• Journal of the Korean Applied Science and Technology
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• v.26 no.2
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• pp.213-223
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• 2009

Conventional additives were added to a newly synthesized base oil to create synthetic lubricants. Commercial polyol ester prepared in this laboratory were obtained as esterification of 1,1,1-trimethylol propane and respectively. This newly synthesized base oil had a variable chemical structure that could achieved the following properties; oxidation or thermal stability, low temperature fluidity, and higher flash points. When compared with commercial mineral lubricants, the synthetic lubricants show superior thermal and oxidation stability, and anti-wear properties.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.10-17
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• 2003

The amount of production orders from Japanese car and construction machine industries have slightly increased in 2002, but the costs of the forged parts have decreased due to severe competitions with the other Asian countries. Most of the forging industries and some universities are making more efforts for technological researches and developments to meet the demand for higher accuracy and higher quality products, shortening of delivery time, and development of forged parts for new industrial fields. Some helical gears of which surfaces can be net-shaped have been started for commercial base production to be shipped to car industries. Some non-graphite lubricants for hot forging and some conversion coating free lubricants for cold forging have been developed to improve some environmental problems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.195-198
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• 2006

Zinc phosphate coating is required in nearly all steel cold forging operations. However, the chemical byproducts of this lubricant system are difficult to dispose of and have a negative environmental impact. In order to replace zinc phosphate based lubricants partially or completely, candidate lubricant has been developed in this study. The performance evaluation of these lubricants was conducted using the double cup extrusion test and spike forging test. With the use of the commercial FEM code DEFORM, friction factor calibration curves, i.e. cup height ratio vs. punch stroke and spike height vs. punch stroke, were established for different friction factor values. By matching the cup height ratio and the punch stroke and spike height vs. punch stroke from experiment to that obtained from FE simulations, the friction factor of the lubricants was determined. Three water-soluble lubricants; namely, Mec Homat, Royalcoat, and the developed lubricant were found to perform comparable to or better than zinc phosphate.

• Tribology and Lubricants
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• v.18 no.4
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• pp.255-259
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• 2002

The tribological properties of eight different liquid crystals were investigated in a concentrated point contact device and a ball-on-flat contact. For comparison, the same tests were also performed with commercial greases and the corresponding base oils. Under the fully flooded conditions studied, liquid crystals in a concentrated point contact showed lower friction than commercial greases and greater film thickness dependence on rolling speed than grease base oils or greases. Test results also showed that the film thickness and friction were little influenced by the composition of the examined liquid crystals.

• Journal of Mechanical Science and Technology
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• v.17 no.9
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• pp.1276-1286
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• 2003

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of 3％ were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.

• Tribology and Lubricants
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• v.36 no.6
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• pp.342-349
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• 2020

The rapidly increasing threats to the environmental has increased the demand for biodegradable lubricants. Vegetable oils, such as olive, coconut, and sunflower oils, are readily obtainable and are not harmful, unlike synthetic and mineral oils. The tribological characteristics of these oils should be adequately examined for industrial applications. In this study, the lubrication characteristics of olive oil is investigated using a pin-on-disk-type tribometer under 500 gf of normal force, and the examination results are compared and analyzed with those of commercial synthetic lubricants for friction and wear. In addition, stearic acid, which is a type of saturated fatty acid, is mixed with olive oil as an additive to improve its lubrication characteristics. Olive oil with stearic acid additive is thus observed to exhibit the lowest friction coefficient for rotational speeds of 200 to 800 rpm. According to the wear analysis, a minimal amount of wear is observed when no additive is used. Hence, olive oil is able to effectively reduce friction and wear at relatively low speeds. These low friction and wear characteristics of olive oil are attributed to its compatibility with the substrate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.263-264
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• 2002

The tribological characteristic of several environmentally friendly lubricating base stocks was examined, and the effect of some commonly used additives on th tribological behavior of the lubricating oils was comparatively investigated on a four-ball machine. It has been found that the commercial additives including butene sulfide, wax chloride, zinc dialkyldithiophosphate and ashless P-N type agent helped to improve the friction-reducing and antiwear properties as well as the extreme pressure behavior. Non-toxic nanoscale $(CF)_x$ showed the best friction-reducing ability, though it registered relatively poor extreme pressure properties. The mechanism on friction of nano-scale material is discussed.

• Tribology and Lubricants
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• v.29 no.5
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• pp.291-297
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• 2013

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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.16-23
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• 2021

Pin-to-disc wear testing experiments were conducted to investigate the wear characteristics of commercial oil (5W-40) with nano-diamond particles. The upper specimen was a SUJ-2 high-carbon chromium steel ball with a diameter of 4 mm, and the lower specimen was made of the Al-6061 alloy. The applied load was 5 N, and the sliding speed was 0.25 m/s. The wear tests were conducted at a sliding distance of 500 m. The friction coefficients and wear rates of the Al-6061 specimens were tested using commercial oil with different nano-diamond concentrations ranging from 0 to 0.02 wt.%. The addition of nano-diamond particles to commercial oil reduced both the wear rate and coefficient of friction of the Al-6061 alloy. The use of nano-diamond particles as a solid additive in oil lubricants was found to improve the tribological behavior of the Al-6061 alloy. For the Al-6061 alloy, the optimal concentration was found to be 0.005 wt.% in view of the friction coefficient and wear rate. Further investigation is needed to determine the optimal concentration of nano-diamond particles for various loadings, sliding speeds, oil temperatures, and sliding distances.

• Tribology and Lubricants
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• v.8 no.1
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• pp.24-29
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• 1992

Friction and wear characteristics of gear oils added load carrying aditives, JS and DBP have been invesitigated using Shell Four Ball Tester and Cygnus and also compared with commercial gear oil. The Gear oil added DBP among them showed excellent friction and wear performances, which is deduced by action mechanism of additives. The surface analysis of the worn balls was conducted using an optical microscope.