• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.100-109
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• 2004

Is this study, results of static pile load tests of in-situ cast piles in weak or uncemented sedimentary rock layers have been analyzed and presented. Consdierations on the characteristics of soils sedimentary rocks have been made. From the measurements of strain gauges and extensometers the relationship of unit skim friction versus displacement and that of unit end bearing versus displacement have been obatined to verity the characteristics of bearing capacity of this uncemented sedimentary rock layers. Also, a comparison has been made between ultimate skin friction in compression and tension.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.340-345
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• 2001

In this paper, We have studied on the critical vibration limits of spindle unit for the high speed ball pen tip processing machine. The vibration of bearing can be measured by FFT, and the influence of vibration amplitude due to the Unbalance, bearing deflect, bite and timing belts tension are analyzed. So, the critical vibration limits of spindle is determined by the X, Z directional vibration of spindle Unit.

• Journal of the Korean Geotechnical Society
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• v.26 no.5
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• pp.5-13
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• 2010

For the development of design chart for drilled shafts socketed into weathered zone, the 6 bi-directional pile load tests with load transfer measurements done in two in-situ sites were performed. Also, DCPTs were performed in each test point. Maximum unit skin frictions and maximum unit end bearing capacities from pile load test results were analyzed. Inter-relationships between DCPT's characteristics were also analyzed. In the soils, the inter-relationships of maximum unit skin friction and DCPT appeared so low. But in the weathered zones, inter-relationships between maximum unit skin friction / maximum unit end bearing capacity and DCPT were so high that the coefficient of correlation is over 0.70.

• Tribology and Lubricants
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• v.10 no.2
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• pp.43-50
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• 1994

The hydrodynamic bearing is accepted in many rotating systems because it has a large load carrying capacity. But the anisotropic pressure distribution of the bearing can arise the unstable vibration phenomenon over a certain speed. The magnetic bearing is an active element so that the unstable phenomenon of the hydrodynamic bearing, which is induced by the anisotropic support pressure of the oil film, can be controlled if the control algorithm and the controller gains are chosen appropriately. In this study, we investigate the stabilization method of the hydrodynamic bearing system composing the hybrid bearing which is the single unit of hydrodynamic bearing and magnetic bearing. The load carrying conditions of the hybrid bearing is modelled by the sum of the stiffness and damping coefficients of the hydrodynamic and the magnetic bearings in each direction. The dynamics of the rotor is analyzed by the Finite Element Method and the stability limit is determined by the eigenvalues of the hybrid bearings and shaft system. The eigenvalue study of the system shows that the stability limit of the hybrid bearing is increased compared to that of the hydrodynamic bearing. A Small increment of the stiffness and damping coefficient of the hybrid bearings by the magnetic actuators can increase the stability limit of the system. In this paper we tried to show the design references of the hybrid bearings by using the nondimensional bearing parameters. The analysis results show the possibilities of the stability limit increment of the hydrodynamic bearing system by combining the magnetic bearing.

• The KSFM Journal of Fluid Machinery
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• v.12 no.6
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• pp.33-40
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• 2009

The temperature of vertical pump bearing metal in the pumped storage power plant has been high enough to shutdown the unit. Attempts such as decreasing the oil supply temperature, increasing the bearing oil gap etc. were performed to resolve the problem, but the issue was not resolved. Finally, the high bearing metal temperature was corrected by adjusting the bearing preload. The preload is formed by the oil wedge between the journal surface and bearing pad surface and the degree of preload is determined by the machined radial clearance, assembled radial clearance, rotor journal diameter etc. This paper focuses on the analysis of the preload depending on the bearing parameters and the result of the modification of the bearing following the analysis. The bearing metal temperature dropped as much as $20^{\circ}C$ which was similar as expected by software calculation. But the shaft vibration could increase when the assembled radial clearance is excessive. So, the adjustment of the bearing preload for the tilting pad type journal bearing should be carefully performed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.801-806
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• 2015

Journal bearings support rotors using fluid film between the rotor and the stator. Generally, journal bearings are used in large rotor systems such as turbines in a power plant, because even in high-speed and load conditions, journal bearing systems run in a stable condition. To enhance the reliability of journal-bearing systems, in this paper, we study health-diagnosis algorithms that are based on the supervised learning method. Specifically, this paper focused on defining the unit of features, while other previous papers have focused on defining various features of vibration signals. We evaluate the features of various lengths or units on the separable ability basis. From our results, we find that one cycle datum in the time-domain and 60 cycle datum in the frequency domain are the optimal datum units for real-time journal-bearing diagnosis systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.162-167
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• 2002

An automotive wheel bearing is one of the most important components to guarantee the service life of a passenger car. The endurance life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, temperature, loading conditions, bearing geometry, internal clearance and so on. In this paper, we analyze the relation between loads and deformations of wheel bearing units. On the basis of it, we calculate the endurance life of wheel bearing units and suggest a method to determine the initial contact angle to achieve a maximum endurance life with considering stress concentration.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.140-147
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• 1996

Machining accuracy of machine tools spindles using the hydrostatic bearing, largely depends on the static stiffness and the thermal deformation of the spindle unit. In this paper, the modelling and static, thermal analysis of the hydrostatic spindles were performed for the relationship between the design variables like the bearing span, overhang, bearing stiffness and static stiffness at spindle. The goal of optimization is the mazimum, static stiffness at spindle nose with lower temperature rise in hydrostatic bearing. Temperature rise of hydrostatic bearing is minimized with the variables of spindle diameter and oil supply pressure. Finally, validity of the proposed algorithm is verified by improving the static, thermal performance of the existing hydrostatic spindles.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.95-100
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• 2002

Built-in Eccentric Bearing-Torsional Spring (BEBTS) type Automatic Belt Tension Unit (ABTU) is one of typical belt tension units. The BEBTS type ABTU system frequently experiences torsional vibration about its pivot due to the variation of belt tension. However, it is very difficult to analyze the rotational (or torsional) vibration of the ABTU because the exciting moment varies according to the change of belt tension. To get over this difficulty, in this paper. the ABTU was simplified as 1-DOF translational motion model in the tangential direction. Its equation of motion was derived and solved. The time history and frequency responses were computed and examined for three of BEBTS type ABTUs which are made by different manufacturers but the tame kind.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.441-451
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• 2006

It is known that ball bearings mounted in housing or on shaft are playing a key role to keep it running smoothly. The roundness of a housing bore on which bearing outer ring is mounted with interference has directly affected the running accuracy of bearing. The running accuracy of bearing, therefore, can extend the significant influence to the rotating machinery as well. In this paper, bearing's vibration and fatigue life considering raceway roundness of ball bearing before and after mounted in housing bore are theoretically estimated. To perform analysis, a simple three degrees of freedom model was proposed and then Newton-Raphson iterative method was introduced to be utilized in the analysis. The results show that the vibration magnitude of ball bearing fitted into housing unit is appeared considerably larger than the one of its pre-assembling. And theoretical $L_{10}$ life which ninety percent of the bearing population will endure decreased in about fifty percent.