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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 28, Issue 6 - Dec 2012
Volume 28, Issue 5 - Oct 2012
Volume 28, Issue 4 - Aug 2012
Volume 28, Issue 3 - Jun 2012
Volume 28, Issue 2 - Apr 2012
Volume 28, Issue 1 - Feb 2012
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Journal Bearing Design Retrofit for Process Large Motor-Generator - Part II : Rotordynamics Analysis
Lee, An Sung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 265~271
DOI : 10.9725/kstle-2012.28.6.265
In the preceding Part I study, for improving the unbalance response vibration of a large PRT motor-generator rotor fundamentally by design, a series of design analyses were carried out for bearing improvement by retrofitting from original plain partial journal bearings, applied for operation at a rated speed of 1,800 rpm, to final tilting pad journal bearings. To satisfy evenly key basic lubrication performances such as the minimum lift-off speed and maximum oil-film temperature, a design solution of 5-pad tilting pad journal bearings and maximizing the direct stiffness by about two times has been achieved. In this Part II study, a detailed rotordynamic analysis of the large PRT motor-generator rotor-bearing system will be performed, applying both the original plain partial journal bearings and the retrofitted tilting pad journal bearings, to confirm the effect of rotordynamic vibration improvement after retrofitting. The results show that the rotor unbalance response vibrations with the tilting pad journal bearings are greatly reduced by as much as about one ninth of those with the plain partial journal bearings. In addition, for the tilting pad journal bearings there exist no critical speed up to the rated speed and just one instance of a concerned critical speed around the rated speed, whereas for the plain partial journal bearings there exist one instance of a critical speed up to the rated speed and two instances of concerned critical speeds around the rated speed.
Study on Within-Wafer Non-uniformity Using Finite Element Method
Yang, Woo Yul ; Sung, In-Ha ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 272~277
DOI : 10.9725/kstle-2012.28.6.272
Finite element analysis was carried out using wafer-scale and particle-scale models to understand the mechanism of the fast removal rate(edge effect) at wafer edges in the chemical-mechanical polishing process. This is the first to report that a particle-scale model can explain the edge effect well in terms of stress distribution and magnitude. The results also revealed that the mechanism could not be fully understood by using the wafer-scale model, which has been used in many previous studies. The wafer-scale model neither gives the stress magnitude that is sufficient to remove material nor indicates the coincidence between the stress distribution and the removal rate along a wafer surface.
Analysis of Fluid Flow Characteristics Around Rolling Element in Ball Bearings
Jo, Jun Hyeon ; Kim, Choong Hyun ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 278~282
DOI : 10.9725/kstle-2012.28.6.278
Various bearings such as deep-groove ball bearings, angular-contact ball bearings, and roller bearings are used to support the load and to lubricate between the shaft and the housing. The bearings of potential rolling systems in a turbo pump are the deep-groove ball bearings as comparing with the bearings with rolling elements such as cylindrical rollers, tapered cylindrical rollers, and needle rollers. The deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway and a retainer that maintain separation and help to lubricate the rolling element that is rotating in the raceways. In the case of water-lubricated ball bearings, however, fluid friction between the ball and raceways is affected by the entry direction of flow, rotation speed, and flow rate. In addition, this friction is the key factor affecting the bearing life cycles and reliability. In this paper, the characteristics of flow conditions corresponding to a deep-groove ball bearing are investigated numerically, with particular focus on the friction distribution on the rolling element, in order to extend the analysis to the area that experiences solid friction. A simple analysis model of fluid flow inside the water-lubricated ball bearing is analyzed with CFD, and the flow characteristics at high rotation speeds are presented.
Sliding Contact Analysis of a Spherical Particle between Rubber Seal and Coated Steel Counterface
Park, Tae-Jo ; Lee, Jun-Hyuk ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 283~288
DOI : 10.9725/kstle-2012.28.6.283
In this study, a new sliding contact problem involving an elastomeric seal, a spherical particle and a hard coated steel counterface was modeled to investigate the detailed wear mechanisms related to the sealing surface. The model was also used to design the optimum coating conditions. A three-dimensional finite element contact problem was modeled and analyzed using the nonlinear finite element code, MARC. The deformed steel surface and stress distributions are presented for different coating layers and thicknesses. When the coating thickness is relatively small, the entrapped particle produces surface plastic deformations such as groove and torus. In addition, the sealing surface can be damaged by abrasive wear as well as fatigue wear. For a relatively thick and multi-layered coating, on the other hand, surface plastic deformation does not occur, and the amount of abrasive and fatigue wear is reduced. Therefore, the proposed contact model and results can be used in the design of various sealing systems, further intensive studies are required.
Effect of Contact Stiffness on Lateral Force Calibration of Atomic Force Microscopy Cantilever
Tran, Da Khoa ; Jeon, Ki-Joon ; Chung, Koo-Hyun ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 289~296
DOI : 10.9725/kstle-2012.28.6.289
Atomic force microscopy (AFM) has been used for imaging surfaces and measuring surface forces at the nano-scale. Force calibration is important for the quantitative measurement of forces at the nano-scale using AFM. Normal force calibration is relatively straightforward, whereas the lateral force calibration is more complicated since the lateral stiffness of the cantilever is often comparable to the contact stiffness. In this work, the lateral force calibrations of the rectangular cantilever were performed using torsional Sader's method, thermal noise method, and wedge calibration method. The lateral optical lever sensitivity for the thermal noise method was determined from the friction loop under various normal forces as well. Experimental results showed that the discrepancies among the results of the different methods were as large as 30% due to the effect of the contact stiffness on the lateral force calibration of the cantilever used in this work. After correction for the effect of contact stiffness, all the calibration results agreed with each other, within experimental uncertainties.
3D Elastic Contact Analysis of Sharkskin Surface Pattern
Kim, Tae Wan ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 297~302
DOI : 10.9725/kstle-2012.28.6.297
We conducted 3D elastic contact analysis of a sharkskin surface pattern for the characteristic assessment of biomimetic shark skin structure pattern for engineering applications. Rough sharkskin surfaces of similar size with real shark skin scales are generated numerically. Under the assumption of the contact of a plate on the generated sharkskin surface, contact performances such as contact pressure, real contact area, and surface separation are evaluated.
A Study on the Lubrication Characteristics of Spool Valve with Spiral Groove
Hong, Sung-Ho ; Son, Sang-Ik ; Kim, Kyung-Woong ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 303~314
DOI : 10.9725/kstle-2012.28.6.303
In this research, spool valves with spiral grooves are suggested and their lubrication characteristics are investigated by numerical analysis. The three-dimensional flow field is obtained by solving the Navier-Stokes equations in dimensionless form, so that the performance variables such as lateral force, friction force and volume flow rate are determined. Also, the lubrication characteristics of spool valves with spiral grooves are compared with those with typical grooves under variable working conditions. It is shown that spool valves with spiral grooves can get better performance in aspect of mitigation of uneven pressure distribution surrounding spool. Moreover, it is found that the minimum distance between spool edges and grooves, the type of spiral groove, and the groove angle have noticeable effect on the lubrication characteristics.
GC/MS Analysis of Ethylene Glycol in the Contaminated Lubricant Oil Through Solvent Extraction Followed by Derivatization using Bistrimethylsilyltrifluoroacetamide (BSTFA)
Lee, Joon-Bae ; Kwon, O-Seong ; You, Jae-Hoon ; Shon, Shungkun ; Sung, Tae-Myung ; Paeng, Ki-Jung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 315~320
DOI : 10.9725/kstle-2012.28.6.315
For proper functioning, general machines usually need lubricant oil as a cooling, cleaning, and sealing agent at points of mechanical contact. The quality of lubricant oil can deteriorate during operation owing to various causes such as high temperature, combustion products and extraneous impurities. In this study, a heavy load stopped during operation, and the oil was analyzed to check whether any impurities were added. Extraction using acetonitrile followed by reaction with BSTFA(bistrimethylsilyl trifluoroacetamide) showed that, trimethylsilylated ethylene glycol was present in the lubricant oil. To quantify the ethylene glycol in the oil, deuterium-substituted ethylene glycol, which acted as an internal standard, was added to the sample and then extracted with the solvent. Next, the extract was reacted with the derivatizing agent(BSTFA) and then analyzed with GC/MS. The detection limit of this method was found to be
and the recovery of oil containing
of ethylene glycol was measured to be 94.8%. A damaged O-ring and eroded cylinder liner were found during the overhaul, which implied the leakage of coolant containing ethylene glycol into the lubricating system. The erosion of the cylinder liner was assumed to be due to cavitation of the coolant in the cooling system.
Lubricity Characterization of Hydrogenated Biodiesel as an Alternative Diesel Fuel
Kim, Jae-Kon ; Jeon, Cheol-Hwan ; Yim, Eui-Soon ; Chung, Choong-Sub ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 321~327
DOI : 10.9725/kstle-2012.28.6.321
Paraffin bio-based hydrotreated biodiesel(HBD) is originated from vegetable oil(the process can also be applied to animal fat) with the the chemical structure
. In the number of process of the oil or fat, the hydrogenation is significantly important to create a bio-based diesel fuel. This study is focused on lubricity characteristics of BTL diesel blends to use alternative diesel fuel in Korea. The BTL diesel are blended the different volume ratios (HBD 5(5 vol.% HBD - 95 vol.% diesel), HBD 10, HBD 20, HBD 30, HBD 40 and HBD 50. HBD with paraffin compounds showed a very high centane number, low sulfur content and free aromatic compound. Especially, the wear scar of HBD showed poor lubricity compared to automotive diesel due to the fuel composition, low sulfur content and free aromatic compound. Also, the lubricity specification of automotive diesel with different six HBD blends is within the limit by the Korean standards. Finally, HBD as an alternative diesel fuel is challengeable in transportation sector of Korea.
Development and Verification of Measuring Tester for Generated Axial Force at Constant Velocity Joints
Lee, Kwang-Hee ; Lee, Deuk-Won ; Lee, Chul-Hee ; Yun, Hyuk-Chae ; Cho, Won-Oh ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 328~332
DOI : 10.9725/kstle-2012.28.6.328
Generated Axial Force (GAF) due to internal friction at Constant Velocity (CV) joints is one of the causes generating vibration problems such as shudder in vehicle. In this study, the GAF measuring tester is developed to precisely measure GAF caused by internal friction in CV joints. As the developed tester can control temperature at joint, driving torque, angle of rotation and joint angles, actual driving conditions such as sudden acceleration can be applied to the machine. GAFs are measured and compared by using different types of grease in tripod housing. Also GAFs are measured for both new and used CV joints to be compared and analyzed. The test result shows the repeatability and consistency of the tester in terms of the different test conditions. By using the developed CV joint tester, friction performance of the joint can be evaluated by proposing the best CV joints as well as greases generating the lowest GAF.
Friction and Wear Properties of Improved Polyurethane Based Magneto-Rheological Elastomer
Lian, Chenglong ; Hong, Sung-Geun ; Lee, Kwang-Hee ; Lee, Chul-Hee ; Kim, Cheol-Hyun ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 28, issue 6, 2012, Pages 333~339
DOI : 10.9725/kstle-2012.28.6.333
Typical magneto-rheological (MR) elastomers consist of silicon-based material. A number of studies have been carried out to evaluate the vibration and tribological characteristics of silicon-based MR e-lastomers. However, these elastomers have quite low strength, so they have low wear resistance. In this study, polyurethane-based MR elastomers with performances better than those of MR elastomers. Experiments have been conducted on different MR elastomers (Pu MR elastomer, Pu-Si MR elastomer, and Pu-wrapped-Si MR elastomer) and different predefined magnetic directions (Non-Direction, Vertical Direction, and Horizontal Directionality) to evaluate the friction and wear performance under a magnetic field. The results show that Pu-wrapped-Si MR elastomer with a horizontal predefined magnetic field has the best performance in terms of wear.