• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.45-51
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• 2009

Conventionally, Al-Sn bearing manufacturing involves casting the Al-Sn alloy and roll-bonding to a steel backing strip. This article will describe the microstructural control of Al-Sn metal bearing alloy following heat treatment. When the pure aluminum rod dipped in the melt of tin maintained below the melting point of aluminum, the melting of aluminum was accelerated with penetration of tin along the grain boundary of aluminum. The length of plate-shaped eutectic tin was decreased with heat treatment time. With even longer heat treatment time over 1 hour the length of eutectic tin didn't decrease any more, while resulting in coarsening of aluminum matrix. Exuded liquid of eutectic tin was formed at the surface of Al-Sn alloy after heat treatment even at below eutectic temperature.

• Journal of Industrial Technology
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• v.35
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• pp.3-8
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• 2015

A study has been made on defects which are formed in manufacturing processes of engine bearing and also on fatigue crack growth behavior in each step of bearing metal manufacturing. After the first step(sinter brass powder on steel plate ; Series A) many voids are made on brass surface and its size is decreased by the second step(rolling process of sintered plate ; Series B). After the third step(re-sintering step of brass powder and rolling ; Series C) the number of voids is decreased and its type shows line. The time of fatigue crack initiation and the growth rate of fatigue crack are in order of Series A, Series B, Series C. These reasons are that void fosters the crack initiation and growth, and residual stress made by rolling process effects on the crack growth rate in Series B, C. In forming and machining processes by use of final bearing metal, crack was observed at internal corner of flange and peeling off was observed at junction between steel and brass. Owing to the above crack and peeling off, it is considered that there is a possibility of fatigue fracture during the application time.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.45-51
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• 2011

A study has been made on defects which are formed in manufacturing processes of engine bearing and also on fatigue crack growth behavior in each step of bearing metal manufacturing. After the first step (sinter brass powder on steel plate ; Series A) many voids are made on brass surface and its size is decreased at the second step (rolling process of sintered plate ; Series B). After the third step (re-sintering step of brass powder and rolling ; Series C) the number of voids is decreased and its type shows line. The time of fatigue crack initiation and the growth rate of fatigue crack are in order of Series A, Series B, Series C. These reasons are that void fosters the crack initiation and growth, and residual stress made by rolling process affects on the crack growth rate in Series B, C. In forming and machining processes by use of final bearing metal, crack was observed at internal corner of flange and peeling off was observed at interface between steel and brass. Owing to the above crack and peeling off, it is considered that there is a possibility of fatigue fracture during the application time.

• Tribology and Lubricants
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• v.34 no.4
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• pp.138-145
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• 2018

Elliptical bearings are widely used for large steam turbines owing to their excellent load carrying capacity and good dynamic stability. Power loss in bearings is an extremely important parameter, especially for high turbine capacities. Optimization of operation conditions and design variables such as bearing clearance and bearing length can reduce the power loss in elliptical bearings. Although changes in the oil supply method have served to increase the efficiency of the tilting pad journal bearing, it has not explicitly improved elliptical bearings. In this study, we verify the static characteristics of an elliptical bearing by changing the direction of oil supply. We evaluate the bearing power loss and bearing metal temperature, and compare the bearing performance and reliability in different test cases. The direction of oil supply is $90^{\circ}$ (9 o'clock) and $270^{\circ}$ (3 o'clock) when the rotor rotates in a counterclockwise direction. We use an elliptical bearing with an inner diameter and active length of 220.30 and 110.00 mm, respectively. Bearing power loss and bearing metal temperatures are measured and evaluated by rotor rotational speed, oil flow rate, and bearing load. The results reveal a 20 reduction in the power loss when the direction of oil supply is 90. Furthermore, the oil film on the upper part of the bearing has a high temperature when the direction of oil supply is $90^{\circ}$. In contrast, when the direction of oil supply is $270^{\circ}$, the oil film on the upper part of the bearing is relatively cold.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.2
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• pp.91-93
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• 2011

This paper is presented for the performance of the Fluid Dynamic Bearing(FDB) by the groove design and the tooling condition. Recently, spindle motors which require smaller size, lower sound noise, lower vibration, and higher speed of the rotation have been placed in high value-added products including Digital Lightening Processors(DLP), Hard Disk Drives(HDD), and ODDs. The spindle motors using the sintered porous metal bearing have higher vibration and acoustic noise by dry contact and large tolerance of the bearing parts. The Fluid Dynamic Bearing (FDB) with grooves is appropriate for spindle motors adequate in regards to mechanical vibration and acoustic noise. The paper shows the performance comparisons of between sintered porous metal bearing and FDB, and each FDBs according to the tooling deviations of grooves by the Finite Element Analysis(FEA) of the mechanical field. This paper shows the methods to make the grooves, the groove's depth, and the prototype of the motor with the fluid dynamic bearing. The performance characteristics of the grooves with the FDB are verified by the experimental results.

• Tribology and Lubricants
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• v.1 no.1
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• pp.88-101
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• 1985

There is a certain relation between the performance characteristics of the porous metal bearing and the porosity. Since the relation is not explicit, author tried to investigate it by numerical analysis and experiment. The analysis and experiment show that the load carrying capacity decreases as porosity increases while attitude angle and friction parameter increase as porosity increases.

• Journal of Welding and Joining
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• v.8 no.4
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• pp.20-26
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• 1990

In this study, to make research on its optimum condition in friction weld when the heating pressure is change during 1.6 to 3.0 $kgf/mm^2$, the experiment was performed with metal bearing under various condition; 1600 r.p.m spindile speed, 0.6 $kgf/mm^2$ preheating pressure, upset pressure 2.6 $kgf/mm^2$, 0.5 seconds preheating time, 1.7 seconds heating time, water and air was ejected 6 $kgf/mm^2$ into the bushing. On the basis of the experimental results, the following conclusion are drawn; 1) At the area of weld interface, the heardness is shown the maximum value and heat-affected zone about 0.5mm both sides. 2) Bending strength is shown the optimum heating pressure 2.4 kgf/mm. 3) With the approach of the flash, Sn is increased only 2 mm in A-alloy structure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.428-431
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• 2005

This paper describes the process design for hot forging of bearing hub. Forging processes of bearing hub are simulated using the rigid-plastic finite element method. In the process called closed die forging without flash, the design of blocker geometry is of critical importance. Forging processes designs are take advantage of computer aided Process planning and experts. But that is difficult to predict metal flow line. So the preform is designed by the expert, and modified through predict metal flow line by CAE. This paper is to approach preform design considered defect such as metal flow and unfitting etc. at the finisher process.

• Tribology and Lubricants
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• v.35 no.2
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.467-468
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• 2008