• Journal of KSNVE
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• v.10 no.2
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• pp.221-228
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• 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 of Machine Tool Engineers Conference
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• 2000.10a
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• pp.216-221
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• 2000

In this study, two mathematical models are first constructed to analyze vibration characteristics of a gear train - spindle system of an NC lathe gear box. One is a lumped parameter model which is used for calculating natural frequencies of the torsional vibration, the other is a finite element model for analyzing lateral vibration and critical speeds of the spindle system. In addition, this study examines some possible resonance conditions such as gear mesh frequencies, 1X shaft rpm frequencies over whole operating speed range, and so on. The results may be helpful to design a machine tool gear box with low noise and vibration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1043-1048
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• 2002

This paper considers the vibration problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we develop an one d.o.f model which describes the radial motion of the center bearing. We find out the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the joint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.929-934
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• 2002

This paper considers the vibration Problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we developed an one d.o.f model which describes the radial motion of the center bearing. We found out that the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the feint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.385-388
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• 2005

Finite element method and Taguchi method were used to reduce the floor impact vibration of the reinforced concrete slab in the apartment buildings. At first, experimental results show that sound peak components to influence the rating of floor impact sound insulation were coincident with natural frequencies of the reinforced concrete slab, and there is a high linear relation between floor impact vibration and sound. The tables of orthogonal arrays were used for finite element analysis with 5 factors related to slab shape parameters and its results were analyzed by statistical method. The most effective factor to reduce the floor impact vibration was the length of living/kitchen room and the floor impact vibration was predicted by 30% reduction in the acceleration peak by the optimal design values of the factors.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.97-104
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• 2015

Compared with a strong axial rigidity due to large intial tension, cable has a weak laterally flexural rigidity. A variety of dynamic loads such as traffic loads and wind loads etc. cause the cables to vibrate significantly and affect the mechanical properties and the performance of cables. Therefore, vibration reduction design is an urgent task to control the vibration of cable-supported bridges. Because a various kind of dampers have shown to reduce the amplitude and duration time of vibration of cable from measured date in field test, damper can be considered that it is effective device significantly to reduce the amplitude and duration time in vibration of cable. Vibration characteristics of cable can change according to manufacturing method and type of established form, and damper has been designed according to distribution of natural frequencies and vibration modes. In this study, numerical analysis is used to show the reduction effects of vibrations and present the design of damper for vibration reduction of cable.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.69-75
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• 2005

Recently it was reported that the vibration problems on the oil pipe support structure of the crude oil carrier were occurred. in order to investigate the vibration characteristics and the causes of the vibration occasionally. the vibration measurements and impact tests for the oil Pipe structure were carried out. From the measurement results severe vibration was caused by the resonance between the transversal natural frequency of the structure and $6^{th}$ order excitation force of the main engine. Providing the proper countermeasures a series of the vibration analyses were carried out based on the measurement results. From the analysis results, it was concluded that the vibration characteristics of the oil pipe structure were affected by the oil pipes, support structure itself, upper deck structure and the installation spaces and the standard design was established for the crude oil carriers.

• Journal of Advanced Marine Engineering and Technology
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• v.4 no.1
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• pp.2-22
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• 1980

In the earlier days, when the diesel engine was used for ship propulsion, its shaft had often been broken by uncertain causes. Bauer suggested, for the first time in 1900, that it resulted from the torsional vibration of the shaft system. From 1901 to 1902, Gumbel and Frahm found out that shaft failures were caused by the resonance of the shaft system in critical speed. Since that time, valuable theories, empirical formulae and methods of vibration analysis were introduced by many investigators such as Geiger, Holzer, Lewis, Carter, Porter, Constant, Timoshenko, Dorey, Den Hartog, Tuplin, Ker Wilson, Bradbury etc. But, as the calculation of the damping energy involves very complicated and uncertain factors, the estimated amplitude of the torsional vibration is incorrect and uncertain. Besides, as high-powered engines have been installed on large vessels or special vessels and exciting force has been increased, new problems of the torsional vibration have continuously occurred. Although we can calculate the approximate natural frequencies or estimate their amplitude and additional stress in the design stage, through the above mentioned studies, the results of the calculations are unsatisfactory, and so much time is needed to carry out the calculation by hand. The authors have developed a computer program to calculate its natural frequencies, the amplitudes and additional stresses of the torsional vibration in the marine diesel engine shafting. In developing the computer program, the authors have paid the special attention to the calculation of the damping energy. To verify the reliability of the developed computer program, the torsional vibration of several propulsion shaftings which are driven by the diesel engine has been analyzed. The results calculted by the authors' computer program show good agreements with those of the actual measurements and are better than the results of engine maker's calculation.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.500-511
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• 2015

In this study, the natural frequencies of the perforated square plate with a square penetration pattern are obtained as a function of ligament efficiency using the commercial finite-element analysis code ANSYS. In addition, they are used to extract the effective modulus of elasticity under an assumption of a constant Poisson's ratio. The effective modulus of elasticity of the fully perforated square plate is applied to the modal analysis of a partially perforated square plate using a homogeneous finite-element analysis model. The natural frequencies and the corresponding mode shapes of the homogeneous model are compared with the results of the detailed finite-element analysis model of the partially perforated square plate to check the validity of the effective modulus of elasticity. In addition, the theoretical method to calculate the natural frequencies of a partially perforated square plate with fixed edges is suggested according to the Rayleigh-Ritz method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.529-534
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• 2002

The receptance method was applied for the analysis of a cylindrical shell with a curvaturated plate attached at the top of the shell. The boundary conditions of the shell considered here were clamped at the bottom and free at the top of the shell. Before the analysis of the shell/plate combined structure, the natural frequencies of the plate and the shell were calculated separately and then they were used in the calculation of the frequencies of the combined structure by the receptance method. The frequency equation of the combined structure was derived from the continuity condition at the junction of the shell and the plate. The frequencies for various curvature factors of the plate were presented and compared with those from ANSYS to show its validity of the present method.