• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1996년도 제24회 춘계학술대회
• /
• pp.25-29
• /
• 1996

The fretting wear characteristics for Zircaloy-4 tube used as fuel rod in the nuclear power plant have been investigated. The fretting wear tester was designed and manufactured for this experiment. This study was focused on main factors of fretting wear, cycle, slip amplitude and normal load. The worn surfaces were observed by SEM.

• 한국정밀공학회지
• /
• 제28권9호
• /
• pp.1062-1069
• /
• 2011

In electro-galvanizing line to manufacture the electro-galvanized steel sheet, polishing system is required to maintain clean surface of conductor roll and to secure the quality of the steel sheet. At the same time, prediction and decision of the replacement cycle for felt material and its brush installed in the polishing system is also important because the brush is directly contacted on the conductor roll surface. In this study, the polishing system has been designed which the brush is repetitive translating according to the longitudinal direction of the conductor roll. Furthermore, the prediction on the wear-life of the felt material used for the brush is performed using the contact pressure extracted by finite element analysis. And to verify the predicted wear-life of the felt material, the experimental study is also carried out. From the comparison result between the predicted and the measured wear-life of the felt material, it is presented that the wear-life and the replacement cycle of the felt material are well predicted by considering a wear compensation factor, and the wear compensation factor is useful and reasonable.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 춘계학술대회
• /
• pp.252-254
• /
• 2017

자동차 타이어는 차량을 운행하는데 있어 중요한 요소 중 하나이다. 타이어가 마모됨에 따라 자동차 제동거리가 늘어나고 슬립현상이 발생할 가능성이 크다. 따라서 주기적으로 타이어의 마모도를 확인하고 교체해주어야 한다. 기존에는 사람이 직접 마모도를 확인하여 타이어 교체여부를 판단하였다. 하지만 사람에 따라 기준이 다르기 때문에 교체 주기가 불분명해진다. 본 논문에서는 모터 회전각도를 활용한 타이어 마모도 확인 기법을 통해 명확한 교체주기를 마련한다. 명확한 교체주기가 정립됨으로써 타이어로 인한 차량 사고율이 줄어들 것으로 기대되기 때문에 모터 회전 각도를 활용한 타이어 마모도 확인 기법을 제안한다.

• 한국자동차공학회논문집
• /
• 제15권4호
• /
• pp.101-107
• /
• 2007

This study investigated the wear of the valve and seat insert seating faces. A tester, an exhaust valve and a seat insert were used. Test variables were cycle numbers ($2{\times}10^6,\;4{\times}10^6,\;6{\times}10^6\;and\;8{\times}10^6$) and Hz (10Hz and 25Hz). The other test conditions such as temperature ($350^{\circ}C$), fuel (LPG) and load (1960N) were fixed. The 10Hz tests indicated that the average Rmax of the valve increased at the rate of $7.76{\mu}m/10^6$ cycles starting from $29.42{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $8.57{\mu}m/10^6$ cycles starting from $34.19{\mu}m$ at the $2{\times}10^6$ cycles. The 25Hz tests indicated that the average Rmax of the valve increased at the rate of $1.58{\mu}m/10^6$ cycles starting from $74.2{\mu}m$ at the $2{\times}10^6$ cycles and that of the seat insert increased at the rate of $1.25{\mu}m/10^6$ cycles starting from $83.95{\mu}m$ at the $2{\times}10^6$ cycles. The tribochemical reaction product covered the two seating faces, preventing the wear of the seating faces. As cycle numbers became greater, the average Rmax of the seating faces became greater, but the increase rate varied significantly depending on the Hz. The wear mechanism of the two faces was investigated through the tribochemical reaction.

• Tribology and Lubricants
• /
• 제35권1호
• /
• pp.30-36
• /
• 2019

The tribological properties of paper-based friction materials are crucial to the performance of a wet clutch system. In this work, the friction and wear characteristics of a paper-based friction material in boundary lubrication state was experimentally investigated using a pin-on-reciprocating tribotester under various normal forces and temperatures. It was found that the wear rate of the friction material increased from $5.8{\times}10^{-6}mm^3/N/cycle$ to $5.5{\times}10^{-5}mm^3/N/cycle$ after 1,700 cycles of testing at $80^{\circ}C$ as normal force increased from 2 N to 7 N. The friction coefficient was also found to increase from 0.135 to 0.155 with increasing normal force from 2 N to 7 N. The increase in contact pressure with increasing normal force may be responsible for these results. In addition, as temperature increased from $20^{\circ}C$ to $80^{\circ}C$, the wear rate of the friction materials increased from $2.0{\times}10^{-5}mm^3/N/cycle$ to $3.6{\times}10^{-5}mm^3/N/cycle$ while the friction coefficient decreased from 0.163 to 0.146. This result may be associated with the decrease in the hardness of friction materials with increasing temperature. Furthermore, plastic deformation on the friction materials was mainly observed after the test. The outcome of this work may be useful to gain a better understanding of the tribological properties of friction materials, and therefore can contribute to the development of friction materials with enhanced performance for wet clutch systems.

• 치위생과학회지
• /
• 제13권2호
• /
• pp.151-157
• /
• 2013

본 연구는 어린이집에서 유아들이 사용하고 있는 칫솔의 칫솔마모 상태를 평가하여, 유아의 칫솔 교체시기에 대한 적절한 기준을 확립하는 데 도움을 주고자 2012년 9월 20일부터 11월 6일까지 1,022개의 칫솔을 수거한 뒤 칫솔마모도 및 마모율을 평가하여 다음과 같은 결과를 얻었다. 1. 칫솔마모도 측정 결과, 조사 대상 칫솔 중 48.5%가 0.400 이상의 마모도를 보였고, 평균 마모도는 $0.421{\pm}0.239$로 조사되어, 전체적으로 높은 칫솔마모도를 보였다. 2. 칫솔마모율 측정 결과, 마모율 2점과 3점이 차지하는 비율이 70.4%였으며, 평균 마모율은 $1.936{\pm}0.848$로 나타나 전체적으로 높은 칫솔마모율을 보였다. 3. 칫솔관리 실태에 대한 조사 결과, 평균 칫솔 교환주기는 5~8주가 63.9%로 가장 많았고, 칫솔 교환방법은 칫솔모의 마모 상태에 따라 교체한다는 응답이 52.7%로 조사되었다. 이상의 결과를 바탕으로, 유아들의 칫솔에 대한 관리가 적절히 이루어질 수 있도록 보육을 담당하는 교사 및 보호자에 대한 지도가 필요할 것이며, 유아의 올바른 칫솔 교체주기에 대한 명확한 기준 확립과 효율적인 구강보건교육 방안도 마련되어야 할 것이다.

• Nuclear Engineering and Technology
• /
• 제37권2호
• /
• pp.201-206
• /
• 2005

Fretting, which is a special type of wear, is defined as small amplitude relative motion along the contacting interface between two materials. The structural integrity of steam generators in nuclear power plants is very much dependent upon the fretting wear characteristics of Inconel 690 U-tubes. In this study, a finite element model that can simulate fretting wear on the secondary side of the steam generator was developed and used for a quantitative investigation of the fretting wear phenomenon. Finite element modeling of elastic contact wear problems was performed to demonstrate the feasibility of applying the finite element method to fretting wear problems. The elastic beam problem, with existing solutions, is treated as a numerical example. By introducing a control parameter s, which scaled up the wear constant and scaled down the cycle numbers, the algorithm was shown to greatly reduce the time required for the analysis. The work rate model was adopted in the wear model. In the three-dimensional finite element analysis, a quarterly symmetric model was used to simulate cross tubes contacting at right angles. The wear constant of Inconel 690 in the work rate model was taken as $K=26.7{\times}10^{-15}\;Pa^{-1}$ from experimental data obtained using a fretting wear test rig with a piezoelectric actuator. The analyses revealed donut-shaped wear along the contacting boundary, which is a typical feature of fretting wear.

• Tribology and Lubricants
• /
• 제13권3호
• /
• pp.28-32
• /
• 1997

Indentation, scratch and sliding tests were carried out in this paper to predict the critical loads and the failure modes of TiN-coated specimen. The test specimens were S20C steels with three different substrate hardness, roughness and coating thickness. The scratch test shows that the coating thickness has more dominant effect on the critical load of coated disk than the hardness and the roughness. Using the percent contact load, the ratio of sliding load to the critical scratch load, the cycles to failure are measured to predict the wear-life of TiN film. On the wear-life diagram the percent loads and the cycle to failure show the good linear relation on semi-log coordinate. With decreasing loads, the diagram shows the wear-limit at which the coated disk survives more than 4000 cycles.

• 한국의상디자인학회지
• /
• 제6권2호
• /
• pp.89-102
• /
• 2004

Modern society is age of sports just as health and leisure became dominant concern, which has caused the fixation and development to sports wear considered as fashion for everyday dress. This paper focused on the development process and aesthetic characteristics of knit design expressed in the 20th century sports wear. The importance and direction of knit design in modern sports wear is expected. Style, items, fabrics, colors, details and top designers were analyzed in sports wear from the 1910' s to 1990' s. Sports wear can be categorized into two of the active sports wear and spectator sports wear. Since disappearance of division between ordinary wear and sports fashion in the 1970' s, the functional wear of leggings, cycle shorts, exercise clothes, leotard, and leg warmer appeared. Vicennial developments of synthetic fibers and new fabrics have caused the great changes in knit design. Colors were vivid in the 1950' s, metallic in the 1970' s and neon in the 1990' s. Sportive sense was expressed by various details. The dominant knit designers who expressed aesthetic characteristics to sports wear were Coco Chanel, Claire McCardell, Balenciaga, Andre Courrege, Pierre Cardin, Yves Saint-Laurent, Ralph Lauren, Donna Karan, and Giogio Armani.

• Tribology and Lubricants
• /
• 제36권4호
• /
• pp.232-243
• /
• 2020

It is essential to predict the amount of wear and surface parameters for a surface where relative motion occurs. In the asperity-based model for wear prediction, only the average contact pressure can be obtained. Hence, the accuracy of wear analysis is poor. In this study, DC-FFT is used to obtain the pressure of each node, and wear analysis is performed by considering the effect of the pressure gradient. The numerical surface generation method is used to create Gaussian, negatively skewed, and positively skewed surfaces for wear analysis. The spatial and height distributions of each surface are analyzed to confirm the effectiveness of the generated surface. Furthermore, wear analysis is performed using DC-FFT and Archard's wear formula. After analysis, it is confirmed that all peaks are removed and only valleys remain on the surface. The RMS roughness and Sk continue to decrease and Ku increases as the cycle progresses. It is observed that the surface parameters are significantly affected by the radius of curvature of the asperity. This analysis method is more accurate than the existing average wear and truncation models because the change in asperity shape during the wear process is reflected in detail.