• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.778-783
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• 1999

The effect of carbon fiber orientation on the tribological properties of carbon fiber/epoxy composites used as a reflecting material for the electromagnetic wave has been investigated. It was found that the carbon fiber/epoxy composite which slides normal to prepreg lay-up direction had less friction and wear that those slides parallel to prepreg fiber lay-up direction due to the increase of delamination between carbon fiber and epoxy. Composite with unidirectional orientation($0/0^{\circ}$) had higher tribological properties than those with multidirectional orientation($0/45/90/-45^{\circ}$ and $0/90^{\circ}$) when the sliding direction was normal to prepreg lay-up direction. This was caused by the debonding between carbon fiber and epoxy which is proportional to contact area between the sliding surface and carbon fiber. Opposite results have been found when the sliding direction was parallel to prepreg lay-up direction due tot he tensile force applied on carbon fiber. In addition, it was shown that wear factor increased with increasing sliding velocity but the friction coefficient did not depend upon the sliding velocity.

• Science of Emotion and Sensibility
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• v.9 no.2
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• pp.133-140
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• 2006

In order to investigate the sensation of the fabric sound simulating the real wear-condition, the fabric sound simulator using reciprocating friction was developed. Fabric sounds from 5 specimen were generated by the fabric sound simulator and recorded using high performance microphone. Physical sound parameters of fabrics including level pressure of total sound (LPT), level range (${\Delta}L$), and frequency differences (${\Delta}f$) were calculated. For psychological evaluation, seven adjectives for sound (softness, loudness, sharpness, clearness, roughness, highness, and pleasantness) were used as the semantic differential scale. Fabric sounds by reciprocating friction of nylon taffeta and polyester leno had the highest value of LPT and evaluated as loud, sharp, rough, and unpleasant while polyester ultra suede and silk crepe de chine haying the lower LPT and ${\Delta}f$ were perceived as soft and quite. Comparing with fabric sound by one-way friction, fabric sound by reciprocation friction was perceived as more sharp, loud, and rough. LPT was also the most important factor affecting the sensation of the fabric sound by reciprocating friction.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.337-343
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• 2004

This paper presents an experimental study of friction and wear properties of a unidirectional oriented continuous crbon-fiber reinforced epoxy composite at the ambient temperature. Friction and wear experiments were conducted in the three principal sliding direction of the fiber orientation in the composite were selected against the stainless steel counterpart specularly processed were using a pin -on-disc apparatus. Friction coefficient and specific wear rate at various normal loads and sliding velocities wear determined. When sliding took place against smooth and hard counterpart, the hightest were resistance and the lowest friction coefficient were observed in the anti-parallel direction. The wear track of the worn specimens was examined with a scanning electron microscope(SEM) to observe the damaged fibers on the surface. In addition, SEM observations of the worn surfaces allowed to identify the involved different wear mechanisms.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.178-181
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• 2011

본 연구에서는 광섬유센서를 내장한 스마트강연선을 이용하여 초고성능콘트리트로 제작된 하이브리드 사장교 세그먼트의 횡방향 도입 긴장력을 계측하고 세그먼트 내부의 프리스트레스를 계측하여 즉시손실에 해당하는 정착장치 활동에 의한 손실과 마찰손실을 도로교설계기준(2005)의 설계 마찰손실과 비교하였다. 제작된 2개의 UHPC 사장교 세그먼트는 횡방향 길이 16.7m, 종방향 길이 1.75m, 높이 1.5m이며 각 시험체의 1/4, 1/2, 3/4지점에 긴장력을 계측하기 위해 3개의 FBG센서를 배치하였다. 긴장력은 유압잭을 이용하여 5개의 강연선에 동시에 순차적으로 도입되었으며, 단부에서 최대 도입 긴장력은 세그먼트 1은 734kN, 세그먼트 2는 639kN이었다. 도로교설계기준에 제시된 마찰계수의 중간값(파상마찰계수=0.00405, 곡률마찰계수=0.20)을 사용하여 FBG센서 위치에서 계산된 긴장력은 계측치와 5% 이내의 차이를 보였으며, 정착장치 활동에 의한 순간손실은 긴장단에서 최대 12.8%로 계측되었다. 이로부터 이 연구에서 제시하는 긴장력계측방법의 적용성을 입증할 수 있었으며, 향후 이 방법은 프리스트레스트 콘크리트 교량의 설계기준 마찰계수 개정을 위한 연구에 좋은 도구로 활용될 수 있을 것으로 기대된다.

• Composites Research
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• v.23 no.2
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• pp.10-16
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• 2010

$Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) were manufactured by squeeze casting method investigated for their tribological properties. The pin specimens had different ratios of fiber to particle content but their total weight fraction was constant at 20 wt. %. Tribological tests were performed with a pin-on-disk friction and wear tester. The investigation of the dry tribological characteristics of hybrid MMCs were carried out at room temperature and elevated temperature of$100^{\circ}C$ and$150^{\circ}C$. The morphologies of worn surfaces were examined by scanning electron microscope (SEM) to observe tribological characteristics and investigate wear behavior. The results revealed that the wear resistance improved with the content of SiCp increased of the planar random (PR) MMCs at room temperature. At the elevated temperature, it revealed that the wear resistance of normal (N) MMCs was superior to that of the PR-MMCs due to PR-fibers were easily pulled out holistically from the worn surface. Meanwhile, the coefficient of friction decreased with the temperature increasing.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.344-350
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• 2004

This is the study on dry sliding wear behavior of unidirectional carbon fiber reinforced epoxy matrix composite at ambient temperature. The wear rates and friction coefficients against the stainless steel counterpart specularly processed were experimentally determined and the resulting wear mechanisms were microscopically observed. Three principal sliding directions relative to the dominant fiber orientation in the composite wear selected. When sliding took place against smooth and hard counterpart, the highest were resistance and the lowest friction coefficient were observed in the antiparallel direction. When the velocity between the composite and the counterpart went up, the wear rate increased. The fiber destruction and cracking caused fiber bending on the contact surface, which was discovered to be dominant wear mechanism.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.88-88
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• 2004

내압을 받는 압력관의 파괴는 원주방향의 응력이 주된 요인이므로, 압력관의 안전성을 평가를 위해서는 원주방향의 인장특성을 아는 것이 필요하다. 소형 압력관의 인장특성을 평가할 때, 정확한 원주방향의 인장특성을 알기 위해서는 관으로 가공된 후의 재료로 시험해야 하지만, 부피의 제약으로 인하여 원주방향으로의 표준 인장시험편을 제작하지 못하므로 가공하기 전의 재료의 물성치를 사용하고 있다. 이를 개선하고자 원주방향의 인장특성을 평가하기 위한 방법의 하나로 링 시험법(ring test)이 있다.(중략)

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.114-117
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• 1998

양모의 수축은 양모를 습윤 처리할 때 양모 스케일의 모근과 모단방향의 마찰계수가 다르기 때문에 일어나는 현상이므로 양모의 스케일을 화학적으로 개질하여 두 방향의 마찰계수의 차를 감소시키면 양모의 수축을 감소시킬 수 있다. 이와 같은 원리로 방축효과를 주는 양모의 방축 가공제로는 90% 이상이 염소 또는 염소를 발하는 물질인데 이 가공으로 인한 폐수는 환경문제를 일으키는AOX를 함유하고 있어서 이를 대체하고자 하는 연구가 여러 곳에서 진행되고 있다. (중략)

• Geotechnical Engineering
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• v.11 no.4
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• pp.99-110
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• 1995

In this study, friction angles on the surface of vertical rigid ground anchor in normally consolidated dry sand were measured by model pullout tests in laboratory. Friction angles were obtained from the normal and shear stresses measured along depth of the anchor stir face by attaching several 2-dimensional load cells. Model tests were conducted under the plane strain state and axial symmetric state. From the results of tests, it was concluded that the maximum friction angle on the anchor surface coincides nearly with the maximum angle of stress obliquity on the plane of zero-extension direction obtained by plane strain compression test. This result was made with regard to the strength anisotropy and stress dependency of sand. It showed that when angle of shear resistance of the sand is applied to the friction angle of the anchor surface, the design capacity could be less than the applied force, thus making the anchor unsafe.

• Journal of Korean Society of Steel Construction
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• v.10 no.1 s.34
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• pp.101-113
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• 1998

In this study, we research the influence of butt-welded joints in high tension bolted joints on the static and fatigue strength. As a results, if it's located inside or outside of the friction surface, the fatigue strength decrease, and the decrease of fatigue strength is greater in cases that the butt-welded joints exist outside of the friction surface. But the influence of butt-welded joint on the fatigue strength satisfies category B of the Specifications.