• Title/Summary/Keyword: contact surface

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Finite Element Simulation of Surface Pitting due to Contact Fatigue (접촉피로에 의한 표면피팅의 유한요소 시뮬레이션)

  • Rhee, Hwan-Woo;Kim, Sung-Hun
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.3
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    • pp.80-88
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    • 2010
  • A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

Discussion on Rolling Contact Fatigue with Wear Amount by X-ray Reflection (마멸량의 대소에 따른 구름접촉 피로의 X선적 해석)

  • 이한영
    • Tribology and Lubricants
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    • v.10 no.3
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    • pp.71-77
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    • 1994
  • Rolling friction test was carried out to investigate the effect of the wear amount on rolling contact fatigue process in lubrication oil. The methods of this process were conducted at two Hertzian contact pressure and three slide ratio in each case by employing normalized and annealed carbon steel. During process of the rolling contact fatigue, the number of rotation until surface damage was occurred, the wear amount of rolling contact surface, and residual stress and half-value breadth using X-ray reflection on rolling contact surface were investigated. The result of this study shows that rolling contact fatigue process was directly influenced by wear trend and was confirmed by change of residual stress and half-value breadth on rolling contact surface.

A Safety about the Pipe Joint with Nonlinear Property (비선형 특성을 갖는 파이프 연결부에 대한 안전성)

  • Cho, Jae-Ung;Han, Moon-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.6 no.2
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    • pp.3-8
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    • 2007
  • Nonlinear property and contact matter are analyzed about the pipe applied with internal pressure through this study. The weakest part and its safety can be examined. Maximum equivalent stress is shown at the contact surface between bolt and nut. The value of contact stress with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The maximum contact pressure is shown at the clamp corner of the external surface on pipe. The value of contact pressure with the pressure of 12MPa is increased 1.4 times as large as that with no pressure. The radial deformation with no pressure is also increased greatly at the middle part of internal surface on pipe. But this maximum deformation on pipe with the pressure of 12MPa is shown at the part far away the support of pipe. This value is increased 5.7 times as large as that value with no pressure. As contact status, the sticking occurs most at the external surface of pipe. It also tends to occur at the contact surface between bolt and nut. At the external surface of pipe, the sticking in case of the pressure of 12MPa occurs more than that in case of no pressure.

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An Experimental Study on the Effects of Contact Angle on a Falling Liquid Film (접촉각이 유하액막 특성에 미치는 영향에 관한 실험적 연구)

  • Kim, Kyung-Hee;Kang, Byung-Ha;Lee, Dae-Young
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.11
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    • pp.867-873
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    • 2006
  • Vertical falling liquid film is extensively used in heat and mass transfer processes of many applications, such as evaporative coolers, cooling towers, and absorption chillers. In such cases, it is required that the falling film spreads widely in the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film or hydrophilic surface treatment affects the fluid physical properties of the film. Surfactant addition not only decreases contact angle between the liquid and solid surface but also changes the surface from hydrophobicity to hydrophilicity. In this study, the effects of contact angle on falling film characteristics over a vertical surface have been investigated experimentally. The contact angle is varied either by an addition of surfactant to the liquid or by hydrophilic surface treatment. It is found that the wetted area is increased and film thickness is decreased by the hydrophilic treatment as compared with those of other surfaces. With this hydrophilic treatment, the falling liquid film spreads out widely in the surface. As surfactant concentration is increased, wetted area is also increased and the film thickness is substantially decreased.

Sliding Contact Analysis between Rubber Seal, a Spherical Particle and Steel Surface (시일과 스틸면 사이에 구형 입자가 있는 미끄럼 접촉 해석)

  • Park, Tae-Jo;Lee, Jun-Hyuk
    • Tribology and Lubricants
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    • v.28 no.1
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    • pp.1-6
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    • 2012
  • In this paper, a three elastic body sliding contact problem is modeled to investigate more precise wear mechanisms related with the sealing surface. A 3-D finite element contact model, a small spherical elastic particle, PTFE seal and steel surface, is solved using a nonlinear finite element code MARC. The deformed seal and steel surface shapes, von-Mises and principal stress distributions are obtained for different seal sliding distances. The entrapped small particle within PTFE seal results in very high stresses on the steel surface which exceeded its yield strength and produce plastic deformation such as groove and torus. The sealing surface could also be worn down by sub-surface fatigue due to intervening small particles together with the well-known abrasive wear. Therefore the proposed contact model adopted in this paper can be applied in design of various sealing systems, and further studies are required.

Sub­surface Stress Distribution beneath the Contact Surface of the Gear Teeth for Two Profile Models (치면 프로파일 모델에 따른 기어 치면 내부의 응력 분포)

  • 구영필;오명석;김형자;김영대
    • Tribology and Lubricants
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    • v.19 no.6
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    • pp.357-364
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    • 2003
  • The sub­surface stress field beneath the gear's contact surface caused by the contact pressure in lubricated condition has been calculated. To evaluate the influence of the clearance shape on the stress field, two kinds of tooth profile models were chosen. One is the conventional cylinder contact model and the other is the new numerical model. Love's rectangular patch solution was used to obtain the sub­surface stress field. The analysis results show that the sub­surface stress is quite dependent on both the contact pressure and the profile model. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

Surface Characteristics of Silicone Rubber Processes by Corona Discharges (코로나 방전에 따른 실리콘 고무의 표면 특성)

  • 한동희;조한구;강동필;민경은
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.2
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    • pp.133-140
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    • 2002
  • This paper aims to investigate the effect of silicone oils as processing agent affecting the loss and recovery of hydrophobicity. The recovery of hydrophobicity was evaluated by the measurement of the surface electrical resistivity and the contact angle on the SIR surface. Two kinds of silicone oils (1 and 2) having different molecular weight were selected under a consideration of hydrophobicity and processability. SIR specimens were exposed to corona discharges in air and the specimens were analyzed with contact angle and surface resistance measurements. It was observed that the contact angle and the surface resistivity of SIR increase gradually with testing time. The fast recovery of hydrophobicity of SIR, expressed by the increment of contact angle and surface resistivity, was showed in SIR2 containing silicone oil 2.

A study on lubrication Properties of a Dimple Pattern using an Average Flow Analysis with a Contact Model of Asperities (돌기 접촉 모델과 평균 유동 분석을 이용한 딤플 패턴의 윤활 특성에 관한 연구)

  • Kim, Mi-Ru;Lee, Seung-Jun;Li, Liang;Lee, Deug-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.6
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    • pp.41-49
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    • 2016
  • To evaluate lubrication properties by surface roughness under boundary and mixed lubrication, a new approach is suggested by both asperity flow and contact with stochastic characteristics. Many researchers already have studied the effect of surface roughness on flow. But, it has become important to research of the phenomenon of asperities contact in surfaces because the growth of asperities contact area under heavy load conditions. In this paper, flow factors in the average flow model derived by Patir and Cheng were used, and a multi-asperity contact model was included to calculate lubrication properties of a surface with a randomly generated rough surface. A numerical analysis using the average Reynolds equation with both the average flow model and the asperity contact model was conducted, and the results were compared with those from previous research. The results showed that the influence of asperities on lubrication and the friction coefficient changed rapidly on application of contact model.

Measuring System of Surface Roughness for On-The-Machine using Diffraction Light (회절광을 이용한 기상계측용 표면거칠기의 측정시스템)

  • 김성훈;이기용;강명창;김정석;김남경
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.05a
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    • pp.803-807
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    • 2000
  • This paper deals wi th the establishment of the method of non-contact surface roughness measurement by developed system. One of the most Important factor of determinating quality of a produced manufacture is surface roughness The tendency of manufacturing method is changing from small amount manufactures / high-volume production to large amount manufactures / low volume production, and the study of reducing time for surface roughness measurement has been actively investigated The non-contact surface roughness method by using laser which is different from contact method has been only used to the polished surface, so new surface roughness measurement method was adopted by virtue of Fraunhofer diffraction in the periodic surface for on-the-machine. in this paper, we establish the method of non-contact surface roughness measurement which can reduce measuring time in the periodic surface

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Study on the effect of the surface rolling condition to the surface roughness (표면 Rolling시 작업조건이 표면조도에 미치는 영향)

  • 강명순;김희남
    • Journal of the korean Society of Automotive Engineers
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    • v.8 no.3
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    • pp.68-76
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    • 1986
  • The surface rolling method which is one of the plastic deformation processes increases the surface roughness and hardness of materials. In this study, three NACHI6000 ZZ bearing were used for surface rolling tool on the mild steel and high carbon steel. The purpose of this study is to investigate the effects of rolling speed, feed rate and contact pressure on the surface roughness. The following results have been obtained with the mild steel and high carbon steel. 1. The roller finishing method has increased surface roughness from 2.4 .mu.m Ra at initial ground surface to 0.17 .mu.m Ra-0.4 .mu.m Ra. 2. The contact pressure has influenced greatly on the surface roughness. There is an optimal contact pressure. 3. As the rolling speed and the feed rate decrease, the surface roughness improves. 4. The optimal contact pressure for the good surface roughness of SS40 and STC 3 has been at 213 Kgf/Cm$^{2}$ and 220 Kgf/Cm$^{2}$ respectively.

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