• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.106-114
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• 1998

Tribological investigation of ultra thin film magnetic storage disks which have two different kinds of start/stop zone of laser textured bump disk and mechanically textured disk for before CSS test and after CSS test. To measure surface roughness, height reduction before/after CSS test and obtain accurate topographies, AFM(Atomic Force Microscope) which is most powerful recently has been used. The result of statistical analysis showed that both laser textured bump height and mechanically textured zone height have been reduced about 4~7nm after 15000 cycle CSS test. Using commercial Nano-Indenter, ramping load scratch test has been performed to investigate friction characteristic for laser textured zone and mechanically textured zone before/after CSS test.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.183-190
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• 1997

The wear behaviors of $Al_2O_3-40%TiO_2$ deposited on casting aluminum alloy(ASTM A356) by plasma spray against SiC ball have been investigated experimentally. Friction and wear tests are carried out at room temperature. The friction coefficient of $Al_2O_3-40%TiO_2$ coating is lower than that of pure $Al_2O_3$ coating(APS). It is found that low friction correspond to low wear and high friction to high wear in the experimental result. The thickness of $Al_2O_3-40%TiO_2$ coatings indicated the existence of the optimal coating thickness. It is found that a voids and porosities of coating surface result in the crack generated. As the tensile stresses in coating increased with the increased friction coefficient. The columnar grain of coating will be fractured to achieve the critical stress. It is found that the cohesive of splats and the porosity of surface play a role in wear characteristics. It is suggested that the mismatch of thermal expansion of substrate and coating play an important role in wear performance. Tensile and compressire under thermo-mechanical stress may be occurred by the mismatch between thermal expansion of substrate and coating. This crack propagation above interface is observed in SEM.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 한국윤활학회 1987년도 제5회 학술강연회초록집
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• pp.50-56
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• 1987

A mechanical face seal is most commonly used to seal liquids and gases at various speeds, pressures and temperatures. The primary seal ring is in sliding contact with the seal seat and as a result heat in the vicinity of the interface is generated. Local temperatures at points along the circumferential direction will fluctuate as asperities on the surfaces pass. This kind of fluctuation of temperature has been investigated to take place. This may lead to the hot spots phenomenon between the contacting asperities. Sibley and Allen showed photographic evidence of systemically moving hot spots in the contact zone. The appearance of such a temperature disturbance has been attributed to a kind of thermoelastic instabilities between two surfaces: This involves a feedback loop which comprises localized elevation of frictional heating, resultant localized thermal bulding, localized pressure increase as the result of the bulging and futher elevation of frictional heating as the result of the pressure increase. The heating of hot spots will be continued until the expanded material due to the frictional heating is worn off. Therefore to predict the speed of temperature propagation into the body is essential to the analysis of heat transfer on the edge of the seal.

• KSTLE International Journal
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• 제1권1호
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• pp.12-20
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• 2000

Nano-wear and friction of carbon overcoated laser-textured and mechanically-textured computer hard disk were characterised after contact start/stop (CSS) wear test. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties and friction characteristics of the coating arising from the contact start/stop wear test These techniques include: the atomic force microscopy (AFM), the continuous nano-indentation test, the nano-scratch test, the time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and the auger electron spectroscopy (AES). It was shown that the surface roughness of the laser-textured (LT) bump and mechanically textured (MT) Bone was reduced approximately am and 7nm, respectively, after the CSS wear test. The elastic modulus and hardness values increased after the CSS test, indicating straining hardening of the top coating layer, A critical load was also identified fer adhesion failure between the magnetic layer and the Ni-P layer, The TOF-SIMS analysis also revealed some reduction in the intensity of C and $C_2$$F_59$, confirming the wear of lubricant elements on the coating surface.

• Tribology and Lubricants
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• 제39권2호
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• pp.49-55
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• 2023

Currently, the demand for green technologies toward a sustainable future is rapidly increasing due to growing concern over environmental issues. Methanol is biodegradable and can provide clean combustion to reduce sulfur oxide and nitrogen oxide emissions, and therefore it is a candidate fuel for marine engines. However, the effect of methanol on tribological characteristic degradation should be addressed for methanol-fueled engines. In this study, the methanol addition effects on tribological characteristic degradation is experimentally assessed using a pin-on-disk tribo-tester. Ni-based alloy is used as a target material due to its broad applicability as an engine component material. For a lubricant, engine oil with and without methanol are used. The tests are conducted for up to 10,000 cycles under boundary lubrication while the change in friction force is monitored. Additionally, the wear rate is determined based on laser scanning confocal microscope data. An additional test in which methanol is added at regular intervals is performed with an aim to directly observe its effect on friction. Overall, the friction coefficient increases slightly with increasing methanol concentration. Furthermore, the wear rate of the pin and disk increase significantly with methanol addition. The results also indicate that the friction increases instantaneously with methanol addition at the contacting interface. These findings may be useful for better understanding the methanol effect on the tribological characteristics of Ni-based alloys for methanol-fueled engines with improved performance.