• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.325-330
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• 1999

The dynamic behavior analysis of air-lubricated tilting pad journal bearing which considers start-up, running and shutdown Process were performed. By carrying out the experiment of shaft vibration, measurement of the vibration amplitudes supported by air lubricated tilting pad bearing and analysis of the result, we found more accurate dynamic behavior of the system. There were many investigations in these bearings, but dynamic behavior of startup, shutdown and running process were lacked. By using the experimental data we found the accurate dynamic behavior of the system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.156-161
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• 1999

new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performances of an air-lubricated hydrodynamic journal bearing. This concept features waves on bearing surface. In this study, we present the solution of the compressible Reynolds equation valid for arbitrary Knudsen numbers. Straight wave journal bearing is investigated numerically. The performances of straight wave bearing are compared to the plain journal bearing over relatively wide range of bearing number and eccentricity. The wave journal bearing offers better stability than the plain journal bearing under a13 bearing numbers covered in this study. The bearing load and stability characteristics are dependent on the geometric parameters such as the amplitude and the starting point of the wave relative to the applied load. Under the condition of Knudsen number)0.01, we can not ignore the effect of slip for journal bearing.

• Tribology and Lubricants
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• v.12 no.1
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• pp.29-35
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• 1996

The static and dynamic stability analysis of air-lubriceted tilting pad journal bearing which considers tilting effect of each pad and preload but neglects pad inertia were performed. And these characteristic analysis were performed with elasticity effect too. A direct numerical method is used in calculating the static characteristics such as load carrying capacity, firction force and perturbation method is used for calculation of dynamic characteristics. The stability analysis was performed with the variation of bearing number, eccentricity ratio and attitude angle considering pad elasticity effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.608-613
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• 2003

In this paper, the effect of interconnected boundary between journal and thrust bearings on the performance of self-acting air-lubricated bearings is investigated. When journal and thrust bearings have common boundary, conventional boundary condition which assumes that the boundary pressure is equal to atmosphere is no more valid. Instead, new boundary condition by mass conservation at interconnected boundary is needed. To do this, a duct model satisfying mass conservation at interconnected boundary is developed. Using this model, pressure distribution at interconnected boundary is numerically analyzed with changing the volume of interconnecting part. As a result, it is shown that load capacity of thrust bearing can be greatly increased when journal and thrust have a common boundary.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.212-219
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• 2001

This paper describes a durability characteristics of an air-lubricated bump foil journal bearing for high speed turbomachinerys at room temperature. At first, lift-off test and load capacity test were performed to understand the general characteristics of an air-lubricated bump foil journal bearing. A 52N weighted bump foil bearing sleeve was lifted off from a rotating journal at about 3,000rpm, and produced a load capacity of 500N at an operating speed of 15,000rpm. The next was 500 cycles lift-off test with an air-lubricated bump foil journal bearing that had a molybdenum disulfide(MoS$_2$) solid lubricant coated top foil. Data from measuring bearing torque and temperature and the observation of rubbing surface were included in results. Therefore the results of this work will aid in proving durability of air-lubricated bump foil journal bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.353-362
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• 2000

Herringbone groove journal bearing (HGJB) is developed to improve the static and dynamic performances of hydrodynamic journal bearing. In this study, static and dynamic compressible isothermal lubrication problems are analyzed by the finite element method together with the Newton-Raphson iterative procedure. This analysis is introduced for prediction of the static and dynamic characteristics of air lubricated HGJB for various bearing configurations. The bearing load characteristics and dynamic characteristics are dependent on geometric parameters such as asymmetric ratio, groove depth ratio, groove width ratio and groove angle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.197-203
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• 2001

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.13-17
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• 1992

최근 정보, 통신 광산업 등 첨단산업의 발달과 함께 부품의 초정밀가공및 특정에 대한 필요성이 높아지고 있다. 이에 따라 초정밀 가공기 및 초정밀계측기기등의 개발이 활발히 이루어지고 있으며, 이들에는 공기베어링두축이 널리 사용되고있다. 이 같이 초정밀 기기의 주축으로 공기베어링이 주로 이용되는 이유는 다른 베어링에 비해 윤활특성상 운동정도가 높고, 저 마찰특성 등의 장점을 가지고있기 때문이다. 본 연구에선 실험적으로 초정밀가공기용 공기베어링주축의 회전정도에 영향을 미치는 인자들의 상관관계를 파악하여 주축설계 및 제작시의 성능향상방법과 이론적 해석의 기초자료를 제시하고자 한다. 또한 공기베어링주축의 구조에 따른 정적 강성 및 회전정도를 비교하여 구조특성에 따른 차이점을 살펴보고, 주축의 강성과 불평형질량(unbalance mass)에 따른 회전 정도의 변화를 측정하였다.

• Tribology and Lubricants
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• v.17 no.2
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• pp.116-123
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• 2001

A theoretical analysis has been undertaken to show the influence of bearing geometry on the steady state characteristics of air lubricated spherical tilting pad bearings. The geometry variations considered are the number of pads, the eccentricity ratio, the direction of load, and the preloading. Dynamic characteristic equations are derived with pad assembly method.

• Tribology and Lubricants
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• v.17 no.2
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• pp.97-108
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• 2001

This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.