• Tribology and Lubricants
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• v.39 no.6
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• pp.250-255
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• 2023

This study applies various surface patterns to minimize material loss in construction equipment that is subject to severe wear due to sand, such as the wear-resistant steel plates of dump trucks or the teeth of excavators. The relationship between surface morphology and wear behavior is investigated using PLA+ polymer to observe the effect of the surface pattern. Five types of samples - smooth, concave, convex, wavy concave, and wavy convex designs - are created using a 3D printer. A wear experiment is conducted for a duration of 3 h using 6.5 kg of abrasive particles. The mass loss of the samples after the experiment is measured to assess the extent of wear. Additionally, the surface morphology of the samples before and after the experiment is analyzed using SEM and confocal microscopy. The study results reveal that the smooth design exhibits the highest wear loss, whereas the concave and wavy concave designs show relatively lower wear loss. The convex and wavy convex designs exhibit varying contact areas with the abrasive particles depending on the surface pattern, resulting in different levels of wear. Furthermore, a comparison between the experimental results and DEM simulations confirms the observed wear trends. This study reveals the relationship between wear damage according to surface pattern shape and is expected to be of substantial help in the analysis of wear and tear on agricultural and heavy equipment.

• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.360-364
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• 2010

Most research groups used two analysis methods (spectroscopy and nanotribology) to measure the mechanical properties of nano-materials: NMR (Nuclear Magnetic Resonance), IR (Infrared Spectroscopy), Raman Spectroscopy as the spectroscopy method and AFM (Atomic Force MicroScope), EFM (Electrostatic Force Microscope), KFM (Kelvin Force Microscope), Nanoindenter as the nanotribological one. Among these, the nano-indentation technique particularly has been recognized as a powerful method to measure the elastic modulus and the hardness. However, this technique are prone to considerable measurement errors with pressure conditions during measurement. In this paper, we measured the change of elastic modulus and hardness of an Al single crystal with the change of load, hold, and unload time, respectively. We found that elastic modulus and hardness significantly depend on load, hold, and unload time, etc. As the indent time was shortened, the elastic modulus value decreased while the hardness value increased. In addition, we found that elastic modulus value was more sensitive to indent load, hold, and unload time than the hardness value. We speculate that measurement errors of the elastic modulus and the hardness originate from the residual stress during indenting test. From our results, the elastic modulus was more susceptible to the residual stress than the hardness. Thus, we find that the residual stress should be controlled for the minimum measurement errors during the indenting test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.448-454
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• 2000

This study was undertaken to investigate tribological characteristics with atmospheric pressure for three alumina ceramics of different purity, such as, 85 %, 95 % and 99.7 %. The wear test was carried out using the wear test device which was designed for this study in air, $10^-2$ Torr and $10^-4$ Torr. The friction coefficient depends entirely on atmospheric pressure and alumina with lower purity than higher purity has been much affected by heat accumulation. The friction surface of ceramics have been protected in the air by the influence of the oxides transferred from STB2. However, the protective layer can not be formed due to the decrease of oxygen in vacuum.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.322-326
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• 2001

Hard disk drive(HDD) consists of a head/slider system which flies over the magnetic disk at an extremely low height. As the density of HDD increases the flying height of the head needs to be decreased. This increases the chance for contact between the slider and the disk. This paper addresses some key issues related to surface failure characteristics of HDD. It is shown that flying behavior of the slider during contact-start-stop cycle can be analyzed based on different regimes of air film lubrication, experimental methods for identifying the underlying mechanisms and improving the reliability of HDD are discussed.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.79-84
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• 2007

Some surface pattern of tribological application is an attractive technology of engineered surface. Therefore, friction reduction is considered to be necessary for improved efficiency of machine. This study investigated the effect of friction property for angles of micro-crosshatch groove surface pattern on bearing steel using pin-on-disk test. We obtain sample which can be fabricated by photolithography process. We discuss the friction property depend on an angle of crosshatch groove surface pattern. We can verify the lubrication mechanism as Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter under the lubrication condition. It was found that the friction coefficient was related to angle of crosshatch groove pattern on contact surface.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.1
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• pp.240-247
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• 2003

The tribological characteristics of FDTS (1H, 1H, 2H, 2H-Perflurodecyltrichlorosilane) SAM (self-assembled monolayer) and OTS (octadecyltrichlorosilane) SAM treated by high temperature annealing have been investigated from the viewpoint of stiction, adhesion and friction in micro/nano scale. From the experimental results, it was found that OTS SAM gets destroyed at 20$0^{\circ}C$ and stiction, adhesion and friction coefficient increased, but FDTS SAM was stable up to 40$0^{\circ}C$. Also, it was found that the friction coefficient of normal OTS SAM below 20$0^{\circ}C$ is lower than that of FDTS SAM in micro/nano scale, but stiction and adhesion is vice versa. This work shows the importance of surface group of self-assembled monolayer in dictating the tribological characteristics and thermal stability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.622-625
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• 2004

The CMP monitoring system was newly developed by the aid of friction force measurement, resulting from installation of piezoelectric quartz sensor on R&D polisher. The correlation between friction and CMP results was investigated in terms of tribological aspects by using the monitoring system. Various friction signals were monitored and analyzed by the change of experimental conditions such as pressure, velocity, pad and slurry. First of all, the lubrication regimes were classified with Sommerfeld Number through measuring coefficient of friction in ILD CMP. And then, the removal mechanism of abrasives could be understood through the correlation with removal rate and coefficient of friction. Especially, the amount of material removal per unit sliding distance is directly proportional to the friction force. The uniformity of CMP performances was also deteriorated as coefficient of friction increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.211-214
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• 2003

The tribological properties of amphiphilic monolayers and composite multilayer on silicon surface were investigated using micro-tribometer and Auger Electron Spectroscopy. Langmuir-Blodgett (LB) monolayers from behenic acid. 2.4-heneicosanedione(HD) and its copper complex((HD)$_2$Cu) were fabricated on silicon surface and the composite multilayer of 5-bilayer of (HD)$_2$Cu was fabricated on the surface of octadecyltrichlorsilane (OTS) self-assembled monolayer(SAM). We observed that LB monolayers and the composite multilayer exhibited a steady and excellent friction response when compared with the OTS SAM. These LB mono and multilayer also showed much higher wear-resistance than the OTS SAM.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.393-397
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• 2003

Recently, rotating elements which use mechanical and electrical systems have been utilized for high speed and accuracy to increase the performance. The most important thing to get a more reliable system is to understand the friction, wear and characteristics which has an effect on various coated surfaces. In this study, the tribologicali characteristics of various soft/hard materials were investigated by using a custom-built pin-on-reciprocator tester From the experimental results, it was found that the friction coefficients of the soft material coated surfaces were lower under various normal loads due to trier self-lubricating ability and material transfer to the counter surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1589-1595
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• 2000

레이저 텍스쳐와 미케니칼 텍스쳐 컴퓨터 하드디스크의 마찰과 마코 매카니즘이 Contact Start/Stop test 실행후의 특성들에 대해 연구되었다. 다양한 분석적이고 기계적인 테스트 기술들이 이용되었다. 형상, 조도, 화학적 조성, 기계적 성질, CSS 로부터 기인된 코팅의 마찰특성들에 대해 그 변화들을 조사하였다. 즉, AFM(Atomic Force Microscopy), Nano-Indentation, Nano-Scratch, TOF-SIMS(Time of Flight Secondary Ion Mass Spectroscopy), AES(Auger Electronic Spectroscopy)등이 이 연구에 적용되었다. 레이저 텍스쳐 범프의 표면조도와 미케니칼 텍스쳐 지역의 표면조도는 각각 대략적으로 4nm 와 7nm 감소되었다. 탄성계수와 경도값은 CSS test후에 증가하였고 가장 바깥쪽의 코팅층의 변형강화가 생겨났다. 자성층과 Ni-P 층 사이에 점착성의 문제가 확인되었다. TOF-SIMS 분석은 C 와 $C_2F_5$의 세기에 있어서 감소를 드러냈고 이것은 코팅 표면에 윤활제 요소의 마모를 확실시 할수 있는 결과로 나타났다.