• Title/Summary/Keyword: Area contact

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Optimized Sealing Profile Design of Mechanical Face Seals for a Hydro-power Turbine (소수력 터빈용 기계평면시일의 최적형상설계에 관한 연구)

  • Kim, Chung-Kyun;Kim, Jung-Il;Sihn, Ihn-Cheol;Lim, Kwang-Hyeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.06a
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    • pp.499-502
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    • 2006
  • This paper presents computed results of FEM analysis on the tribological contact behaviors of a primary sealing components of mechanical face seals for a small hydro-power turbine. The FEM computed results present that the contact area between seal rings and seal seats is very important for a good tribological performance such as low friction heating, low wear, high contact normal stress in a primary seal ing components. Based on the FEM computation, model III in which has a small sealing contact area shows low dilatation of primary sealing components, and high contact stress between a seal ring and a 1)seal seat.

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The Evaluation of Fretting Fatigue Behavior on Rotary Bending Fatigue for Railway Axle Material (회전굽힘 피로 하에서의 철도 차축재료 프레팅 피로거동 평가)

  • Choi, Sung-Jong;Kwon, Jong-Wan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.2
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    • pp.74-82
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    • 2010
  • Fretting damage can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these test, the following results are obtained: 1) it is found that the fretting fatigue limit of standard specimen decreased about 37% compared to the plain fatigue limit. 2) The early crack of Shinkansen type specimens initiated in contact area and final fractured below samp=214 MPa. 3) The early crack of all TGV type specimens initiated in rounded area and fractured. 4) Tire tracks and rubbed scars were observed in the oblique crack region and fatigue crack growth region of fracture surface. 5) The wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.

Finite Element Analysis of Pivot Stiffness for Tilting Pad Bearings and Comparison to Hertzian Contact Model Calculations (유한 요소 해석을 통해 계산된 틸팅 패드 베어링의 피봇 강성과 Hertzian 접촉 모델 해석 결과 비교)

  • Lee, Tae Won;Kim, Tae Ho
    • Tribology and Lubricants
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    • v.30 no.4
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    • pp.205-211
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    • 2014
  • Recent studies emphasize the importance of pivot stiffness in the analysis of tilting pad bearings (TPBs). The present paper develops a finite element model of the pad pivot and compares the predicted pivot stiffness to the results of Hertzian contact model calculations. Specifically, a finite element analysis generates tetrahedral mesh models with ~40,000 nodes for a ball-socket pivot and ~50,000 nodes for a rocker-back pivot. These models assume a frictionless boundary condition in the contact area. Increasing the applied loads on the pad in conjunction with increasing time steps ensures rapid convergence during the nonlinear numerical analysis. Predictions are performed using the developed finite element model for increasing the differential diameters between the pad pivot (or ball) and the bearing housing (or socket). The predictions show that the pivot contact area increases with decreasing differential diameters and increasing applied loads. Further, the maximum deformation occurring at the pivot center increases with increasing differential diameters and increasing applied loads. The pivot stiffness increases nonlinearly with decreasing differential diameters and increasing applied loads. Comparisons of results of the developed finite element model to those of Hertzian contact model calculations assuming a small contact area show that the latter model underestimates the pivot stiffnesses predicted by the finite element models of the ball-socket and rocker-back pivots, particularly for small differential diameters. This result implies the need for cautionduring the design of pivot stiffness by the Hertzian contact model.

Comparision Analysis of Model Test for Prediction of Uplift Resistance in the Reclaimed Land Greenhouse Foundation (간척지 온실기초 나무말뚝의 인발저항력 예측을 위한 실내모형시험 결과 비교·분석)

  • Song, Chang Seob;Kim, Myeong Hwan;Jang, Ung Hee
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.2
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    • pp.45-52
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    • 2016
  • The object of this paper was to evaulate modified proposed design equation in model test result in order to estimate uplift-resistance of timber pile of reclaimed land greenhouse foundation. Uplift resistance result of model test was increased to according to increased of contact area. Uplift-resistance result of field test tend to lineary increased to according to increased of embedment depth and contact area. Results of field uplift-resistance was evaluate compare with modified proposed design equation results of model test and Effective stress method. As the Effective stress method tend to underestimate, modified proposed design equation results of model test tend to similar type. As the contact area increase, difference between field uplift-resistance results and modified proposed design equation results of model test was considered uplift-speed.

Nano/Micro Friction with the Contact Area (접촉 면적에 따른 나노/마이크로 마찰 특성)

  • Yoon Eui-Sung;Singh R. Arvind;Kong Hosung
    • Tribology and Lubricants
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    • v.21 no.5
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    • pp.209-215
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    • 2005
  • Nano/micro friction with the contact area was studied on Si-wafer (100) and diamond-like carbon (DLC) film. Borosilicate balls of radii $0.32{\mu}m,\;0.5{\mu}m,\;1.25{\mu}m\;and\;2.5{\mu}m$ mounted on the top of AFM tip (NPS) were used for nano-scale contact and Soda Lime glass balls of radii 0.25mm, 0.5mm, 1mm were used for micro-scale contact. At nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at micro scale it was measured using ball-on flat type micro-tribotester. All the experiments were conducted at controlled conditions of temperature $(24\pm1^{\circ}C)$ and humidity $(45\pm5\%)$. Friction was measured as a function of applied normal load in the range of 0-160nN at nano scale and in the range of $1000{\mu}N,\; 1500{\mu}N,\;3000{\mu}N\;and\;4800{\mu}N$ at micro scale. Results showed that the friction at nano scale increased with the applied normal load and ball size for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for Si-wafer at micro scale. However, for DLC friction decreased with the ball size. This difference of in behavior of friction in DLC nano- and microscale was attribute to the difference in the operating mechanisms. The evidence of the operating mechanisms at micro-scale were observed using scanning electron microscope (SEM). At micro-scale, solid-solid adhesion was dominant in Silicon-wafer, while plowing in DLC. Contrary to the nano scale that shows almost a wear-less situation, wear was prominent at micro-scale. At nano- and micro-scale, effect of contact area on the friction was discussed with the different applied normal load and ball size.

Molecular Simulation Study on Influence of Water Film Thickness on Lubrication Characteristics (물 분자막의 두께와 윤활특성의 상관관계에 대한 분자시뮬레이션 연구)

  • Kim, Hyun-Joon;Heo, Segon
    • Tribology and Lubricants
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    • v.38 no.5
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    • pp.199-204
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    • 2022
  • This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.

A Study on Decreasing of Sliding Noise of a Carbon Film Variable Resistor (탄소 피막 가변 저항기의 접동 잡음 감소에 관한 연구)

  • 윤재강
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.20 no.1
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    • pp.50-54
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    • 1983
  • Contact resistance variation which may be called sliding noise in carbon film variable resistors whose resistance elements consists of linear resistivity distribution were measured with several kinds of sliders and were analyzed to reduce the contact resistance variation. About the measuring method, the standard method of measuring contact resistance variation specified by the variable Resistance Components Institute was adupted. By analyzing the experimental results, it has been shown that the primary cause of contact resistance variation is due to current constriction and small discharge sparks in the resistance film in the area close to the slide contact. Moreover, it has been found that the sliding noise would be reduced by increasing the number of contact points, sliding speed, and pressure, and by using some kinds of insulation oil on the contacting surface. High contact resistance variation is likely to occur in the area of high resistance variation in a logrithmic resistance taper.

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A study on change in electric contact resistance of the tin-plated copper connector of automotive sensor due micro-vibration (차량용 주석 도금된 구리 커넥터에서 미세진동에 의한 전기접촉 저항변화에 관한 연구)

  • Yu, Hwan-Sin;Park, Hyung-Bae
    • Journal of Advanced Navigation Technology
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    • v.12 no.6
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    • pp.653-658
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    • 2008
  • The automotive environment is particularly demanding on connector performance, and is characterized by large temperature changes, high humidity and corrosive atmospheres. Fretting is a contact damage process that occurs between two contact surfaces. Fretting corrosion refers to corrosion damage at the asperities of contact surfaces. This damage is induced under load and in the presence of repeated relative surface motion, as induced for example by vibration. This paper critically reviews the works published previously on fretting corrosion of electrical connectors. Various experimental approaches such as testing machines, material selection, testing environments, acceleration testing techniques and preventing methods are addressed. Future research prospects arc suggested.

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A Study on the contact surface of Stem and Bellows of Gate Valve in Nuclear Power Plants (원자력발전소 게이트밸브의 스템 - 벨로우즈 접촉면에 관한 연구)

  • Ko, Seok-Hoon;Shim, Dong-Hyouk;Kim, Dae-Youl;Choi, Myung-Jin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1044-1048
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    • 2006
  • Nuclear power generation is very dangerous in occasion that skirt of structure by earthquake although it is high effective generation that can make a lot of energies with few raw material. when design, it must consider a lot of problems caused by an earthquake. The seismic analysis of the structure has been great concern in the engineering society with an effort to reduce the severe damages from an earthquake. So the earthquake resistant design is one of the crucial design procedures of a gate valve used in nuclear power generation. The gate valve which has the contact area between stem and bellows. Because of the contact area. The gate valve should be given high stress and frictional wear. In this thesis, Considering the gate valve which has some contact distance between stem and bellows. The gate valve which has some contact distance is analyzed by a commercial FEM code of Ansys and Then compared to the gate valve behavior which doesn't have contact distance.

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Searching Algorithm for Finite Element Analysis of 2-D Contact Problems (2차원 접촉문제의 유한요소 해석을 위한 탐색알고리즘)

  • 장동환;최호준;고병두;조승한;황병복
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.12
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    • pp.148-158
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    • 2003
  • In this paper, efficient and accurate contact search algorithm is proposed for the contact problems by the finite element method. A slave node and a maser contact segment is defined using the side of a finite element on the contact surface. The specific goal is to develop techniques of reducing the nonsmoothness of the contact interactions arising from the finite element discretization of the contact surface. Contact detection is accomplished by monitoring the territory of the slave nodes throughout the calculation for possible penetration of a master surface. To establish the validity of the proposed algorithm, some different process and geometries examples were simulated. Efforts are focused on the error rate that is based on the penetrated area through the simulations fur large deformation with contact surface between deformable bodies. A proposed algorithm offers improvements in contact detection from the simulation results.