• Title/Summary/Keyword: friction forces

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A study on the EHL film behavior measurement for the multigrade lubricant (멀티그레이드 윤활유의 탄성유체윤활 유막 측정 연구)

  • Jang Siyoul;Kim Seungjae;Kim Jaehong;Bae Daeyoon;Yoo SungChoon
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.269-274
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    • 2004
  • It is important to decide the minimum film thickness and viscosity variations of a multigrade lubricant in the contact surface under the high pressure conditions. By carrying out acceleration, deceleration, and various sliding-rolling ratio movement between two contact bodies, it is experimented that film formation variations in the contact surface are captured with multigrade lubricants in order to exactly investigate the variations of film formations. Optical interference images are continuously captured with high resolution CCD camera during the captured period of acceleration, deceleration. The friction forces between the contacting bodies are also measured simultaneously with the film formation.

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Use of Modern Microscopes in Analysing Fiber and Paper Properties (II)-New Aspect in Fibrillation of Pulp Fibers during Refining-

  • Kim, Chul-Hwan;Keigh R. Wadhams
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.3
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    • pp.60-67
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    • 1999
  • The CLSM and the image analysis technique enhanced observation of fiber wall fibrillation occurred in both the outer and the fiber wall surfaces during refining by non-destructive techniques. In the early stages of refining, it was well observed that a partial separation between the S1 and S2 layer in the secondary wall was made generating a space in the wet fiber walls . With further refining, it was clearly shown that the shear forces imparted by the refiner bar surfaces caused the S1 layer to become totally separated from the S2 layer as well as creating microfibrils. Furthermore, the fibrillation in the inner fiber wall surfaces could be due to the normal force (Fn) by refiner bars, friction force between a fiber and refiner bars (Fs) and inner friction force between fiber walls(fs). It was confirmed that the concept of fibrillation should be extended to fibrillation in the inner fiber wall surfaces as well as internal and external fribrillation.

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Shear Resistance Capacity of Precast Post-tensioned Concrete Beam-Column Connection (프리캐스트 포스트텐션 콘크리트 보-기둥 접합부의 전단성능)

  • 조경호;이종규;최광호;김상식
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10a
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    • pp.769-774
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    • 2000
  • The first thing in developing precast post-tensioned concrete frame system verify the shear resistance capacity of the beam-column connection at which the transfer of member forces become discontinuous. Complying with the necessity of such experimental research, shear tests have been performed for six test specimens which were cast and cured at Dong-Ah Concrete Manufacturing Company and post-tensioning at Concrete Laboratory of Inha University. Shear key and magnitude of post-tensioned force are taken test variables. From the test results, it has been observed that the shear resistance of the specimens attained to higher values than those of theoritical calculations based on the shear friction with shear friction coefficient being 0.6.

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Pore size effects of adhesion and friction for nanohoneycomb structures in AFM (원자현미경에서 나노허니컴 구조물의 홀 사이즈에 따른 점착 및 마찰 거동 분석)

  • Choi, Duk-Hyun;Lee, Pyung-So;Lee, Kun-Hong;Park, Hyun-Chul;Hwang, Woon-Bong
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.11a
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    • pp.129-132
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    • 2005
  • This study analyzes the behavior of adhesion and friction according to the pore size of nanohoneycomb structures in atomic force microscope (AFM). Anodic aluminum oxide (AAO) films are fabricated as nanohoneycomb structures. According to the pore diameters of the nanohoneycomb structures, the adhesive forces and the frictional coefficients arc obtained in AFM, and the behaviors are analyzed in the view of the contact area between the sphere particle and nanohoneycomb substrate. The effective Young's moduli of the nanohoneycomb structures are measured from the nanoindentation tests, and the contact areas at zero applied load are calculated by combining the porosity of the nanohoneycomb structures and the contact radius determined from JKR and DMT theory.

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Rotordynamic Analysis of Compressor Labyrinth Seals (압축기용 라비린스 실의 동특성 해석)

  • 하태웅;이안성
    • Journal of KSNVE
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    • v.8 no.5
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    • pp.849-855
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    • 1998
  • An analysis of lateral hydrodynamic forces of compressor labyrinth seals is presented. Basic equations are derived using a two-control-volume model for compressible flow. Blasius' wall friction-factor formula and jet flow theory are used for the calculaton of wall shear stresses and recirculation velocity in the cavity. Linearized zeroth-order and first-order perturbation equations are developed for a small motion about the centered position by expansion in the eccentricity ratio. Integraton of the resultant first-order pressure distribution over the seal defines the rotordynamic coefficients. As an application a rotordynamic analysis of the balance drum labyrinth seal found in an ethylene regrigeration copmressor is carried out. The rotordynamic characteristic results of the labyrinth seal are presented and compared with other types of seals, honeycomb seal and smooth seal.

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Seismic performance of a rocking bridge pier substructure with frictional hinge dampers

  • Cheng, Chin-Tung;Chen, Fu-Lin
    • Smart Structures and Systems
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    • v.14 no.4
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    • pp.501-516
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    • 2014
  • The rocking pier system (RPS) allows the columns to rock on beam or foundation surfaces during the attacks of a strong earthquake. Literatures have proved that seismic energy dissipated by the RPS through the column impact is limited. To enhance the energy dissipation capacity of a RPS bridge substructure, frictional hinge dampers (FHDs) were installed and evaluated by shaking table tests. The supplemental FHDs consist of two brass plates sandwiched by three steel plates. The strategy of self-centering design is to isolate the seismic energy by RPS at the columns and then dissipate the energy by FHDs at the bridge deck. Component tests of FHD were first conducted to verify the friction coefficient and dynamic characteristic of the FHDs. In total, 32 shaking table tests were conducted to investigate parameters such as wave forms of the earthquake (El Centro 1940 and Kobe 1995) and normal forces applied on the friction dampers. An analytical model was also proposed to compare with the tested damping of the bridge sub-structure with or without FHDs.

Dynamic Characteristics and Compressive Stress of Multi-Layered Structure (적층 구조물의 압축응력과 동적특성)

  • Shon, Ho-Woong;Lee, Sung-Min
    • Journal of the Korean Geophysical Society
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    • v.9 no.1
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    • pp.63-71
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    • 2006
  • When surveying the cultural heritages especially in the case of stone structures, preserving their originalstate is of primary importance. For the effective assessment of survey results of stone structure, thedynamic characteristics of that system should be considered. Dynamic characteristics of stone masonry structures depend on several factors such as coefficients of friction, contact conditions, and number of layers of bonding stones. These factors can be estimated by using the dynamic analysis results. This paper describes a method for natural frequency determination of traditional stone arch bridge subjected to compressive force. For this purpose, multi-layered granite brick models of for arch bridge were made and fundamental frequencies corresponding increasing axial forces were measured.

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The Effect of Reduction of Friction Heat by Micro Dimple on the Sliding Surface of Elastomer (탄성중합체 표면의 마이크로 딤플에 의한 발열저감효과)

  • Kim, Gun Wan;Yoo, Myung Ho;Lee, Taek Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.8
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    • pp.847-853
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    • 2013
  • Micro-dimples on sliding surfaces have been investigated to reduce the frictional forces on metal bearing surfaces; however, for an elastomer, such as thermoplastic polyurethane (TPU), this has not been studied. The material properties of an elastomer are affected by temperature, and this can shorten the life of the elastomer. In this paper, micro-dimples were applied on the surface of an elastomer in order to reduce the frictional heating, which was experimentally investigated using pin-on-disk apparatus while the surface temperature was measured. To obtain optimal design parameters, the design of the experiment was applied, and the shape of the section, size, depth and density of micro-dimples were selected as the design parameters. The results show that the size of the dimple is the most important design parameter.

Switched Reluctance Contact-Free Linear Actuator Using Attractive Magnetic Forces (자기 흡인력에 의한 비접촉식 SR 형 선형 구동기)

  • 이상헌;정광석;백윤수
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.10
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    • pp.47-55
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    • 2003
  • In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

Dynamic Characteristics of Journal Bearings Considering Bearing Span (베어링 Span을 고려한 저널 베어링의 동특성 해석)

  • 윤진욱
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.906-910
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    • 2003
  • This paper numerically analyzes the dynamic characteristics of a spindle system supported by two identical journal bearings considering bearing span that has dynamic load due to its mass unbalance. The Reynolds equation is transformed to solve a herringbone grooved journal bearing. The Reynolds equations are solved using FEM in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or angular displacement of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the same bearing spans of upper and lower journal bearings produce the minimum runout and friction torque of a spindle system.

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