• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04b
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• pp.25-29
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• 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.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1062-1069
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• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.252-254
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• 2017

Tire is one of the most important to drive cars. There is high possibility to occur slip phenomenon and to increase braking distance depending on tire wear. Therefore, you should be check tire wear and replace tires periodically. In the past, most people manually check the wear level and judged whether or not to replace the tire. But, since the standard is different for each person, the replacement cycle becomes unclear. Since a clear replacement cycle is established, it is expected that the accident rate of a vehicle caused by a tire will be reduced. Therefore, i propose detection method for a tire wear using a motor rotation angle.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.101-107
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• 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
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• v.35 no.1
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• pp.30-36
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• 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.

• Journal of dental hygiene science
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• v.13 no.2
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• pp.151-157
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• 2013

The purpose of this study was to examine the toothbrush bristles' wear index and wear rate used by preschool children to provide information on the establishment of criteria for toothbrush replacement cycle for preschool children. One thousand twenty-two toothbrushes were collected from September 20 to November 16, 2012 was analyzed. The findings of the study were as follows: 1. As a result of analyzing the toothbrush wear index, 48.5% of the collected toothbrushes was above 0.400, and the average wear index was $0.421{\pm}0.239$. 2. As a result of analyzing the wear rate of the toothbrushes, score 2 and 3 accounted for 70.4%, and the average wear rate stood at $1.936{\pm}0.848$. 3. As a result of analyzing the state of toothbrush management, the most common average toothbrush replacement cycle was one or two months (63.9%). Concerning the method of toothbrush replacement, the largest group (52.7%) replied they changed toothbrushes based on the abrasivity of toothbrush bristles, and 16.7 percent did that at the request of parents. Given the above-mentioned findings of the study, preschool teachers and parents should be educated to ensure the successful management of preschool children toothbrushes. In addition, it's required to set evident criteria for the right toothbrush replacement cycle for preschool children, and how to provide oral health education in an efficient way should be considered as well.

• Nuclear Engineering and Technology
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• v.37 no.2
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• pp.201-206
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• 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
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• v.13 no.3
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• pp.28-32
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• 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.

• Journal of the Korea Fashion and Costume Design Association
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• v.6 no.2
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• pp.89-102
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• 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
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• v.36 no.4
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• pp.232-243
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• 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.