• Tribology and Lubricants
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• v.19 no.1
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• pp.15-20
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• 2003

The purpose of the paper is to investigate the effects of design parameters on the noise of a rotor- bearing system supported in oil lubricated journal bearings. Effects of radial clearance and width of the bearing, lubricant viscosity and mass eccentricity of the rotor are also examined. Numerical results of the parametric studies are summarized through graph for the A-weighted sound pressure level of the bearing with respect to the rotational speed of the rotor. Results show that the sound pressure level of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing. The high viscosity of the lubricant slightly decreases the noise of the bearing, but its effect is relatively very low at high speed. The results of the paper could be an aid in the low noise design of rotor-bearing system supported in oil lubricated journal bearings.

• Tribology and Lubricants
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• v.29 no.5
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• pp.318-323
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• 2013

Overheating in electrical motors results in detrimental effects such as degradation of the insulation materials, demagnetization of magnets, increases in Joule losses, and decreases in motor efficiency and lifetime. Thus, it is important to find ways to dissipate heat from the motor and to keep the motor operating at its most efficient temperature. In this study, a new design to guide air flow through a given brushless direct current (BLDC) motor is developed and the design is analyzed, specifically by using computational fluid dynamics (CFD) simulations. The results showed that the temperature distribution in the three proposed models is lower than that in the original model, although the speed of the cooling fan in the original model reaches a very high value of $15{\times}10^3$ rpm. The results also showed that CFD can be effectively used to simulate the heat transfer of BLDC motors.

• Tribology and Lubricants
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• v.12 no.3
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• pp.100-106
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• 1996

Gerotor pumps and motors are widely used in lubrication and hydraulic actuator systems. Compared with internal gear pumps and motors, they have many advantages. However, the gerotor profiles have not been suff'lciently analyzed theoretically. Therefore, it is very difficult for designer to decide the specifications of the gemtor profiles, and calculation of flow rate and minimum distance of clearance in the contact point of inner and outer rotor is not yet confirmed. In this paper, when we design inner and outer rotor concurently, we have analyzed the gerotor profiles and displayed the calculated results such as flow rate, minimum distance between inner and outer rotor and gerotor profiles.

• Tribology and Lubricants
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• v.15 no.1
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• pp.17-23
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• 1999

A Gerotor hydraulic motor is a planar mechanism consisting of a pair of rotors one of which encloses another rotor. The motion of the inner-rotor relative to the outer-rotor is produced by the pressure difference between the adjacent chambers. A design method of inner-rotor tooth profile using unit tangential vectors is presented in this work. Based on the relationships derived, the influence of the eccentricity of inner-rotor and the radius of circular arc tooth on the flow rate, torque and curvatures were investigated. It was shown that the flow rate and mean torque is proportional to eccentricity, but inversely proportional to the radius of circular arc teeth. Also, the maximum value of the equivalent curvature is increased as the eccentricity and the radius of circular arc teeth increased.

• Tribology and Lubricants
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• v.26 no.2
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• pp.129-135
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• 2010

Geckos have a unique ability to cling to ceilings and walls utilizing dry adhesion. Their foot pads are covered by a large number of small hairs (setae) that contain many branches per seta with a lower level of spatulae. Their fibrillar structure is the primary source of high adhesion. In this study, we construct the adhesion design database for biomimetic adhesive system. A simple idealized fibrillar structure consisting of single array of beams is modeled. The fibers are assumed as oriented cylindrical cantilever beams with spherical tip. We consider three necessary conditions; buckling, fracture and sticking of fiber structure, which constrain the allowed geometry. The adhesion analysis is performed for the attachment system in contact with rough surfaces with different s values for different main design variables-fiber radius, aspect ratio and material elastic modulus and so on. The developed adhesion design databases are useful for understanding biological systems and for guiding of fabrication of the biomimetic attachment system.

• Tribology and Lubricants
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• v.15 no.2
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• pp.193-198
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• 1999

Applying design methodology, new type friction tester has been developed. Functional analysis has been executed and functional structure were constructed during the conceptual design. Optimal solution has been selected and a proto model has been manufactured according to the conceptual design. Using the tester developed in the laboratory, frictional characteristics of natural rubbers have been experimentally analyzed. Friction coefficient has been calculated from the measured normal force and friction force under various speeds, loads, and temperatures. The corelations between the various operating conditions and friction coefficients have been verified. Especially, drag friction due to the visco-elastic behavior of the rubber has been observed in this analysis.

• Tribology and Lubricants
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• v.22 no.2
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• pp.87-92
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• 2006

In tread brake of freight cars, brake force is produced by the friction between the wheel and the brake shoe. Friction coefficients associated with the brake power, weight variation and brake shoe types should be sensitively treated as the design parameters. The conditions of the car, empty and loaded, should also be taken into consideration in brake force design and the control of brake force has some limitations in terms of the brake system design so that the brake friction materials selection should be considered as important measures to solve that difficulties. Friction characteristics of brake friction materials should remain within the range of maximum and minimum value and the friction performance should remain stable regardless of brake time and temperature. This study presented an experimental evaluation method to secure optimum brake performance by keeping safe brake effect and brake distance by the friction coefficient of the brake shoe of the freight cars.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.253-257
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• 2000

This paper reports on the development of the analysis program of the piston skirt system, PS-LAP. It is essential to verify the stability of the design and to improve the performance of the system. In order to do that efficiently, it is required that integrated and interactive simulation analysis program. PS-LAP is developed in the base of the object-oriented, capsulation, modulization, OLE(objected linking and embedding) and variational design theory. So it contain the expandability and flexibility of the structure. In addition to that, it is programed to make the convenient user interface by using the visualization programming. It can support the modification of the piston skirt shape, lubrication condition and so on. It is expected to reduce the money and effort for design the piston skirt system.

• Tribology and Lubricants
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• v.24 no.5
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• pp.228-233
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• 2008

In this study, the methodology for determination of shoulder height in the internal shape design of ball bearing using 3D contact analysis is proposed. The static analysis of a ball bearing was performed to calculate the distribution of applied contact load and angles among the rolling elements. From each rolling element loads and the contact geometry between ball and inner/outer raceway, 3D contact analyses using influence function are conducted. These methodology is applied to HDD ball bearing. A critical axial load and a critical shoulder height which are not affected by edge are calculated. The proposed methodology may be applied to other rolling element bearing for the purpose of reducing the material cost and improving the efficiency of the bearing design process.

• Tribology and Lubricants
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• v.36 no.2
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• pp.96-104
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• 2020

The electric vehicle industry is rapidly developing because of enforced environmental regulations, and several studies have been conducted on the multispeed transmission to improve the fuel efficiency of electric vehicles. Among these studies, research on the power density improvement of electric vehicle transmission is critical. Thus, the optimal design of the gear train is necessary to enhance transmission efficiency. In this study, an optimal design methodology for the lightweight two-speed transmission of electric vehicles is proposed. Because a multispeed transmission has many operating conditions and equality and inequality constraints, a new gear design method that combines analytical and iterative methods is applied without using complex optimization algorithms. Sets of possible design variables are generated considering the operating conditions and various design variables. The modules and face width ratios of each stage gear that satisfy the corresponding operating conditions are analytically calculated. The volume of the gear train is calculated, evaluated, and arranged using these values to determine the optimal solution for minimizing the volume, and the proposed methodology is applied to the actual model to verify its effectiveness. The design of a two-speed transmission with multiple operating conditions and constraints without complicated optimization algorithms can be optimized.