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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Tribologists and Lubrication Engineers
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Journal DOI :
The Korean Society of Tribologists and Lubrication Engineers
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Volume & Issues
Volume 29, Issue 6 - Dec 2013
Volume 29, Issue 5 - Oct 2013
Volume 29, Issue 4 - Aug 2013
Volume 29, Issue 3 - Jun 2013
Volume 29, Issue 2 - Apr 2013
Volume 29, Issue 1 - Feb 2013
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Elastohydrodynamic Lubrication Analysis of a Lundberg Profile-type Cylindrical Roller
Park, Tae-Jo ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 353~359
DOI : 10.9725/kstle.2013.29.6.353
The rollers and/or races in cylindrical and tapered roller bearings should be profiled to relieve high edge stress concentrations caused by their finite lengths and misalignment. In this study, a numerical analysis was performed to investigate the elastohydrodynamic lubrication (EHL) of a Lundberg profile-type cylindrical roller. A finite difference method with fully nonuniform grids and the Newton-Raphson method were used to present detailed EHL pressure distributions and film shapes, as well as the variations in the minimum and central film thicknesses with the profile modification coefficient. In the Lundberg profile, the maximum pressure and minimum film thickness always occurred near the edges. Proper modification of the Lundberg profile considerably increased the minimum film thickness.
Effects of Hardness on Sliding Wear Behavior of Tempered Bearing Steel
Lee, Han-Young ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 360~365
DOI : 10.9725/kstle.2013.29.6.360
In this study, sliding wear tests were conducted to investigate the effects of tempered hardness on the sliding wear behavior of bearing steel. At a sliding speed of 0.3 m/s, the wear resistance of bearing steel with a tempered hardness of HRC 54 was superior to that with HRC 62. It was found that bearing steel with HRC 54 showed a strong tendency for the occurrence of oxidation wear at that speed, compared to that with HRC 62. This would be due to the troostitic structure of bearing steel with HRC 54, which is highly susceptible to corrosion. In this context, it is considered that sliding wear behavior could be affected by the corrosion resistance of the material.
A Study on Wear Mechanism in Diamond-like Carbon Coated Surface by Finite Element Analysis
Lee, Jun-Hyuk ; Park, Tae-Jo ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 366~371
DOI : 10.9725/kstle.2013.29.6.366
Various heat treatment and surface coating methods have been applied to machine parts. Nowadays, diamond-like carbon (DLC) coatings are widely used because of their excellent tribological characteristics. Despite the numerous studies on DLC-coated engineering surfaces, the exact wear mechanisms related to the coating thickness and elastic modulus have not been fully examined. In this study, a sliding contact problem between a small spherical hard particle and a DLC-coated steel surface is analyzed using a nonlinear finite element code, MARC. The maximum principal stress distributions and deformed surfaces are compared for different coating thicknesses and Young`s modulus values. Plastically deformed surface shapes such as a groove and torus indicate that the most dominant wear mechanism for a DLC-coated surface is abrasive wear. Fatigue wear can also play a role in a case where the coating thickness is relatively large and the elastic modulus is high.
Fabrication of Embedded Thermocouple Sensor and Experimental Study on Measurement of Interface Temperature for Dry Friction
Jang, Beomtaek ; Lim, Youngheon ; Kim, Seocksam ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 372~377
DOI : 10.9725/kstle.2013.29.6.372
This study investigated the interface temperatures for the sliding friction of three types of pins fabricated with thermocouple wires by the suction casting method. Optical microscopy was used to examine the surrounding material state at the bonding interface with the thermocouple wires. Friction tests were performed under dry sliding conditions against stainless steel 304 at nominal stresses of 1.42-4.25 MPa and sliding speeds of 0.5-1.25 m/s. Tribological data were collected using a custom-made pin-on-disk apparatus that measured the interface temperature and corresponding friction coefficient. Static tests were performed to demonstrate the functionality and reliability of the thermocouple wires-combined temperature sensor (TCTS). Each TCTS showed good linearity and sensitivity and very similar response times for the thermocouple and critical temperature during sliding friction.
Analysis of Compliance of Planetary Gears based on Floating Intermediate Rings
Cho, Ihnsung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 378~385
DOI : 10.9725/kstle.2013.29.6.378
An epicyclic gearing system is compact and lightweight. However, it is difficult to share the driving force equally because the system has closed gear trains with multiple driving points, and it always has geometrical errors in the elements. Thus, in the case of planetary gears, the first problem is how to distribute the load evenly to the numerous planets. The method widely used abroad for this purpose is to utilize the elastic deformation of the components of the structure. However, the deflection is very complicated, and it is very easy for vibration problems to occur because of the decrease in the natural frequencies. Therefore, to equalize the load on the planets, this paper discusses the principle and theory behind the functioning of a floating intermediate ring. This magnifies the displacement of a planet`s center arising from the equilibrium of the load and the lubricating film pressure, which improves the compliance of the planets. The results show that load equalization of the planets is possible through this improvement in their compliance.
Design Analysis to Enhance Rotordynamic Stability of High-Speed Lightweight Centrifugal Compressor - Part I: Effects of Bearing Designs
Lee, An Sung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 386~391
DOI : 10.9725/kstle.2013.29.6.386
Part I of this study analyzed the effects of tilting pad bearing designs to reduce the stiffness of the bearings used in a process high-speed lightweight centrifugal compressor intended for a domestic refinery use. This was done in an attempt to enhance the robustness of its rotordynamic stability against possible aerodynamic cross-coupled stiffness. The bearing design variables reviewed were the clearances, LBPs, LOPs, and preloads. The results showed that there was practically no difference between the LBP and LOP designs in terms of the bearing stiffness, because the compressor rotor was lightweight and the bearings had relatively high preloads. Increasing both the machined and assembled clearances in bearing designs has resulted in the bearing stiffness being greatly reduced. In addition, it has been confirmed that an additional reduction in the bearing stiffness can be obtained for given fixed machined clearances by decreasing the preloads, i.e., by increasing the assembled clearances.
Synthesis of Antioxidant and Evaluation of Its Oxidation Stability for Biodiesel
Park, Soo-Youl ; Shin, Seung-Rim ; Shin, Joung-II ; An, Kyoung-Lyong ; Jun, Kun ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 392~396
DOI : 10.9725/kstle.2013.29.6.392
Biodiesel fuels contain unsaturated fatty acid ester, which can easily oxidize, especially when exposed to ultraviolet light. The products formed by this oxidation give rise to sediment or gum formation. As a result, the fuel can contribute to the corrosion and plugging of the filter pump. Antioxidants have been used in an effort to stabilize biodiesels, but there is still a need for a biodiesel composition with improved oxidation stability. In general, good fuel compositions should provide synergistic combinations of a biodiesel and antioxidants. Our work involved the synthesis of antioxidants to improve the oxidative stability of biodiesel fuel.
Failure Examples Study for Tribological Characteristics of Drive Shaft and Axle System in Vehicles
Lee, Il Kwon ; Moon, Hak Hoon ; Youm, Kwang Wook ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 6, 2013, Pages 397~402
DOI : 10.9725/kstle.2013.29.6.397
This study examined the tribological characteristics of the drive shaft and axle system in vehicles. The first drive shaft example contained end play for a CV joint that transferred part of the transmission power to the wheel. The joint part of the drive shaft was deformed because of reduced durability due to wear. Thus, vibrations caused the body to shake and become unbalanced when the drive shaft transferred the power. The second example was the cross-section of a shaft that connected the slip-connection of the propeller shaft on the input side to the yoke flange of the output side; the durability was reduced because of corrosion. End play caused by wear between the bearing and cross-section shaft appeared to cause shaking. In the third example, a grease leak reduced lubrication and thus caused damage to the hub bearing and inside the knuckle. The failure was produced by sticking. The fourth example had noise produced by the gear and gear transfer. This was due to the backlash of the pinion and few ring gears for the differential gear. Therefore, drive shaft and axle systems must be thoroughly checked and managed to minimize and reduce failure phenomena.