• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.223-229
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• 2016

This study proposes a new technology for a smart damper with flag-shaped behavior using the combination of magnetic friction and rubber springs. The magnet provides friction and, thus, energy dissipation, and the rubber springs with precompression contribute to present self-centering capacity of the damper. To verify their performance, this study conducts dynamic tests of magnet frictional dampers and precompressed rubber springs. For the purpose, hexahedron Neodymium (NdFeB) magnets and polyurethane rubber cylinders are used. In the dynamic tests, loading frequency varies from 0.1 to 2.0 Hz. The magnets provide almost perfect rectangular behavior in force-deformation curve. The rubber springs are tested without or with precompression. The rubber springs show larger rigid force with increasing precompression. Lastly, this study discusses combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine the magnets and the rubber springs to obtain the flag-shaped behavior.

• Ocean Systems Engineering
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• v.9 no.4
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• pp.369-390
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• 2019

Herein, we present numerical simulation based model to study the use of a 'Tuned Mass Damper (TMD)' - particularly spring mass systems - to control the displacements at the deck level under seismic and ice loads for an offshore jacket structure. Jacket is a fixed structure and seismic loads can cause it to vibrate in the horizontal directions. These motions can disintegrate the structure and lead to potential failures causing extensive damage including environmental hazards and risking the lives of workers on the jacket. Hence, it is important to control the motion of jacket because of earthquake and ice loads. We analyze an offshore jacket platform with a tuned mass damper under the earthquake and ice loads and explore different locations to place the TMD. Through, selected parametric variations a suitable location for the placement of TMD for the jacket structure is arrived and this implies the design applicability of the present research. The ANSYS^*TM mechanical APDL software has been used for the numerical modeling and analysis of the jacket structure. The dynamic response is obtained under dynamic seismic and ice loadings, and the model is attached with a TMD. Parameters of the TMD are studied based on the 'Principle of Absorption (PoA)' to reduce the displacement of the deck level in the jacket structure. Finally, in our results, the proper mass ratio and damping ratios are obtained for various earthquake and ice loads.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.12-19
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• 2010

The characteristics of the torsional systems are generally examined with the nonlinearities such as the several staged clutch damper springs, gear backlashes and drag torques. Generally speaking, the system's characteristics can be found out by the eigensolutions which can show the system natural frequencies and the mode shapes. However, these factors can not give the complete solutions to avoid the noise and vibration problems related to the nonlinear effects. Therefore, several assumptions should be made for solving the real physical system problems under the linear analysis which can reflect the nonlinear effects in the torsional system. This means that the several modified linear factors such as the modified clutch damper spring constants can be used to examine and avoid the natural frequency zones related to the noise and vibration problems. Under the linear analysis with the assumed and modified values, the system can be investigated with the more reliable ways for the realistic phenomena.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.82-88
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• 2016

This paper proposes a new type of semi-active direct-drive valve(DDV) car suspension system using piezoelectric actuator associated with displacement amplifier. As a first step, controllable piezoelectric DDV damper is designed and governing equation of a quarter-vehicle suspension system consisting of sprung mass, spring, tire and the piezostack DDV damper is constructed. After deriving the equations of the motion, in order to control spool displacement and damping force the skyhook controller is designed and applied. The performance evaluation of the proposed semi-active suspension system is conducted with different displacement of spool. Then, the ride comfort analysis is undertaken in time domain with bump road profile.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.9-21
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• 2003

This paper describes the practical implementation of a semiactive hydropneumatic suspension system to provide the high off-road performance of military tracked vehicles. Real gas behavior of a spring system, frictional forces of joints, and the dynamics of a continuously variable damper are considered. The control system is consisted of two control loops, an outer loop calculates a target spool position which can deliver the required damping force and an inner loop tracks the required spool position. Dynamic tests of the one axis model show that the semiactive suspension system considerably reduces the acceleration as well as velocity and displacement of the sprung mass than the passive one.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.764-771
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• 2005

This study investigates the 3-axis transmissibility of the vehicle compact disk player's mainbase which is supported by dampers and springs. These dampers and springs as the important element ' determining the vibration performance of vehicle compact disk Player are used to minimize the vibration which is induced by driving the vehicle. In order to determine the analysis frequency band, we investigated the excitation frequency of road from the vehicle test. As the characteristics of damper and spring were changed, we carried out the vibration test and investigated the change of transmissibility, Also, we carried out the sensitivity analysis for transmissibility and we found out that the properties of damper were the dominant element in the vibration performance of vehicle compact disk player.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.991-996
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• 2011

This study was carried out vibration attenuation of vibration absorber attached to the cantilever beam structure. Modern tank guns are stabilized to allow fire on the move while traversing uneven terrain. However, as the length of the barrel is extended, to meet required muzzle exit velocities, the terrain induced vibrations lead to increased muzzle pointing errors. Thus, reducing these vibrations should lead to increased accuracy. The vibration absorber includes a compliant energy storage device, such as a spring, and a mass secured to the energy storage device. In this study, it accomplished a research in about gun barrel vibration attenuation using tuned mass damper. The barrel was hung from a bungee cord for free-free condition. It accomplished a vibration experiment for verified attenuation efficiency.

• Journal of KSNVE
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• v.10 no.4
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• pp.575-583
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• 2000

In this paper, we design a vibration control system that includes a 3-D.O.F. mass-spring-damper structure for the analytical model of a building that is excited at the base of this structure by an external dynamic force, and one Active Mass Damper(AMD) on the top of this structure to generate control forces fro attenuation of the structural response. Two robust controllers based on $\mu$-synthesis and H$\infty$ optimal control are designed for the structural system to show that the performance of a control system can be degraded by some parameter uncertainties such as mass, stiffness coefficients, and/or damping coefficients. The performance of the two controllers are compared in terms of nominal performance, robust stability and robust performance by simulations.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.508-511
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• 2008

The most landing gear use oleo-pneumatic shock strut to absorb the impact energy during touchdown. The shock strut is composed of the oil damper and the gas spring, especially the oil damper provides resistance force which is proportional to the square of landing speed. In case of high landing speed, the abnormal peak load can be occurred and transferred to the airframe structure. To prevent this, the pressure-relief valve is used to limit the damping force under the specific level. In this paper, it is presented the design process to find optimal damping and analysis results using pressure-relief valve.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.111-117
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• 2007

The nonlinear characteristics of a suspension is directly related to the ride quality of a passenger car. In this study, the nonlinear characteristics of a spring and a damper of a passenger car is analyzed by dynamic experiments using the MTS single-axial testing machine. Also, a mathematical nonlinear dynamic model for the suspension is devised to estimate the ride quality using the K factor. And the effect on the variation of the parameters of the suspension is examined. The results showed that the dynamic viscosity of the oil in a damper was the parameter that most influeced the ride quality of a passenger car for the ride quality of a passenger car.