• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_1
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• pp.659-667
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• 2021

This paper develops the theory for a novel fault-tolerant, permanent magnet biased, 4-active-pole, double plane, homopolar magnetic bearing. The Lagrange Multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrices for the failed bearing. If any of the 4 coils fail, the remaining three coil currents change via a novel distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. Magnetic flux coupling in the magnetic bearing core and the optimal current distribution helps to produce the same c-core fluxes as those of unfailed bearing even if one coil suddenly fails. Thus the magnetic forces and the load capacity of the bearing remain invariant throughout the failure event. It is shown that the control fluxes to each active pole planes are successfully isolated. A numerical example is provided to illustrate the new theory.

• Tribology and Lubricants
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• v.20 no.3
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• pp.119-124
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• 2004

Engine bearing system is generally affected by aeration. In this paper, the aeration effects on the engine crankshaft bearing system were studied. To do this, unsteady oil flow analysis on the engine crankshaft oil circuit system was carried out. And aeration effects on the bearing system were simulated to figure out lubrication characteristics of the each bearing such as oil flow rate, minimum oil film thickness, friction loss and increase of oil temperature.

• Tribology and Lubricants
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• v.16 no.1
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• pp.39-45
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• 2000

In this paper, the effects of shaft and bearing flexibilities are investigated for the accurate modeling of a shaft-bearing system supported by ball bearings. Generally, rolling bearings are modeled by simple rigid pin-joint in the mechanical design. However, they can no longer be modeled by ideal boundary conditions in the advanced applications because the rigid pin-joint model cannot satisfy the current trends of mechanical design decreasing mass and reducing volume. Consequently the flexible support model of ball bearing is investigated using the static analysis module developed by A .B. Jones and T. A. Harris. A simple two-bearing system, supported by two deep groove ball bearings and radially loaded on the shaft midway between the bearings, is utilized to validate the coupled model of shaft-bearing system. Numerical computations using the model indicate that the shaft span length, locating/floating bearing arrangements and applied bearing size are significant factors in determining the mechanical behaviors. The flexible support model of ball bearing can be escaped to over-estimate in the bearing fatigue life. The proposed simple design formulation obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft span length/shaft diameter (L/d).

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.145-151
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• 2006

Wheel bearing unit has been exclusively applied to car wheel supporting device. The seal for wheel bearing is required to have both high sealing effects and low reaction forces because wheel bearing are operated on adverse environmental conditions such as mud and splash water. High sealing effects are for the protection of bearing ball wear from dust influx. In order to ensure high sealing effects, it is a easiest way to increase contact force which are affected by geometric characteristics, material properties and interferences between seal and inner bearing but induces higher wear phenomena. Interferences in all variables are most important factor to determine the performance of wheel bearing. In this study, optimization of interference amount was performed with finite element analysis with commercial code ABAQUS. For the sake of finite element analysis, tensile tests of rubber material were conducted and governing equation of nonlinear behavior was achieved. Hock-up bearing was manufactured with optimized interference amount. Results of torque and mud spray tests using this bearing unit are performed. Less torque and moisture influx of bearing with optimized interference amount is evidence to validity of this study.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.96-100
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• 2011

The hydrostatic bearings have a relatively small run-out comparing to its shape error by fluid film effect in hydrostatic state as like pneumatic bearing and have a high stiffness, load capacity and damping characteristics. As there is no maintenance and semipermanent in these bearing type, it has been usually adopted as main spindle bearing for grinding machine. In this thesis, to develop hydrostatic bearing for high speed spindle, the cooler setting temperature, bearing clearance and nozzle pressure of belt-driven hydrostatic bearing are investigated. The bearing temperature is decreased, as the cooler setting temperature is lower, nozzle pressure is higher and bearing clearance is wider. The front temperature of bearing is nearly $8^{\circ}C$ higher than the rear one up to 13,000 rpm of spindle revolution. The thermal deflection of X-axis is ${\pm}16\;{\mu}m$ in range of 12,000 rpm-13,000 rpm. Therefore, it is conformed that the built-in motor hydrostatic bearing can be used to high speed spindle.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.590-597
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• 2011

The IDRS provides detection, classification and bearing/range estimation by performing wavefront curvature analysis on an intercepted active transmission from target. Especially, a estimate of the target bearing/range that significantly affects the optimal operation of own submarine is required. Target bearing/range can be estimated by wavefront curvature ranging which use the difference of time arrival at sensors. But estimation ambiguity occur in bearing/range estimation due to a number of peaks caused by high center frequency and limited bandwidth of the intercepted active transmission and distortion caused by noise. As a result the bearing/range estimation performance is degraded. To estimate target bearing/range correctly, bearing/range estimation method that eliminate estimation ambiguity is required. In this paper, therefore, for wavefront curvature ranging, NLS cost function with curve fitting method is proposed, which provide robust bearing/range estimation performance by eliminating estimation ambiguity. Through simulation the performance of the proposed bearing/range estimation methods are verified.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.1
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• pp.1-6
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• 2002

In order to study the characteristics of fiber reinforced bearing, the steel plates of laminated rubber bearing were replaced with fibers which have same effects of steel plates. The comparison of vertical test and horizontal test of laminated rubber bearing and fiber reinforced bearing shows that the effective damping of fiber reinforced bearing is higher than laminated rubber bearing. This result implies the high energy dissipation ability of fiber reinforced bearing under earthquake excitation. These fiber reinforced bearing can be applied to the low-coast building.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.1974-1980
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• 2001

The control algorithm of a new type self-bearing step motor is presented. The motor actuator is used for both motor and bearing functionality without any redundant coil windings or redundant electromagnets. The self$.$bearing step motor layout and its control method are described. A linearized farce-current-displacement relationship is derived. As the result of the unbalance response approach, the constant torque production is possible fur the supply current regulation algorithm. And even if the bearing functionality is added in the motor functionality, no additional current for bearing functionality is possible, and this leads to minimize the net power loss. Also, the unbalance response shows the independent bearing force and motor torque.

• Tribology and Lubricants
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• v.13 no.1
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• pp.70-75
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• 1997

The lubrication characteristics of high-speed ball bearings at oil-starvation have been investigated empirically using the bearings employed in small industrial gas turbine engines. For the close structural simulation, experiments carried our with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be applied to the design and the development of gas turbine engines. Testing was done by simulating the oil-starvation conditions in engines, such as stopping the oil-supply to the bearing during normal operating, starting without oil-supply at atmospheric temperature, and accelerating with oil-supply at atmospheric temperature. From this study, the relative comparison of the frictional resistance and the resistance due to the bearing cavity oil was demonstrated visually, and the resistance due to the bearing cavity oil was dominant in the resistance of bearing at high speed.

• Tribology and Lubricants
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• v.14 no.1
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• pp.14-22
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• 1998

This paper describes the effects of exciting frequency on the stiffness and damping coefticients of a 5-pad tilting pad journal bearing, LOP (load on pad) type. The stiffness and damping coefficients are investigated experimentally under the different values of exciting frequency, bearing load and shaft speed. These coefficients are estimated by measuring the response of the relative displacement between the bearing and the shaft and acceleration of the bearing due to the known exciting loads acting on the bearing. In order to analysis the response of exciting load, displacement and acceleration, a FFT analyzer is used. It is shown that the variation of exciting frequency has a little effect on both the stiffness and damping coefficients. Both the stiffness and damping coefficients in the loading direction are decreased by the increase of shaft speed but increased by the increase of bearing load.