• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.51-56
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• 1993

The conical bearing can be used to support the radial and thrust load simultaneously. Two circumferential grooves with discrete hole restrictions are made on the bearing surface in order to increase stiffness. In this paper, the dynamic characteristics of this type of bearings are calculated such as stiffness and champing coefficients. As a results of theoretical analysis, it is verified that there exist the groove depth and distance between two grooves which produce the maximum stiffness at the given bearing dimensions.

• Tribology and Lubricants
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• v.10 no.1
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• pp.56-61
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• 1994

The conical bearing can be used to support the radial and thrust load simultaneously. Two circumferential grooves with discrete hole restrictions are made on the bearing surface in order to increase stiffness. In this paper, the dynamic characteristics of this type of bearings are calculated such as stiffness and damping coefficients. As a results of theoretical analysis, it is verified that there exist the groove depth and distance between two grooves which produce the maximum stiffness at the given bearing dimensions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.325-332
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• 2002

This article describes (1) 2 and 3 dimensional electromagnetic finite element models for an active heteropolar radial magnetic bearing, (2) the procedure for obtaining the bearing stiffnesses by simulating the models and (3) the reviews of the models by comparing an experimental test to the ideal closed loop analysis with the stiffnesses calculated from (2). The 3 dimensional model for the magnetic bearing may be very effectively applied to several types of magnetic bearings.

• Tribology and Lubricants
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• v.23 no.6
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• pp.283-287
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• 2007

Permanent-magnet (PM) passive bearings use the repulsive forces between the rotor and the stator magnets for the bearing function. It is desirable that the stiffness of the bearing is maximized with the given volume of the magnet. The stiffness is affected by the magnet strength, the number of layers, and the magnetization patterns. Previously, finite-element method (FEM) has been used to maximize the stiffness of the bearing. In this paper, we used the equivalent current sheet method to calculate the stiffness. The validity of this approach is checked against FEM results. The optimized bearing is applied to a micro flywheel energy storage system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.429-434
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• 2001

This paper has been presented the dynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing two row sources position of air bearing is different from previous investigations in the side of pressure distribution of air film by the wedge effects. An experimental study was performed to compare theoretical analysis. The dynamic stiffness was measured in actual cutting. It helps predicting of air spindle s characteristic in machining of die more precisely. The results of investigated characteristics was applied to air spindle for high speed milling.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.215-220
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• 1994

Results of an experimental investigation on the bearing strength and stiffness of concrete under dowel bars are summarized. The effects of concrete strength bar diameter, and location of the bar on concrete were studied. Based on test results, empirical equations are proposed to predict the, concrete bearing strength and stiffness under reinforcing bars. Cornparisions of analytical arid experimental results are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.80-87
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• 1998

In this study, the effects of residual shaft bow and flexible bearings of a single disk rotor are investigated. The stiffness coefficients of a shaft with initial deflection are different from those of a straight shaft. The stiffness coefficients are calculated using Castigliano theorem considering initial deflections. The stiffness coefficients, which are obtained in this study, are in good agreement with FEM results. The speed which causes zero amplitude is shown to be the square root of the ratio of residual bow amplitude to unbalance eccentricity in the case of rigid bearings and isotropic flexible bearings, but not in anisotropic bearings.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.395-410
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• 2014

Fiber Reinforced Elastomeric Bearings (FREBs) are a relatively new type of laminated bearings that can be used as seismic/vibration isolators or bridge bearings. In an unbonded (U)-FREB, the bearing is placed between the top and bottom supports with no bonding or fastening provided at its contact surfaces. Under shear loads the top and bottom faces of a U-FREB roll off the contact supports and the bearing exhibits rollover deformation. As a result of rollover deformation, the horizontal response characteristics of U-FREBs are significantly different than conventional elastomeric bearings that are employed in bonded application. Current literature lacks an efficient analytical horizontal stiffness solution for this type of bearings. This paper presents two simplified analytical models for horizontal stiffness evaluation of U-FREBs. Both models assume that the resistance to shear loads is only provided by an effective region of the bearing that sustains significant shear strains. The presented models are different in the way they relate this effective region to the horizontal bearing displacements. In comparison with experimental results and finite element analyses, the analytical models that are presented in this paper are found to be sufficiently accurate to be used in the preliminary design of U-FREBs.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.145-150
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• 2000

Out-of-sphericity is degree of deformation of an air bearing sphere deviated from a perfect sphere. This paper investigates numerically the effect of out-of-sphericity error on the radial stiffness of an air bearing Three types of out-of-sphericity modes are considered. in this study the stiffness is calculated from pressure distribution at the bearing surface which is obtained by solving th Reynolds equation. in some cases large out-of-sphericity errors are found to improve the stiffnesses of air bearings. This implies that an air bearing of perfect hemispheres is not necessarily of the best performance. Thus much labor and cost in manufacturing air bearings can be saved, In addition the radial stiffness of an air bearing depends greatly on the application direction.

• Progress in Superconductivity
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• v.12 no.1
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• pp.27-31
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• 2010

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. Many aspects of the quasi-static behavior of flywheel rotors still need to be studied closely, and the rotors require a stable and highly efficient supporting system such as high temperature superconductor (HTS) bearings, which offer dynamic stability without the use of active control. Quasi-static properties of HTS bearings in the radial direction provide data to solve problems which may occur in a running system. Since stiffness in countering rotor vibration is the main parameter for designing an HTS bearing system, we investigated the quasi-static properties of the magnetic force between permanent magnets(PMs) and HTS bulks in the radial direction. We measured radial stiffness, and discovered that bearing stiffness varied greatly depending on the number of active HTS bulks. This is valuable data for predicting the change in stiffness during partial HTS bearing failure. The quasi-static test results are used for optimal design and performance prediction for the 100 kWh class superconductor bearing.