• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.407-417
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• 2005

An experimental and analytical study was performed to apply the friction pendulum system (FPS) to the main control room of a nuclear power plant. A friction pendulum bearing was fabricated, and the dynamic response of the bearing was evaluated. A partial model of a main control room attached to the FPS was tested on the shake table. The model consisted of a cabinet, a $3m\times3m$ access floor, and four friction pendulum bearings. The artificial time history based on the floor response spectrum of the main control room was used as the earthquake input signal in the test. Comparisons between the analytical study and the experimental study were conducted to verify the results and to extend the experimental study to the range of parameters that could not be experimentally studied.

• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.32-38
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• 1999

An experimental study is performed to investigate the frequency effects of the excitation force on the linear stiffness and damping coefficients of a LOP (load on pad) type five-pad tilting pad journal bearing with the diameter of 300.91 mm and the length of 149.80 mm. The main parameter of interest in the present work is excitation frequency to shake the test bearing. The excitation frequency is controlled independently, using orthogonally mounted hydraulic exciters. The relative movement between the bearing and shaft, and the acceleration of the bearing casing are measured as a function of excitation frequency using the different values of bearing load and shaft speed. Measurements show that the variation of excitation frequency has quite a little effect on both stiffness and damping coefficients. Both direct stiffness and damping coefficients in the direction of bearing load decrease by the increase of shaft speed, but increase with the bearing load.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.173-179
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• 1998

An experimental study is performed to investigate the frequency effects of the excitation force on the linear stiffness and damping coefficients of a LOP (load on pad) type five-pad tilting pad journal bearing with the diameter of 300.91 mm and the length of 149.80 mm. The main parameter of interest in the present work is excitation frequency to shake the test bearing. The excitation frequency is controlled independently, using orthogonally mounted hydraulic exciters. The relative movement between the bearing and shaft, and the acceleration of the bearing casing are measured as a function of excitation frequency using the different values of bearing load and shaft speed. Measurements show that the variation of excitation frequency has quite a little effect on both stiffness and damping coefficients. Both direct stiffness and damping coefficients in the direction of bearing load decrease by the increase of shaft speed, but increase with the bearing load.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.185-190
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• 2016

Damages of the main engine aftmost bearing and the after stern tube bearing tend to increase due to misalignment. And as the shafting system becomes stiffer due to the large engine power, whereas the hull structure becomes more flexible due to optimization by using high tensile thin steel plates. And this is the reason that more sophisticated shaft alignments are required. In this study, the optimum shafting alignment calculation was carried out, considering the thermal expansion effect, exploiting the sensitivity index, which indicates the reasonable position of forward intermediate shaft bearing for shaft alignment. and as the main subject in this study, the elastic deformation on intermediate shaft and main engine bearings occurred by vertical load of shaft mass were examined thoroughly and analyzed allowable load of bearings, reaction influence numbers of all bearings. As the result, a reliable optimum shafting alignment was derived theoretically. To verify these results, they were referred to the engine maker's technical information of main engine installation and being used shafting alignment programs of both Korean Register of Shipping and Det Norske Veritas, their reliability were reviewed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.115-120
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• 2014

Wind power is a type of clean energy source which does not produce carbon dioxide. The wind turbine industry is considered as a major growth industry in many countries. The main cause of wind turbine failure arises in the wind turbine gearbox, and the main type of damage occurs in the bearings and gears. Therefore, predictions of gear and bearing damage are very important to ensure the reliability of the wind turbine reducers used in these systems. In this research, in order to optimize the wind turbine reducer, a series of simulations and redesigns was done using the tool RomaxDesigner. The RomaxDesigner model was used to analyze the bearing life of the duty cycle for a 5 MW wind-turbine pitch drive and to calculate the load in operating states. The reducer was designed to satisfy the life requirement by analyzing bearing damage and calculating the stress values of the main parts of the reducer.

• Tribology and Lubricants
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• v.7 no.1
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• pp.35-39
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• 1991

The performance of the ultra-precision machine tools depends on the steady state characteristics of the main spindle bearings. For excluding the effect of machining error with perpendicularity, conical or spherical bearing has been used. In this paper, steady analysis of the externally pressurized conical gas bearing for ultraprecision is carried out based on the direct numerical method with assumption of point source. As a result of theoretical analysis, design parameters for optimal condition of conical gas bearing are' presented in dimensionless form.

• Tribology and Lubricants
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• v.8 no.1
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• pp.78-83
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• 1992

For excluding the effect of machining error such as perpendicularity, conical and spherical bearing has been used. In this paper, dynamic characteristics of the externally pressurized conical gas bearing for untraprecision main spindle is carried out based on the direct numerical method with assumption of point source. As a result of theoretical analysis, it is verified that coupled stiffness and damping exist and new design parameters for optimal condition of conical gas bearing are presented in dimensionless form.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.336-340
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• 1996

This paper presents the development of a collocated capacitance sensor and its application to the decentralized PID controller design for 4-axis magnetic bearing system. The main feature of the sensor is that it is made of a compact printed circuit board (PCB) so that it can be built in to the actuator coil of the magnetic bearing unit. The signal processing unit has been also developed. Then, decentralized PED controller is designed using simplified rotor system model. Finally, the experimental results on the performance of the collocated sensor based decentralized PID controller for a magnetic bearing rotor system is presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.400.2-400
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• 2002

Recently rotating machines have became high speed and high Power and light weight. Bearings are one of the main components which influence power loss and stability of rotating machines. Appropriate bearing should be selected with considering characteristics of rotating machine. Floating ring journal bearing(FIB) consists of an inner film and outer film, and possess high damping and stability. FJB has been for adopted into turbocharger for the high stability at high operating speed. (omitted)

• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.15-20
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• 2005

This paper describes the PCB drilling using an ultra high-speed air bearing spindle system and micro drill. For this research, we have developed the ultra high-speed air bearing spindle of 125,000 rpm and made an experiment for the application possibility in the PCB drilling. In order to estimate the drilling performance, we have investigated the size and damage of drilled hole, and the wear of drill at 90,000rpm. Results are as follows; we have confirmed the possibility in the PCB drilling of air bearing spindle. In case of micro-drilling PCB at $0.1mm\sim0.3mm$, the increase in the number of drilling has resulted in a bigger size of holes and also a bigger size of damage. It has been found that the wear of micro drill tends to concentrate in the main cutting edge.