary source of light inherent damping. Results indicate that the curve-fitting method is effective and accurate for both perfect and noisy measurements from a lightly damped mass-spring system.

A NOTE ON THE UNSTEADY FLOW OF DUSTY VISCOUS FLUID BETWEEN TWO PARALLEL PLATES

  • AJADI SURAJU OLUSEGUN
    • Journal of applied mathematics & informatics
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    • v.18 no.1_2
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    • pp.393-403
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    • 2005
  • We study the isothermal flow of a dusty viscous incompressible conducting fluid between two types of boundary motions- oscillatory and non-oscillatory, under the influence of gravitational force. Within the frame work of some physically realistic approximations and suitable boundary conditions, closed form solutions were obtained for the velocity profiles and the skin friction of the particulate flow. These results show that for a constant pressure gradient, only the velocity profile of the fluid and the skin friction are unaffected by gravity, while magnetic field is seen to affect both the fluid, particle velocities and the skin friction. Thus, our results are extension of previous results in literature, and graphical demonstration of some these solutions have been presented.

A Study on Acting Forces on the Vane of Vane Pump used for Vehicles′ Hydraulic Power Steering (차량용 HPS 베인펌프의 베인의 작용력에 관한 연구)

  • 정석훈;오석형
    • Tribology and Lubricants
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    • v.20 no.3
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    • pp.163-167
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    • 2004
  • Reducing friction torque of the oil hydraulic vane pump used as the power source of power steering system should consider friction torque including viscous and mechanical friction torque according to the changes of rpm and pressure. This paper analyzes the forces acting on the vane to reduce the friction torque of the vane of the hydraulic vane pump used for Hydraulic Power Steering(HPS) system, and futhermore, the forces according to the shapes of cam profiles are analyzed.

Development of Seismic Retrofit Devices for Building Structures

  • Kim, Jinkoo
    • International Journal of High-Rise Buildings
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    • v.8 no.3
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    • pp.221-227
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    • 2019
  • In this paper passive seismic retrofit devices for building structures developed by the author in recent years are introduced. The proposed damping devices were developed by slightly modifying the configuration of conventional devices and enhancing their effectiveness. First a seismic retrofit system consisting of a pin-jointed steel frame and rotational friction dampers installed at each corner of the steel frame was developed. Then two types of steel slit dampers were developed; box-type slit damper and multi-slit damper. In addition, hybrid dampers were developed by combining a slit damper and a friction damper connected in parallel. Finally a self-centering system was developed by using preloaded tendons and viscous dampers connected in series. For each retrofit system developed, an appropriate analytical model was developed, and the seismic performance was verified by loading test and earthquake analysis of case study structures. The experimental and analysis results show that the proposed systems can be used efficiently to enhance the seismic performance of building structures.