• Composites Research
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• 제36권3호
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• pp.141-153
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• 2023

본 리뷰 논문에서는 일반 접촉 역학 이론과 더불어 유기탄성체 마찰에 관한 이론 및 배경을 소개한다. 특히 Greenwood & Williamson 접촉 역학 이론을 확장하여 거친 표면을 자기-아핀(self-affine) 특성으로 고려한 접촉 역학 및 마찰의 수학적 모델을 제시한 Klüppel & Heinrich 이론을 중심으로 유기탄성체 복합재료의 마찰 거동에 대해 살펴본다. 자기-아핀 특성에 의한 노면의 멀티스케일 거칠기로 인해 미끄러짐 마찰 시 유기탄성체 복합재료는 다양한 주파수에 따른 동적 변형이 가해지며 이때 재료가 나타내는 점탄성이 마찰 거동에 주요한 영향을 미친다. 따라서 유기탄성체 복합재료의 비선형 점탄성을 고려하여 광범위한 주파수 영역에서의 점탄성 거동인 마스터커브를 구축하는 원리 및 방법을 제시하였다. 마지막으로 유기탄성체 복합재료 마찰 이론을 타이어 트레드 컴파운드와 노면 간의 마찰에 응용한 실험적 결과와 그 물리적 의미를 이론과 접목하여 설명하였다.

• 한국세라믹학회지
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• 제40권6호
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• pp.525-529
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• 2003

Biotribological properties, such as wear rate and friction coefficient, of 3Y-TZP and Low Temperature Degradation (LTD) free materials were investigated via a ball(SiC)-on-plate sliding wear test to evaluate the relationship between wear mechanism and phase transformation. Wear test was conducted with a sliding speed of 0.035 m/s at room temperature and at 25$0^{\circ}C$ in air under a normal load of 49 N, respectively. Although friction coefficient of 3Y-TZP was the lowest due to the fine grain size, the highest wear loss and rate were observed due to the debris of monoclinic grains introduced during sliding and their values increased drastically with raising temperature. However, the biotribological properties of LTD-free materials were insensitive to temperature due to the inertness of the phase transformation, suggesting that they may be applicable to the biomechanical parts.

• KSTLE International Journal
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• 제10권1_2호
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• pp.1-5
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• 2009

This paper reports an investigation on nanotribological properties of silicon nanochannels coated by a diamond-like carbon (DLC) film. The nanochannels were fabricated on Si (100) wafers by using photolithography and reactive ion etching (RIE) techniques. The channeled surfaces (Si channels) were then further modified by coating thin DLC film. Water contact angle of the modified and unmodified Si surfaces was examined by an anglemeter using the sessile-drop method. Nanotribological properties, namely friction and adhesion forces, of the Si channels coated with DLC (DLC-coated Si channels) were investigated in comparison with those of the flat Si, DLC-coated flat Si (flat DLC), and Si channels, using an atomic force microscope (AFM). Results showed that the DLC-coated Si channels greatly increased hydrophobicity of silicon surfaces. The DLC coating and Si channels themselves individually reduced adhesion and friction forces of the flat Si. Further, the DLC-coated Si channels exhibited the lowest values of these forces, owing to the combined effect of reduced contact area through the channeling and low surface energy of the DLC. This combined modification could prove a promising method for tribological applications at small scales.

• 한국재료학회지
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• 제17권11호
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• pp.601-605
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• 2007

The tribological properties of acrylonitrile-butadiene rubber (NBR) filled with two kinds of carbon black filler were examined. Different types of Semi-Reinforcing Furnace (SRF), and High Abrasion Furnace (HAF) blacks were used as filler material to test the influence of carbon black particle size on the friction and wear of NBR. Results from tribological tests using a ball on disk method showed that the smaller HAF particles were more effective for reducing the wear of NBR during frictional sliding. The hardness, elastic modulus at 100% elongation, and elongation at break were measured to examine the correlation between the effects of carbon black on the mechanical and tribological properties of the NBR specimens. The wear tracks of the NBR specimens were observed with scanning electron microscopy (SEM). The wear tracks for NBR with different ratios of SRF and HAF showed clearly different abrasion patterns. Mechanisms for the friction and wear behavior of NBR with different sizes of carbon black filler were proposed using evidence from wear track observation, as well as the mechanical and tribological test results.

• 한국의류학회지
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• 제28권1호
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• pp.112-118
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• 2004

Recently, as the percentage of women employment has been growing, the demand for various facilities and services regarding household duties and infant rearing is increasing and so do the amount of the disposable diaper used. Among the components of disposable diaper, the top sheet contacting with infant skin directly is usually made with nonwoven textiles. Therefore, the mechanical and surface characteristics of the nonwovens used in disposable diaper are important for the skin health of infants. In this study, we have explored the mechanical and surface properties, such as friction coefficient, fluid permeability and strength, of the nonwovens used for disposable diaper top sheet and observed the variation of their properties with abrasion cycles. Nonwoven materials examined in this study are 100% cotton spunlace, 100% tencel spunlace, 100% polypropylene (PP) thermal bonding and 100% PP air through (Thru-air bonded carded web). From the result of KES-F analysis, we've found that 100% PP air through type nonwoven had a low friction coefficient and showed a little change in surface properties as increasing abrasion cycles. Moreover, it revealed superior fluid permeability and quick-drying character. On the other hand, though showing an excellent absorption force, the spun lace type nonwoven made of 100% cotton and 100% tencel displayed relatively low abrasion strength especially in wetting condition.

• 한국의류학회지
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• 제28권8호
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• pp.1153-1164
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• 2004

The purpose of this study was to knitted nine kinds of single knit and examined mechanical properties and hand to provide the fact that knit, tuck and miss stitch applied to various structure have an effect on hand of weft knitted fabrics. It was good to use tuck stitch rather than miss stitch to increase elasticity of knitted fabrics. As tuck stitch and miss stitch were double or triple overlaps, tensile resilence(RT) decreased by increase of friction contacted among stitch. As cross tuck stitch and cross miss stitch were knitted double or triple, bending rigidity(B), hysteresis of bending moment(2HB) and shearing(G) properties increased by jamming of stitch. As tuck stitch and miss stitch were overlap, thickness increased and they became thicker than miss stitch. Also, as they became thicker by these tuck stitch and miss stitch, compressional energy(WC) increased. It appeared that coefficient of friction(MIU) of cross tuck stitch was larger than coefficient of cross miss stitch. Mean deviation of surface roughness(SMD) had a tendency to be larger as tuck stitch and miss stitch increased. As cross tuck stitch and cross miss stitch were overlaps double or triple, KOSHI and FUKURAMI increased, total hand value(TIV) and NUMERI appeared high in double cross tuck stitch and double cross miss stitch.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.40-43
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• 2018

Various Ni-doped carbon (C : Ni) thin films were fabricated using different Ni target power densities by unbalanced magnetron sputtering (UBM). The effects of target power density on the structural, physical, surface, and electrical properties of C : Ni films were investigated. The UBM C : Ni thin films exhibited uniformly smooth surfaces. The rms surface roughness and friction coefficient values of the C : Ni films decreased with the increase in target power density. The physical properties of the films such as hardness and elastic moduli increased while their electrical properties such as resistivity decreased with the increase in the target power density. These results show that an increase of the power density leads to an increase in the proportion of Ni and nanocrystallization of the amorphous carbon film; this contributes to the changes observed in the physical and electrical characteristics.

• Design & Manufacturing
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• 제15권3호
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• pp.7-12
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• 2021

Plastic injection molds used for rapid heating and cooling must minimize surface damage due to friction and maintain excellent thermal and low electrical conductivity. Accordingly, various surface treatments are being applied. The properties of Al₂O₃ coating and DLC coating were compared to find the optimal surface treatment method. Al₂O₃ coating was deposited by thermal spray method. DLC films were deposited by sputtering process in room temperature and high temperature PECVD (Plasma enhanced chemical vapor deposition) process in 723 K temperature. For the evaluation of physical properties, the electrical and thermal conductivity including surface hardness, adhesion and wear resistance were analyzed. The electrical resistance of the all coated samples was showed insulation properties of 24 MΩ/sq or more. Especially, the friction coefficient of high temp. DLC coating was the lowest at 0.134.

• 한국지반환경공학회 논문집
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• 제18권2호
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• pp.29-37
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• 2017

집중호우로 인하여 산악지반에 발생하는 토석류의 거동은 대상지반 세립분의 전단강도 및 유변학적 특성들에 의하여 영향을 받기 때문에, 두 특성에 대한 정수는 토석류 거동을 파악하는데 매우 중요한 요소이다. 본 연구에서는 직접전단 실험을 통하여 세립분의 전단강도 및 유변학적 정수를 평가하고자 하였다. 건조상태와 액성한계상태로 조성된 두 가지 세립분 시료에 대하여 직접 전단실험을 수행하였으며, 연직응력에 따른 전단강도를 측정하여 점착력과 내부마찰각을 산정하였다. 또한 액성한계로 조성된 시료의 잔류전단강도를 획득하기 위하여 전단변형률속도와 전단방향을 변화시켜 반복전단실험을 수행하였다. 실험 결과, 액성한계상태의 시료는 건조 상태 시료에 비해 내부마찰각은 작지만 점착력은 더 큰 것으로 나타났으며, 잔류전단강도를 통해 산정한 내부마찰각과 점착력은 첨두전단강도에 의해 산정된 결과보다 작은 것으로 나타났다. 반복전단 결과, 전단변형률속도와 잔류전단강도는 선형적인 관계를 보였으며, 전단변형률속도-잔류전단강도 관계의 기울기로써 결정되는 점성은 약 $73.60Pa{\cdot}s$로 산정되었다. 본 연구는 직접전단 장비가 산악지반 토석류 거동과 관련된 세립분의 전단강도 및 유변학적 정수 산정에 효과적으로 활용될 수 있음을 보여준다.

• 한국건축시공학회지
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• 제14권2호
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• pp.118-126
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• 2014

본 연구에서는 콘크리트를 펌프압송할 경우, 콘크리트의 배합조건에 따른 레올로지 특성의 차이와 압송속도에 의해 펌핑관내의 마찰저항력이 달라지게 되는 것에 착안하여 레올로지특성과 펌핑관내 마찰저항계수의 상관관계를 도출하고자 하였다. 이를 위해 콘크리트용 레올로지 측정장치와 관내마찰저항 평가시험장치를 이용하여 레올로지특성과 마찰저항력을 측정하기 위한 펌프압송실험을 수행하였다. 연구결과, 펌핑전후의 레올로지특성에 큰 변화가 있는 것으로 파악되었으며, 시험장치에 의해 측정된 관내마찰 저항력과 이론상의 관내 최대전단력이 거의 동일한 값을 나타냈다. 또한, 펌핑 후 콘크리트의 소성점도와 관내마찰저항계수의 상관관계가 매우 높은 것으로 나타났으며, 본 연구에서 도출된 마찰저항계수에 의한 압송압력의 예측값이 실측결과와 매우 높은 상관관계를 갖는 것으로 나타났다.