• Title/Summary/Keyword: 마찰측정

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A Study on Characteristics of the Unit Skin Friction Using the Wall Roughness in the Soft Rock (연암부 벽면거칠기를 이용한 단위주면마찰력 특성에 관한 연구)

  • Hong, Seok-Woo;Hwang, Geun-Bae
    • Journal of the Korean Geotechnical Society
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    • v.35 no.12
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    • pp.7-13
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    • 2019
  • In the case of the drilled shaft, one of the methods for calculating unit skin friction stress of rock socket parts is to measure the roughness of the excavated face. This method is to estimate the unit skin frictional resistance using a device which measures the roughness shape of the excavated face in the excavation step. In this study, the roughness shapes of the face of the rock socket part in the drilled shaft were measured directly in the perforated hole and the results are used to identify the characteristics of the unit skin friction of the bedrock. In addition, the static load test and the load transfer test were performed on the same pile to verify the result of the roughness test.

A study on Sliding Friction and Wear Characteristics of Hybrid Composites at Medium Sliding Speed (중속에서의 하이브리드 복합재료의 미끄럼 마찰 및 마모 특성에 관한 연구)

  • 정형범;윤재륜
    • Composites Research
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    • v.13 no.1
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    • pp.78-88
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    • 2000
  • Tribological properties of fiber composite materials were measured and wear resistant hybrid structure was proposed based upon the understanding of tribological behavior of the composite materials. Unidirectional composites with glass fibers, carbon fibers, and aramid fibers were tested for tribological properties in order to propose a wear resistant hybrid structure. Hybrid composites which contain carbon and aramid fibers were prepared, the specimens were sliced by a water-jet cutter, and friction and wear properties were measured. An experimental set-up was designed and built for the friction and wear test of the composite specimens. Unidirectional fiber composite and hybrid composite specimens were tested to evaluated the tribological behavior for biomimetic applications. It is observed that the friction and wear behavior of fiber composites depends upon fiber orientation, sliding speed, and type of reinforcing fibers.

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The estimation of the wall friction coefficient in tunnels by in-situ measurement (현장측정을 통한 터널 내 벽면마찰계수 추정 연구)

  • Kim, Hyo-Gyu;Choi, Pan-Gyu;Lee, Ho-Hyung;Baek, Doo-San;Na, Kwang-Hoon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.405-421
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    • 2018
  • In most of cases, the wall friction coefficients applied for local tunnel design are quoted directly from foreign data or local design guideline. In the previous studies, the wall friction coefficient was estimated using the velocity decay method. However, it is difficult to estimate the wall friction coefficient when the convergence wind velocity in the tunnel is negative (-) or if there is a change in the natural wind. Therefore, in this study, the wall friction coefficient is estimated by applying the dynamic simulation technique in addition to the conventional the velocity decay method. As a result of the analysis, the coefficient of wall friction in the tunnels for the total of 9 tunnels (18 tubes both directions) was 0.011~0.025, and the mean value was estimated to be 0.020. In addition, the wall friction coefficient obtained quantitatively through this study was compared with the current design criteria.

A Study on the Friction Loss Reduction in Fire Hoses Used at a Fire Scene (화재현장에서 사용하는 소방호스의 마찰손실 감소 방안에 관한 연구)

  • Min, Se-Hong;Kwon, Yong-Joon
    • Fire Science and Engineering
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    • v.27 no.3
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    • pp.52-59
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    • 2013
  • It was described the measured friction loss depending on pressure used and changes in water flow rates for a fire hose used at a fire scene on this study. As a result of actual measurement based on the result obtained by analyzing the use situation of a fire hose such as the kind, quantity, pressure used, etc. of a fire hose, the friction loss in a fire hose under the condition of using by a fire officer at a fire scene was measured as up to 56.8 %. This is much different from the equivalent length of a fire hose used to calculate the pump head in an indoor and outdoor fire-fighting facility. There is no related restrictive regulation on friction loss, there are even no data on friction loss measured by fire hose makers, and spreading a fire hose without considering friction loss at a fire scene can result in an increased length of hose used and a high-pressure water discharge from a fire engine, so this study aims to establish a standard for an equivalent length to friction loss in a fire hose and to propose a spreading method considering friction loss in a fire hose at a fire scene.

Optimization and Application of Si-DLC Coating with Low Friction and High Hardness Property by Using PECVD Method

  • Yeo, Gi-Ho;Mun, Jong-Cheol;Sin, Ui-Cheol;Lee, Hyeon-Seok;Choe, Sun-Ok;Yu, Jae-Mu
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.169.2-169.2
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    • 2013
  • 본 연구에서는 gas를 이용한 PECVD 공법중 이온화 에너지가 높고 대면적 코팅이 용이한 Hybrid 코팅 장비에서 Linear Ion-Gun 이용하여 탄화수소 계열의 gas인 $C_2H_2$ 와 Si을 함유한 TMS (tetramethylsilane, $Si(CH_3)_4)$ gas를 이용하여 저마찰, 고경도 특성을 갖는 Si-DLC 코팅에 대한 연구를 수행하였다. Si-DLC 코팅에 앞서 전처리 공정으로 Linear Ion-Gun에 Ar gas를 주입하고 고전압의 DC 전원을 인가하여 제품 표면의 건식세정 및 표면 활성화를 진행 후, $C_2H_2$ 와 TMS gas를 Linear Ion-Gun에 주입하여 Si-DLC 코팅 공정을 진행하였다. Si-DLC 코팅시 $C_2H_2$ gas 주입량을 고정하고 TMS 가스 유량을 5~20sccm으로 조절하여 Si 함유량에 따른 Si-DLC 코팅막의 특성을 분석하였다. 이렇게 코팅된 Si-DLC의 박막 특성 분석으로 마찰계수 측정을 위해 ball-on-disk 타입의 tribometer를 사용하였으며, 박막 경도 측정은 Nano-indenter를 이용하여 분석을 진행하였다. 그 결과 Si을 포함하지 않는 DLC의 경우 마찰계수가 ~0.2를 가지는 반면, Si-DLC의 경우 Si 함유량이 약 1.5at%일 때, 마찰계수 ~0.04 저마찰의 우수한 특성을 지니며, 박막의 경도는 22[Gpa]로 고경도의 Si-DLC 코팅을 확인할 수 있었다.

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A Study on the Friction Characteristics for Mounting Rubbers on the Automotive Engine (자동차 기관의 마운팅 고무에 대한 마찰특성 연구)

  • Rhee, Bong-Goo;Oh, Seong-Mo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.4
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    • pp.1197-1202
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    • 2010
  • We have studied on the frictional characteristics for mounting rubbers varieties structures on the automotive engine. This paper are using a test apparatus developed in the laboratory, friction and wear characteristics of various rubbers have been analyzed by experimental study. Frictional characteristics has been measured from the normal force and friction force under various operating conditions, such as, loads, speed and temperatures. Therefore, the rubbers are used in a several varieties structures as well as automotive, the relations between the various conditions and frictional characteristics have been investigated.

Evaluation of friction of ceramic brackets in various bracket-wire combinations (브라켓 각도 변화에 따른 세라믹 브라켓의 마찰력 측정)

  • Cha, Jung-Yul;Kim, Kyung-Suk;Kim, Dong-Choon;Hwang, Chung-Ju
    • The korean journal of orthodontics
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    • v.36 no.2 s.115
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    • pp.125-135
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    • 2006
  • The purpose of this study was to measure and compare the level of frictional resistance generated from three currently used ceramic brackets; 1, Crystaline $V^{(R)}$, Tomy International Inc., Tokyo, Japan; 2, $Clarity^{(R)}$, 3M Unitek, Monrovia, CA, USA; 3, $Inspire^{(R)}$, Ormco, Orange, CA, USA; with composite resin brackets, Spirit, Ormco, Orange, CA, USA; and conventional stainless steel brackets, Kosaka, Tomy International Inc., Tokyo, Japan used as controls. In this experiment, the resistance to sliding was studied as a function of four angulations $(0^{\circ},\;5^{\circ},\;10^{\circ}\;and\;15^{\circ})$ using 2 different orthodontic wire alloys: stainless steel (stainless steel, SDS Ormco, Orange, CA, USA), and beta-titanium (TMA, SDS Ormco, Orange, CA, USA). After mounting the 22 mil brackets to the fixture and $.019{\times}.025$ wires ligated with elastic ligatures, the arch wires were slid through the brackets at 5mm/min in the dry state at $34^{\circ}C$. Silica-insert ceramic brackets generated a significantly lower frictional force than did other ceramic brackets, similar to that of stainless steel brackets. Beta-titanium archwires had higher frictional resistance than did stainless steel, and all the brackets showed higher static and kinetic frictional force as the angulation increased. When the angulation exceeded $5^{\circ}$, the active configuration emerged and frictional force quickly increased by 2.5 to 4.5-fold. The order of frictional force of the different wire-bracket couples transposed as the angle increased. The silica-insert ceramic bracket is a valuable alternative to conventional stainless steel brackets for patients with esthetic demands.

Prediction of Pumping Friction Resistance Coefficient in Pipe Influenced by Concrete Rheology Properties (콘크리트의 레올로지 특성에 따른 펌핑관내 마찰저항계수의 예측에 관한 연구)

  • Kim, Hyung-Rae;Cho, Ho-Kyoo;Kim, Jung-Chul;Lee, Kewn-Chu
    • Journal of the Korea Institute of Building Construction
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    • v.14 no.2
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    • pp.118-126
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    • 2014
  • The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for concrete pumping performance for the rapid construction of super-tall buildings. In this study, a quantitative evaluation of concrete fluid characteristics and surface friction resistance was performed, applying different concrete mix proportions and pumping conditions. To achieve this, we developed a temporary horizontal pumping evaluation system to measure pipe pressure and surface friction characteristics, and performed an experiment to investigate the relations between concrete rheology characteristics and friction resistance in pipe. The experiment found that in terms of the rheology characteristics, plastic viscosity was reduced remarkably after pumping. As well, high regression between the surface friction and pressure gradient was confirmed. This means that it is possible to evaluate the friction resistance between concrete and pipe by means of a pumping system that includes a frictional resistance testing pipe. In addition, high regression between the plastic viscosity of concrete after pumping and friction resistance coefficient was confirmed. Finally, it is considered that pumping pressure can be predicted using the friction resistance coefficient derived in this study, and it has high regression.

Developing the Detector Drive System of In-core Flux Mapping System for Nuclear Power Plant (원자력발전소 노내 중성자 분포 측정 설비의 검출기 구동시스템 개발)

  • Cho, Byung-Hak;Shin, Chang-Hoon;Byun, Seung-Hyun
    • Proceedings of the KIEE Conference
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    • 2003.07d
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    • pp.2435-2437
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    • 2003
  • 원자력발전소의 노내 중성자 분포 측정 설비는 고장이 발생하여 기능을 상실하면 발전소를 정지하여야 하는 매우 중요한 설비이다. 국내 가압 경수로형 원전에 사용되고 있는 노내 중성자 분포 측정 방식은 이동식과 고정식으로 구분되며, 고리 1, 2, 3, 4호기, 영광 1, 2호기 및 울진 1, 2호기처럼 미국 웨스팅하우스사와 프랑스 프라마톰사가 공급한 원전은 이동식 측정 방식을 채택하고 있고, 그밖에 미국 CE사가 공급한 원전 및 한국 표준형 원전은 고정식 측정 방식을 채택하고 있다. 이동식의 경우 측정 설비의 검출기 구동시스템은 원자로 내부에 설치되어 있는 심블에 검출기를 삽입 또는 인출하면서 검출기가 중성자 분포 정보를 취득한 수 있도록 기계적인 구동 메커니즘을 제공한다. 기존 설비는 협소한 공간에 통로선택기를 복층으로 배치하여 검출기가 지나가는 통로의 구배가 심한 관계로 마찰이 커져 구동설비에 잦은 고장이 발생하였고, 구조적으로도 신뢰성이 떨어지는 문제점을 갖고 있었다. 본 논문에서는 신뢰성이 높고 통로에서의 마찰이 적은 새로운 개념의 이중색인 통로선택기와 구동장치의 설계와 제작 및 적용 결과 등을 다룬다.

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Evaluation of Operational Conditions and Power Consumption of a Bioattritor for Enzymatic Saccharification of Uncooked Starch (무증자 전분당화용 분쇄마찰매체 함유 효소반응기의 조작조건과 동력소모의 검토)

  • 이용현;박진서
    • Microbiology and Biotechnology Letters
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    • v.17 no.4
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    • pp.349-357
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    • 1989
  • Uncooked starch can be effectively saccharified in an enzyme reaction system containing attrition-milling media. To develope the high efficiency bioattritor, an agitated bead type bioreactor was constructed, and its effectiveness was evaluated. The optimal operation condition of bioattritor was found to be 300 g glass bead/L, 200 rpm, standard type impeller for 220 g/L of uncooked corn starch. The torque under the various operational conditions were also measured. The interrelation-ship between energy consumption for agitation of attrition-milling media and enhanced extent of saccharification of uncooked starch was evaluated, Power consumption was measured to be around 1.53 watt/L under the optimal operation condition. The attrition coupled enzyme reaction system is identified to tie a very excellent energy saying process for saccharification of uncooked starch, and seems to have a bright prospect of industrial application.

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