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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society of Tribologists and Lubrication Engineers
Journal Basic Information
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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Comparative Study of the Navier-Stokes Equation & the Reynolds Equation in Spool Valve Analysis Considering Cavitation
Hong, Sung-Ho ; Son, Sang-Ik ; Kim, Kyung-Woong ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 275~285
DOI : 10.9725/kstle.2013.29.5.275
The Reynolds equation is commonly used to investigate the lubrication characteristics of a spool valve. However, the applicability of the Reynolds equation is questionable for analyzing a spool valve because cavitation often occurs in the grooves of the valve and the depth of a groove is much higher than the clearance in most cases. In this study, the validity of the Reynolds equation in the spool valve analysis is investigated by comparing the results obtained from the Reynolds equation and those obtained from the Navier-Stokes equation. The results are compared in terms of the lateral forces, friction forces, and volume flow rates (leakages). A significant difference of more than 20% is found in the lateral forces in cases where cavitation occurs and there are many grooves. Therefore, the Navier-Stokes equation should be used to investigate the lubrication characteristics of a spool valve when cavitation occurs and when the spool valve contains many grooves.
A Study on Setting of Torque for Compressor Jointing Bolt
Kong, Yu Sik ; Kim, Tae Wan ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 286~290
DOI : 10.9725/kstle.2013.29.5.286
When a threaded fastener is tightened, the torque-tension relationship is highly sensitive to two friction components: thread friction and head friction. In this study, we carried out friction experiments and analyses to determine the optimum clamping torque setting for bolt joints. First, we measured the coefficients of thread friction and head friction under the same running conditions of the bolt clamping process for lubricated and non-lubricated bolts. We also measured axial tension through bolt clamping tests using lubricated and non-lubricated bolts attached to a strain gauge. Finally, we compared the experiment and theoretical results.
Characteristics of Lightweight Hydraulic Directional Control Valve for Emergency Steering in Hybrid Electric Commercial Vehicles
Park, Kyungmin ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 291~297
DOI : 10.9725/kstle.2013.29.5.291
Hydraulic directional control valves actuated by solenoid are used to control emergency steering in general or hybrid electric commercial vehicles. In this study, a new lightweight hydraulic directional control valve was designed by flow and structural simulation, and was fabricated; the basic operation, pressure differentials, and inner leakage flow were evaluated experimentally. In the results, the new model showed comparable performance with an existing imported valve. New valve was 80% the weight of the existing valve and had few components. Installing this valve on a truck body is easier because of its compactness and small size.
Wear Behavior of Al/SiC Composites Fabricated by Thermal Spray Process (2) - Effect of Applied Load on Wear Behavior -
Lee, Kwang Jin ; Kim, Kyun Tak ; Kim, Yeong Sik ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 298~303
DOI : 10.9725/kstle.2013.29.5.298
In this work, the effect of applied load on the wear behavior of Al/SiC composites was studied. Al/SiC composites were fabricated following the thermal spray process. Dry sliding wear tests were performed on these composites under four different applied loads, i.e., 5, 10, 15, and 20 N. The wear behaviors of the composites under these applied loads were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Under applied loads of up to 15 N, the wear rates of Al/SiC composites decreased with an increase in the applied load because of the formation of an adhesion layer on the worn surface. However in the case of an applied load of 20 N, the wear rate was significantly high because the formation and fracture of the adhesion layer were repeated continuously. These results show that the wear behaviors of the tested composites are significantly influenced owing to the applied loads.
Wettability of Biomimetic Riblet Surface like Sharkskin
Kong, Yu Sik ; Kim, Tae Wan ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 304~309
DOI : 10.9725/kstle.2013.29.5.304
Shark skin has functionalities such as self-cleaning and antifouling; it also exhibits excellent drag reduction owing to a hierarchical structure of microgrooves and nanometer-long chain mucus drag reduction interfaces around the shark body. In this study, the wettability of a shark skin surface and its replicas are evaluated. First, a shark skin template is taken from a real shark. Then, shark skin replicas are produced directly from a shark skin template, using a micromolding technique. The quantitative replication precision of the shark skin replicas is evaluated by comparing the geometry of the shark skin template to the replica using 2D surface profiles. Contact angles at the solid-air-water interfaces are evaluated for the shark skin template and its replicas under two conditions: with and without hydrophobic coating. The results show that the microriblets on shark skin improve the hydrophobic feature and play a critical role in self-cleaning.
Performance of Non-starting Conditioning System using Thermoelectric Modules for Hybrid Heavy Trucks
Park, Kyungmin ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 310~317
DOI : 10.9725/kstle.2013.29.5.310
To reduce vehicle fuel consumption due to not only driving but also air conditioning, battery-operated non-starting conditioning systems with thermoelectric modules and without mechanical elements like compressors are being manufactured for use by hybrid heavy trucks in the near future. In this study, the voltage and current consumed by a thermoelectric module were measured to determine the required battery power, and the performance of the conditioning system with air temperature, and humidity of the inlet/outlet modules and inside/outside the cabin for a truck, was evaluated using experimental apparatus under actual conditions. The results showed that, the thermoelectric module can be continously operated for about 1.5 h using existing 24 V batteries. The coefficent of performance(COP) of the cooling and heating modes was calculated to be an average 0.8-1.32. As expected, the heating performance was 30% more efficient than the cooling performance, which is general characteristic of thermoelectric modules.
New Cooling System Design of BLDC Motor for Electric Vehicle Using Computation Fluid Dynamics Modeling
Vu, Duc Thuan ; Hwang, Pyung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 5, 2013, Pages 318~323
DOI : 10.9725/kstle.2013.29.5.318
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
rpm. The results also showed that CFD can be effectively used to simulate the heat transfer of BLDC motors.