• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.6_spc
• /
• pp.721-728
• /
• 2016

The combined rotational and translational dynamic vibration absorbers (DVA) with no dampers for the beam vibration control can effectively isolate the vibration within the external excitation force region. This paper investigates the damping efficacy for the combined rotational and translational dynamic vibration absorbers to impose some robustness to the DVA system for the excitation force frequency variation. The beam is assumed to be subjected to a concentrated harmonic excitation force. The solution to the problem is found based on Galerkin method.

• Journal of KSNVE
• /
• v.10 no.2
• /
• pp.221-228
• /
• 2000

In this paper, analytical study is performed to reduce residual vibration in seeking mode of optical pick-up. The conditions for acceleration adn deceleration time in trapezoidal velocity profile to reduce residual vibration are derived for undamped vibration system. To verify the validity of conditiosn two example studies are carried out. Numerical and experimental implementations for flexible arm system attached to moving part show that residual vibration is effectively reduced by calculated velocity profile. In addition, simulation study for optical pick-up reveals that by changing natural frequency to resonance frequency the conditions derived assuming undamped system can be applied to obtain velocity profile for minimum residual energy in damped vibration system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.147-156
• /
• 2007

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigate the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a energy loss ratio of cable potential, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, it is assumed to exist three kinds of multi-mode patterns such as ambient vibration, support excitation and rain-win induced vibration. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5. In case of support excitation or rain-wind induced vibration is between 0.5 and 1.0. In this study, the effects of cable sag and inclination angle are included in the asymptotic design equation of damped cable structures.

• Journal of the Semiconductor & Display Technology
• /
• v.5 no.4 s.17
• /
• pp.41-45
• /
• 2006

Micro vibration isolation, typically originated from ground, is always a prime concern for the nano-measurement instruments such as Atomic Force Microscopes. A four mount active vibration isolation system is proposed in this paper. Modeling and control of such a four mount system was analyzed. Combined active-passive isolation principle is used for vibration isolation by mounting the instrument on a passively damped isolation system made of Elastomer along with the active stage in parallel that consists of very soft actuation system, the Voice Coil Motor. The active stage works in combination with the passive stage for working as a very low frequency vibration attenuator.

• Journal of Advanced Marine Engineering and Technology
• /
• v.14 no.2
• /
• pp.35-47
• /
• 1990

The natural frequency of lateral vibration for ship's propulsion shafting tends to become lower as the relative stiffness of supproted system of the propulsion shafting decreases and the weight of shafting increases. Especially, the propulsion shafting of high-power ships such as car ferries, roll-on/roll-off, and container ships are susceptible to lateral vibration for their resonant speeds are happened to be in ordinary operating speed ranges. So far, many papers on the lateral vibration of ship's propulsion shaftings are published but they treated mainly special cases and not explained explicitly the calculation process. In this paper, the calculation processes of undamped and also forced damped lateral vibration by the transfer matrix method are presented and the calculation programs are developed. With the developed computer programs, a ship's propulsion shafting which was introduced on the published paper is analyzed for its lateral vibration and also the lateral vibration of the main drive shaft for a lathe is calculated to show the availiability of developed computer programs.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.289-293
• /
• 1996

Vibration absorber is used to protect the primary system from steady-state harmonic disturbance. By attaching the absorber to the primary system which is modeled as a SDOF system, the new system becomes two DOF system. Depending on the driving frequency on the original system, the absorber needs to be carefully tuned, that is, to choose adequate value of the absorber mass and stiffness, so that the motion of the original mass is a minimum. This paper presents the effects of resonance frequency ratio and of vibration absorber with oil damper and coil spring for linear damped primary systems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1609-1614
• /
• 2000

This paper presents the modeling, theoretical formulation, and stability analysis for a combined system of a spinning disk and a head that contacts the disk. In the analytical model, head interface is considered by a rotating mass-spring-damper system together with a frictional follower force on the damped annular disks. The method of multiple scales is utilized to perform the stability analysis that shows the existence of instability associated with parametric resonances. This instability can be effectively stabilized by increasing the damping ratio of a disk.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.808-812
• /
• 2002

The feasibility of using elastic dampers to mitigate earthquake-induced structural response is studied in this paper. The properties of elastic dampers are briefly described. A procedure for evaulating the elastic damping effect when added to a structure is proposed in which the damping effect of elastic dampers is incorporated into modal damping ratios through an energy approach. Computer simulation of the damped response of a multi-storey steel frame structure shows significant reduction in floor displacement levels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.224-230
• /
• 1996

In the mechanical systems with large damping, the conventional SDM method developed for no damping systems will lead to an error solution. Here, we introduce a SDM method based on the experimental modal model for large damping systems. The sensitivities of natural frequencies and mode shapes with respect to mass, damping, and stiffness coefficients of structures are used to calculate the position and quantity of modification, and predict the new dynamic characteristics. Through numerical simulation and experiment, the effectiveness of the proposed method is tested.

• The Science & Technology
• /
• v.8 no.12 s.79
• /
• pp.61-64
• /
• 1975

An expression for the vibrational frequency of diatomic molecular is obtained by using molecular gas temperature T and molecular gas mean-free path λ. And when λ/T →2.59, beca use of the damped vibration, a diatomic molecular gas is Impeded about transportation. If transfortation is not attained with this condition, rectilinear motion of a diatomic molecular gas can't maintain for the equilibrium state.