• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.9-15
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• 2018

The turbochargers, which are used widely in diesel and gasoline engines, are an effective device to reduce fuel consumption and emissions. On the other hand, turbo-lag is one of the main problems of a turbocharger. Bearing friction losses is a major cause of turbo lag and is particularly intense in the lower speed range of the engine. Current turbochargers are mostly equipped with floating bearings: two journal bearings and one thrust bearing. This study focused on the bearing friction at the lower speed range and the experimental equipment was established with a drive-motor, load-cell, magnetic coupling, and oil control system. Finally, the friction losses of turbochargers were measured considering the influence of the rotating speed from 30,000rpm to 90,000rpm, oil temperature from $50^{\circ}C$ to $100^{\circ}C$, and oil supply pressure of 3bar and 4bar. The friction power losses were increased exponentially to 1.6 when the turbocharger speed was increased. Friction torques decreased with increasing oil temperature and increased with increasing oil pressure. Therefore, the oil temperature and pressure must be maintained at appropriate levels.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.809-822
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• 2013

Base isolation is widely used in seismic resisting buildings due to its low construction cost, high reliability, mature theory and convenient usage. However, it is difficult to design the isolation layer in high-rise buildings using the available bearings because high-rise buildings are characterized with long period, low horizontal stiffness, and complex re-distribution of the internal forces under earthquake loads etc. In this paper, a simple and innovative isolation bearing, named Teflon-based lead rubber isolation bearing, is developed to address the mentioned problems. The Teflon-based lead rubber isolation bearing consists of friction material and lead rubber isolation bearing. Hence, it integrates advantages of friction bearings and lead rubber isolation bearings so that improves the stability of base isolation system. An experimental study was conducted to validate the effectiveness of this new bearing. The effects of vertical loading, displacement amplitude and loading frequency on the force-displacement relationship and energy dissipation capacity of the Teflon-based lead rubber isolation bearing were studied. An analytical model was also proposed to predict the force-displacement relationship of the new bearing. Comparison of analytical and experimental results showed that the analytical model can accurately predict the force-displacement relationship and elastic shear deflection of the Teflon-based lead rubber isolation bearings.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.4
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• pp.61-71
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• 1995

Nowadays the thin-walled metal bearing, which is made seperately from the bearing housing and has the ratio of wall thickness/bearing diameter being less than 1/30, are used in many newly developed large-sized slow speed diesel engines for the purpose of upgarding lubication performance and easy maintenance according to the trends of increasing output per cylinder and lowering engine speed. The type of this bearing has been used generally in many small-sized high speed engines applied for automobile, high speed craft and industrial power generation systems since 1950s. But the tranditional thick-walled bearings, whice are linned white metal on the bearing housing directly, have been installed on the large and slow speed engines until 1990s due to the easy manufacturing procedures. In this study we have calculated optimum dimensions of the metal bearing, fabricated special zigs for crush measurement, model test machine, 2 sets of specimens.(crosshead pin bearing, $\phi$818*552*20mm) for B & W 6S70MC(20, 940*88rpm), and evaluated metal constact phenomena of white metal, its friction coefficient, temparature rise through the model test and field performance test.

• Geomechanics and Engineering
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• v.35 no.1
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• pp.41-54
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• 2023

The use of a skirt, a vertical projection attached to the footing, is a recently developed method to increase the bearing capacity of soils and reduce foundation settlements. Most of the studies were focused on vertical skirted circular footings resting on clay while neglecting the rigidity and inclination of skirts. This study employs finite element limit analysis to investigate the bearing capacity enhancement of flexible and rigid inclined skirts in cohesionless soils. The results indicate that the bearing capacity initially improves with an increase in the skirt inclination but subsequently decreases for both flexible and rigid skirts. However, the rigid skirt exhibits more apparent optimum skirt inclination and bearing capacity enhancement than the flexible one, owing to differences in their failure mechanisms. Furthermore, the bearing capacity of the inclined skirted foundation increases with the skirt length, footing depth, and internal friction angle of the soil. In the case of rigid skirts, the bearing capacity increases linearly with skirt length, while for flexible skirts, it reaches a stable value at a certain skirt length. The efficiency of the flexible footing reduces as the footing depth and soil internal friction angle increase. Conversely, the efficiency of the rigid skirt decreases only with an increase in the depth of the footing. The paper also presents a detailed analysis of various failure patterns, highlighting the behaviour of inclined skirted footings. Additionally, nonlinear regression equations are provided to quantify and predict the bearing capacity enhancement with the inclined skirts.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.160-164
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• 2014

Recently, there has been an active study about friction force of moving parts for automotive. This study is development and evaluation of oil pockets for journal bearing and tappet valve for range extended electric vehicle. Specially, oil pockets are effect on friction force depend on pitch, size, depth. In this study, fine oil pocket was formed using by etched texturing on the journal bearing and tappet valve. And oil pocket analyzed by SEM and friction force test was carried out by tensile tester. Finally, in this study, it was suggested by round and plane part which journal besring and tappet valve.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.497-504
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• 2005

This paper presents the results of experimental studies on the equipment isolation effect considering the floor response. For this purpose, shaking table tests were performed. For the measuring the floor response, numerical analysis was performed. For the isolation for the equipment, Natural Rubber Bearing(NRB), High Damping Rubber Bearing(HDRB) and Friction Pendulum System(FPS) were used. Finally, it is presented that the isolation systems used in this test can be adopted for the small equipment isolation. But the rubber bearing used in this study affected to the temperature change very sensitively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.888-891
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• 2002

This paper presents the lubrication characteristics of a disk type wavy thrust bearing. The hydrodynamic pressure distributions in the fluid film are numerically solved the Reynolds equation and then the bearing load capacity and friction forces acting on the disk are calculated. Especially the effects of number and amplitude of the circumferential waves are investigated for tilted operating conditions. The results showed that the load capacity increases with wave amplitude and optimum wave number exists for given design conditions. Therefore the results can be applied to enhance the lubrication performance of thrust bearing adopted in the scroll compressor.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2163-2166
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• 2004

For designing high Tc superconductor proceeding bearing(HTSJB) which is used on a flywheel energy storage system which requests the free of the bearing loss caused by the friction, it is necessary to understand the basic characteristics of the classical superconductor proceeding bearing because the mechanical characteristics of the HTSJB are identified by the magnetic relationships between the permanent magnet(PM) and the high Tc superconductor(HTS). In this paper, using the method, frozen image model, the force problems between the PM and the HTS were solved and then the dynamic characteristics of the rotor inside of the HTSJB can be expected in advance by using the basic characteristics between the PM and the HTS. The coefficient of friction of the HTSJB was measured in the vacuum environment. From the results, the mechanical characteristics of HTSJB can be identified using the numerical models.

• Tribology and Lubricants
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• v.20 no.3
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• pp.140-144
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• 2004

Water-lubrication ball bearings are required to install in aqueous medium where water is used as coolant or working fluid. However water-lubricated frictional characteristics of stainless steel ball bearing is not will known compared to oil-lubricated frictional characteristics. Furthermore study on friction at high temperature is rare because bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is mostly based on change of failed bearings and parts. Ball bearings and ball screws are used to transmit power in the control rod drive mechanism for an integral reactor and are lubricated with high temperature and high pressure chemically-controlled water. Bearings and power transmitting mechanical elements for a nuclear reactor require high reliability and high performance during estimated lifetime, and their performance should be verified. In this paper, experimental research results of frictional characteristics of water-lubricated ball bearing are reported.

• Tribology and Lubricants
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• v.27 no.6
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• pp.338-343
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• 2011

Laser surface texturing (LST) methods are widely applied now to reduce friction and improve reliability of machine components such as thrust bearings, mechanical face seals and piston rings, etc. In this paper, the effect of dimple shapes on the lubrication characteristics of parallel thrust bearing are studied using a commercial computational fluid dynamics (CFD) code, FLUENT. Pressure and streamline distributions, variations of supporting load, leakage flow rate and friction force, are compared for three different dimple sectional shapes such as circle, pyramid and rectangle type. The lubrication characteristics are highly affected by dimple shapes and number of dimples. The pyramid type dimple shape can support the highest load while the rectangle type is the best in friction reduction.