• Title/Summary/Keyword: tribology tests

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Evaluation of Wear Performance of Corroded Materials in an 800℃ Molten Salt Environment (800℃ 용융염 환경에서 부식된 재료의 마모 성능 평가)

  • Yong Seok Choi;Kyeongryeol Park;Seongmin Kang;Unseong Kim;Kyungeun Jeong;Ji Ha Lee;Tae Woong Ha;Kyungjun Lee
    • Tribology and Lubricants
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    • v.40 no.3
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    • pp.97-102
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    • 2024
  • The next-generation Molten Salt Reactor is known for its high safety because it uses nuclear fuel dissolved in high-temperature molten salt, unlike traditional solid atomic fuel methods. However, the high-temperature molten salt causes severe corrosion in internal structural materials, threatening the reactor's safety. Therefore, it is crucial to investigate the high-temperature corrosion resistance and wear performance of materials used in reactors to ensure safety. In this study, the high-temperature corrosion resistances and wear performances of corrosion samples in a NaCl-MgCl2-KCl (20-40-40 [wt%]) molten salt are investigated to evaluate the applicability of economically viable stainless steels, 316SS and 304SS. Hastelloy C276 and a new alloy containing a small amount of Nb are used as reference samples for comparative analysis. The mass loss, mass loss rate per unit volume, and surface roughness of each sample are measured to understand the corrosion mechanisms. Scanning electron microscopy and energy-dispersive spectroscopy analyses are employed to analyze the corrosion mechanisms. Wear tests on the corroded samples are also conducted to assess the extent of corrosion. Based on the experimental results, we predict the lifespans of the materials and evaluate their suitability as candidate materials for molten salt reactors. The data obtained from the experiments provide a valuable database for structural materials that can enhance the stability of molten salt reactors and recommend high-temperature corrosion-resistant materials suitable for next-generation reactors.

Friction Characteristics of DLC and WC/C (DLC와 WC/C의 마찰특성)

  • Kim, Dong-Wook;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • v.27 no.6
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    • pp.308-313
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    • 2011
  • In this study, friction tests were performed in order to investigate the effect of sliding velocity and normal load on the friction characteristics of DLC (a-C:H) and WC/C (a-C:H:W) using a ball-on-disk type friction tester. DLC and WC/C were deposited on AISI 52100 steel balls. Friction tests against carburized SCM 415 Cr-Mo steel disks were carried out under various sliding velocity (0.1, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mm/s) and normal load (2.4, 4.8 and 9.6 N) conditions while the relative humidity was 20~40 % R.H. and air temperature was $16{\sim}24^{\circ}C$. As results, kinetic friction coefficients of DLC and WC/C were obtained under each test condition. The results show that the kinetic friction coefficients of DLC and WC/C generally increase with the increase in sliding velocity. And, under the same sliding velocity condition, the kinetic friction coefficients are almost constant regardless of normal load. In addition, the kinetic friction coefficients of DLC are lower than those of WC/C under the same test conditions.

Rotordynamic Performance Measurements and Predictions of a FCEV Air Compressor Supported on Gas Foil Bearings (가스 포일 베어링으로 지지되는 연료전지 전기자동차용 공기압축기의 회전체동역학적 성능 측정 및 예측)

  • Hwang, Sung Ho;Moon, Chang Gook;Kim, Tae Ho;Lee, Jongsung;Cho, Kyung Seok;Ha, Kyoung-Ku;Lee, Chang Ha
    • Tribology and Lubricants
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    • v.35 no.1
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    • pp.44-51
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    • 2019
  • The paper presents the rotordynamic performance measurements and model predictions of a fuel cell electric vehicle (FCEV) air compressor supported on gas foil bearings (GFBs). The rotor has an impeller on one end and a thrust runner on the other end. The front (impeller side) and rear (thrust side) gas foil journal bearings (GFJBs) are located between the impeller and thrust runner to support the radial loads, and a pair of gas foil thrust bearings are located on both sides of the thrust runner to support the axial loads. The test GFJBs have a partial arc shim foil installed between the top foil and bump strip layers to enhance hydrodynamic pressure generation. During the rotordynamic performance tests, two sets of orthogonally installed eddy-current displacement sensors measure the rotor radial motions at the rotor impeller and thrust ends. A series of speed-up and coast-down tests to 100k rpm demonstrates the dominant synchronous (1X) rotor responses to imbalance masses without noticeable subsynchronous motions, which indicates a rotordynamically stable rotor-GFB system. Finite element analysis of the rotor determines the rotor free-free (bending) natural modes and frequencies well beyond the maximum rotating frequency. The predicted damped natural frequencies and damping ratios of the rotor-GFB system reveal rotordynamic stability over the speeds of interest. The imbalance response predictions show that the predicted critical speeds and rotor amplitudes strongly agree with the test measurements, thus validating the developed rotordynamic model.

The Effect of Corrosion of Rolling Bearing Ceramics in Alkalic Solution on the Rolling Wear and Hardness (알카리용액에서 구름베어링용 세라믹스의 부식이 구름마모 및 경도에 미치는 영향)

  • 최인혁;김상근;박창남;윤대현;신동우
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.11a
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    • pp.154-159
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    • 1999
  • Silicon nitride ceramic has been verified as an excellent rolling bearing material because of its high strength and outstanding rolling fatigue life properties. However under some corrosive circumstances it showed drawbacks such as hardness reduction and severe wear caused by corrosion. In this work, the variations of the rolling wear and hardness of three kinds of ceramics were studied for the specimen aged 15 days in alkali water (90$\pm$2$^{\circ}C$, 25 wt% NaOH). All of the specimens, \circled1Si$_3$N$_4$, \circled23Y-TZP and \circled33Y-TZP alloyed with 5 wt% CeO$_2$, were sintered and post-Hipped, and then polished up to 0.02 ${\mu}{\textrm}{m}$Ra of surface roughness. Rolling wear tests were conducted by MJ type rolling fatigue life tester under the initial theoretical maximum contact stress or 3.76 Gra and the spindle speed of 1,000 rpm. Spindle oil was used as a lubricant. The specimens were not worn before aging. For the specimen aged in alkali water, Si$_3$N$_4$and 3Y-TZP were worn by rolling wear tests, and hardness was decreased. While aging the specimens, the phase was transformed from tetragonal to monoclinic in 3Y-TZP and the microstructure change occurred in Si$_3$N$_4$. 3Y-TZP alloyed with 5 wt% CeO$_2$specimens were not worn after aging and no phase transformation occurred while aging.

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Friction transition diagram considering the effects of oxide layer formed on contact parts of TiN coated ball and steel disk in sliding (TiN코팅된 볼과 스틸디스크의 미끄럼운동 시 접촉면에 형성되는 산화막의 영향을 고려한 마찰천이선도 작성에 대한 연구)

  • 조정우;박동신;임정순;이영제
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.109-116
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    • 2001
  • In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to form the oxide layer and the characteristics of the oxide layer formation are investigated. AIS152100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4um in coating thickness. AISI1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitride environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

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Variations in Tribology Factors of SM45C by UNSM Modification (SM45C재의 UNSM 처리에 의한 트라이볼러지 특성 변화)

  • Shim, Hyun-Bo;Suh, Chang-Min;Suh, Min-Soo;Amanov, Auezhan;Pyun, Young-Sik
    • Journal of Ocean Engineering and Technology
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    • v.32 no.6
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    • pp.492-501
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    • 2018
  • The following results were obtained from a series of studies to accumulate data to reduce the coefficient of friction for press dies by performing tribological tests before and after the UNSM treatment of SM45C. The UNSM-treated material had a nano-size surface texture, high surface hardness, and large and deep compressive residual stress formation. Even when the load was doubled, the small amount of abrasion, small weight of the abrasion, and width and depth of the abrasion did not increase as much as those for untreated materials. When loads of 5 N, 7.5 N, and 10 N were applied to the untreated material of SM45C, the coefficient of friction was approximately 0.76-0.78. With the large specimen, a value of 0.72-0.78 was maintained at a load of 50 N despite the differences in the size of the wear specimen and working load. Tribological tests of large specimens of SM45C treated with UNSM under tribological conditions of 100 N and 50 N showed that the frictional coefficient and time constant stably converged between 0.7 and 0.8. The friction coefficients of the small specimens treated with UNSM showed values between 0.78 and 0.75 under 5 N, 7.5 N, and 10 N. The friction coefficients of the SM45C treated with UNSM were comparable to each other.

Tribology Characteristics of Hexagonal Shape Surface Textured Reduction Gear in Electric Agricultural Vehicle

  • Choi, Wonsik;Pratama, Pandu Sandi;Byun, Jaeyoung;Kwon, Soonhong;Kwon, Soongu;Park, Jongmin;Kim, Jongsoon;Chung, Songwon
    • Journal of the Korean Society of Industry Convergence
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    • v.22 no.1
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    • pp.47-54
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    • 2019
  • An experimental study was conducted on the wear and friction responses in sliding tests of a micro-textured surface on laser pattern (LP) steel as reduction gear material in electric guided vehicle. In this research, the friction characteristics of laser pattern steel under different micro texture density conditions were investigated. The friction tests were carried out at sliding speeds of 0.06 m/s to 0.34 m/s and at normal loads of 2 to 10 N. Photolithography method was used to create the dimples for surface texturing purpose. Four different specimens having different dimple densities of 10%, 12.5%, 15%, and 20% were observed respectively. In this research, friction conditions as shown in Stribeck curve were investigated. Furthermore, the microscopic surface was observed using scanning electron microscope. It was found that the dimple density had a significant role on the friction characteristics of laser pattern steel conditioned as reduction gear material in an agricultural vehicle. The duty number showed that the friction condition was hydrodynamic regime. The best performance was obtained from 12.5% dimple density with lowest friction coefficient achieved at 0.018771 under the velocity of 0.34 m/s and 10N load.

Tribological performance of some organic fluorine-containing compounds as lubricants

  • Liu, Weimin;Ye, Chengfeng;Xue, Qunji
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.349-350
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    • 2002
  • The friction and wear behaviors of fluorine-containing compounds such as perfluoropolyethers (PFPE), phosphazenes (X-1P), ionic liquids as lubricants for steel/seel, steel/ceramic, ceramic/ceramic were investigated using a SRV tester and a one-way reciprocating friction tester both in ball-on-disc configuration. It was found that the three fluorine-containing lubricants could reduce friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as ionic liquids>X-1P>PFPE. Tests also showed that aryloxyphosphazene with polar substituent as a lubricant of steel/steel pair gave low wear, while aryloxyphosphazene with nonpolar group on the phenyl pendant led to high wear. The morphology and the tribo-chemical reaction of the worn surfaces were analyzed with a scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). XPS analyses illustrated the formation of iron fluoride in steel/steel system with the lubrication of both phosphazenes and ionic liquids.

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A Study of Magnetic Fluid Seals for Blood Sealing

  • Tomioka, Jun;Fukaishi, Akira;Ohba, Takashi
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.373-374
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    • 2002
  • Magnetic fluid seals are used in a wide variety of gas and dust sealing applications. However, it is difficult to seal for liquid because of its characteristic. This study will be a basic guide for a magnetic fluid seal for liquid, especially for blood to be practically used in medical instruments such as rotary blood pumps by clarifying its seal properties. Sealing pressure test, durability test, and hemolysis test have been conducted for this seal. In this study, magnetic fluid, sealing fluid, eccentricity ratio, revolution speed were selected as parameters. As results of the tests, it has been found that the properties of magnetic fluid seal depend on the solvent and the saturation magnetization of magnetic fluid. Therefore, the selection of magnetic fluid is important for this seal. It also has been found that eccentricity ratio of the shaft caused harmful effect for seal properties. In conclusion, it has been showed that magnetic fluid seals could be possibly used in medical instruments such as blood pumps when blood come in contact with magnetic fluids.

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An Experimental Study on Improved Fuel Economy and Lower Exhaust Emissions of New Automotive Engine adopting Split Cooling System

  • Oh, C.S.;Lee, J.H.;Shin, S.Y.;Kim, W.T.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.407-408
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    • 2002
  • This paper presents a split cooling system for a new inline 4-cylinder automotive engine. The split cooling system circulates coolant to the cylinder head and cylinder block separately. The coolant flow in the cylinder block is controlled by a $2^{nd}$ Thermostat installed at the outlet of cylinder block. The $2^{nd}$ thermostat closes when the coolant temperature is low. And this makes the coolant flow in cylinder block nearly stagnant, thereby reducing the coolant-side heat transfer coefficient and raising cylinder bore temperature. The $2^{nd}$ thermostat starts to open when the coolant temperature reaches a specified temperature. The test results on engine dynamometer show improved fuel economy and lower exhaust emission which result from the decrease in friction works and cooling loss. Also, several vehicle tests, with application of the new engine have been performed. Fuel economy improvement of 0.5{\sim}2.0%$ yields from different test modes and details are discussed in this paper.

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