• Tribology and Lubricants
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• v.10 no.1
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• pp.35-45
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• 1994

The thermohydrodynamic analysis of tilting pad thrust bearing is studied with the consideration of elastic effect of pad. Reynolds equation, deflection equation and energy equation are solved simultaneously with the boundary conditions. Reynolds equation is modified as the approximate form. Pads are supported by the line pivot and the point pivot respectively. Pads are considered as the flat planes. Effects of pad thickness on the performance of thrust bearing are emphasized and the performances of rigid pad and elastic pad are compared. Effects of inlet temperature on performances of the bearing are compared. Dynamic characteristics of both pad supported by line and point pivot are compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.311-318
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• 2016

The lead-rubber bearing (LRB) dissipates seismic energy through plastic deformation of lead core. Under large-displacement cyclic motion, the temperature increases in the lead core. The shear strength of a lead-rubber bearing is reduced due to the heating effect of the lead core. In this study, the seismic responses such as displacement increasing, shear strength and vertical stiffness degradations of LRB due to the heating effect are evaluated for design basis earthquake (DBE) and beyond design basis earthquake (150% DBE, 167% DBE, 200% DBE).

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.324-329
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• 2003

Asynchronus high speed turbo blower of 100HP class with gas bearing supports is developed. The high speed motor is cooled by air and it's RPM is controlled by high frequency inverter to adjust inlet flow rate. Product family is ranged from 50 to 200HP and covered by three frames. Highly efficient impeller is designed and proved by performance test on system. Overall measured system efficiency is 82% including motor and inverter. The motor efficiency is about 95%. It is designed to guarantee to operate at ambient temperature of 35 Deg.C and max 45 DegC. Gas bearing with high load capacity is developed to support heavy rotor on low rotational speed.

• Tribology and Lubricants
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• v.16 no.3
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• pp.208-217
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• 2000

Turbulence in journal bearing operation is examined and the thermal variability is studied for isothermal, convective and adiabatic conditions on the walls within some degree of journal misalignment. An efficient algorithm for the solution of the coupled turbulent Reynolds and energy equations is used to examine the effects of the various factors. The calculation data of turbulent analysis are compared with those of laminar analysis. Heat convection is found to play but a small role in determining friction and load. The friction distribution patterns through the journal bearing are now different with high values at the upstream region of the bearing due to the high speed and low temperature, and a sudden decrease past the pressure maximum.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.616-621
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• 2005

Most machine element, such as gears and bearings, are operated in the mixed lubrication region. Contact between two asperities has an effect on machine life by increasing local pressure. To estimate fatigue lift exactly, asperity contact should be considered as a factor of fatigue liff because this happening produce friction, abrasion and make flash temperature. In this paper, asperity contact is considered as a result of film breakdown when lubricant pressure is not enough to separate two asperities. Contact pressure is calculated to asperity overlap region and added to lubricant pressure. For this model, numerical procedure is introduced and the result on surface roughness and velocity for wheel bearing is presented. Results of EHL analysis for wheel bearing show that asperity contact is occurred at the edge of EHL conjunction where has a insufficient lubricant pressure to separate two surface.

• Progress in Superconductivity
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• v.13 no.1
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.5-14
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• 2012

In the current design codes for anti-freezing layer, the thickness of anti-freezing layer is calculated by freezing depth against the temperature condition. Therefore, they have a tendency of over-design and uniform thickness without the considerations of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential for studying the appropriateness and bearing capacity of road foundation materials as well as their seasonal and mechanical properties to take an appropriate and reasonable design of the road structure system. In this paper, the freezing and bearing capacity characteristics of typical road foundation materials were evaluated in the large scale laboratory test. LFWD (light falling weight deflectometer) was used to determine the change of elastic modulus ($E_{LFWD}$) caused by to the frost heave and thaw. Furthermore, the influence of crushed natural aggregate on the freezing of the subgrade soil was studied to verify the function and effectiveness of the anti-freezing layer.

• Progress in Superconductivity
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• v.11 no.1
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• pp.57-61
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• 2009

A superconductor flywheel energy storage(SFES) system is mainly act an electro-mechanical battery which transfers mechanical energy into electrical form and vice versa. SFES system consists of a pair of non-contacting High Temperature Superconductor (HTS) bearings with a very low frictional loss. But it is essential to design an efficient HTS bearing considering with rotor dynamic properties through correct calculation of stiffness in order to support a huge composite flywheel rotor with high energy storage density. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate HTS bearing magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measured axial / radial stiffness and found bearing stiffness can be easily changed by activated vibration direction between PM and HTS bulk. These results are used to determine the optimal design for a 10 kWh SFES.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1323-1330
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• 2013

A wheel loader is a type of construction machinery that is capable of performing a variety of tasks, and demands on its functional diversity and structural reliability are growing. A wheel bearing is one of the core components that determine the life of the loader; taper roller bearings are commonly used for this purpose. The lifetime of a bearing is typically calculated based only on its load and revolution speed. The initial preload of a taper roller bearing is a critical factor that directly affects its endurance life. In this study, the relations between the endurance life and preload characteristics including the amount of preload according to the weight, rotational speed, and thermal modification applied to tapered roller bearings are presented. When the temperature is $100^{\circ}C$, an excessive preload condition is expected compared with that at room temperature, and the durable life decreases by 20.3 %.

• Steel and Composite Structures
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• v.50 no.4
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• pp.383-401
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• 2024

The research comprehensively studies the axial compression performance of T-shaped concrete-filled thin-walled steel tubular (CTST) long columns after fire exposure. Initially, a series of tests investigate the effects of heating time, load eccentricity, and stiffeners on the column's performance. Furthermore, Finite Element (FE) analysis is employed to establish temperature and mechanical field models for the T-shaped CTST long column with stiffeners after fire exposure, using carefully determined key parameters such as thermal parameters, constitutive relations, and contact models. In addition, a parametric analysis based on the numerical models is conducted to explore the effects of heating time, section diameter, material strength, and steel ratio on the axial compressive bearing capacity, bending bearing capacity under normal temperature, as well as residual bearing capacity after fire exposure. The results reveal that the maximum lateral deformation occurs near the middle of the span, with bending increasing as heating time and eccentricity rise. Despite a decrease in axial compressive load and bending capacity after fire exposure, the columns still exhibit desirable bearing capacity and deformability. Moreover, the obtained FE results align closely with experimental findings, validating the reliability of the developed numerical models. Additionally, this study proposes a simplified design method to calculate these mechanical property parameters, satisfying the ISO-834 standard. The relative errors between the proposed simplified formulas and FE models remain within 10%, indicating their capability to provide a theoretical reference for practical engineering applications.