• Journal of the KSME
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• v.29 no.2
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• pp.125-137
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• 1989

구름접촉 피로는 반복적인 구름 접촉에 의해 나타나는 것으로서 피로의 원인이 되는 반복 하중이 두 물체의 반복적인 접촉에 의해서 일어난다는 점 때문에 일반적으로 피로연구 분야에서 다루 어지지 않고 마멸, 마찰 연구 분야에서 다루어지고 있다 구름접촉 피로현상이 나타나는 실제 예로서 베어링, 철도레일 등이 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.48-48
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• 2000

진공부품에 사용되고 있는 재료는 여러 가지 있으나 회주철품은 진동 감쇄 및 흡진성이 우수하여 소음 발생이 적고, 조직 중에 흑연이 존재하므로 주강에 비하여 자기윤활작용이 있으며, 말차계수가 적어 마찰면의 면입이 높은 경우에도 소손 등의 이상 마멸현상이 적어 진공펌프, 내연기관, 공작 기계등과 같이 강인성과 내마멸성을 요구하는 부품에 많이 이용되어 왔다, 이 회주철도 대별하면 여러 종류가 있고, 진공 펌프용 재질은 주로 회주철 중에 ASTM A형으로 도면에 명기되어 있다. 따라서 본 제품을 개발하는 과정중에 연속 주조법으로 제조된 ASTM형이 기존의 재료에 비하여 내기밀성, 내마면성, 내피로성 및 기계적 성질등이 우수함을 확인하여본 재질로 개발하였고, 시험한 연구 결과를 발표하고자 한다. 실험은 ASTM A형으로 주조하기 위하여 용해된 용탕을 사형 주형에서 GC200으로 주조하고, ASTM D형은 D사의 연속 주조기에서 직경 30mm로 주조하였다. 이와 같이 주조된 사료를 일정한 크기로 시험편을 만들어 인장 강도, 경도, 피로한도, 피로성, 절삭성, 내유압성, 소입성과 내마멸성을 시험하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.117-117
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• 2004

일반적으로 접촉 피로 마멸은 구름 또는 미끄럼 접촉시 작용하는 반복 응력에 의해 표면과 표면 아래에 균열이 형성되고 성장 및 합체의 과정을 거쳐 표면의 일부가 떨어져 나가는 손상으로 기어나 캠-롤러, 구름 베어링과 같이 구름-미끄럼 접촉상태로 운전하는 기계요소에서 가장 중요하게 고려되어야 할 파손 메커니즘이다. 특히 기어나 구름 베어링 같이 고주기 접촉 피로 특성을 지니는 기계요소의 수명은 피로수명 실험과 통계적 기법을 이용한 Weibull 이론을 기초로 한 수명식을 대부분 사용하고 있다.(중략)

• Tribology and Lubricants
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• v.29 no.6
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• pp.366-371
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• 2013

Various heat treatment and surface coating methods have been applied to machine parts. Nowadays, diamond-like carbon (DLC) coatings are widely used because of their excellent tribological characteristics. Despite the numerous studies on DLC-coated engineering surfaces, the exact wear mechanisms related to the coating thickness and elastic modulus have not been fully examined. In this study, a sliding contact problem between a small spherical hard particle and a DLC-coated steel surface is analyzed using a nonlinear finite element code, MARC. The maximum principal stress distributions and deformed surfaces are compared for different coating thicknesses and Young's modulus values. Plastically deformed surface shapes such as a groove and torus indicate that the most dominant wear mechanism for a DLC-coated surface is abrasive wear. Fatigue wear can also play a role in a case where the coating thickness is relatively large and the elastic modulus is high.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1269-1276
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• 2001

In case of contact fatigue, the accurate calculation of surface tractions and subsurface stress is essential to the predication of crack initiation life. Surface tractions influencing shear stress amplitude have been obtained by contact analysis based on influence function. Subsurface stress has been obtained by using rectangular patch solutions. In this study, to simulate asperity contact under sliding condition, the tip of asperity was simulated by sphere and to calculate crack initiation life in the substrate, dislocation pileup theory was used.

• Tribology and Lubricants
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• v.28 no.6
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• pp.283-288
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• 2012

In this study, a new sliding contact problem involving an elastomeric seal, a spherical particle and a hard coated steel counterface was modeled to investigate the detailed wear mechanisms related to the sealing surface. The model was also used to design the optimum coating conditions. A three-dimensional finite element contact problem was modeled and analyzed using the nonlinear finite element code, MARC. The deformed steel surface and stress distributions are presented for different coating layers and thicknesses. When the coating thickness is relatively small, the entrapped particle produces surface plastic deformations such as groove and torus. In addition, the sealing surface can be damaged by abrasive wear as well as fatigue wear. For a relatively thick and multi-layered coating, on the other hand, surface plastic deformation does not occur, and the amount of abrasive and fatigue wear is reduced. Therefore, the proposed contact model and results can be used in the design of various sealing systems, further intensive studies are required.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.161-166
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• 2010

Elastomeric seals are widely used in dynamic seal applications, and it is well known that the sealing surfaces can be gradually worn out. Abrasive wear is known to be the most dominant factor; however, little research has been carried out on this problem until now. In this study, a new contact problem related to elastomeric seals-a small spherical particle and steel surface-was modeled and analyzed using MARC. Variations of von-Mises and residual stress distributions as well as deformed seal and steel surface shapes with seal materials and interferences are presented. The stress distribution and surface deformation are highly affected by the elastic properties of seal. For PTFE, the maximum von-Mises stress exceeds the yield strength, and plastic deformation occurs on the steel surface. Therefore, the sealing surface can also be worn down by sub-surface fatigue due to intervening hard particles in the sealing surfaces together with the well-known abrasion.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.10a
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• pp.163-167
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• 1996

The life of rolling elements depends on various factors such as operating conditions and material properties. In this work, the effect of microstructure on the rolling behavior is investigated. Specially, the deformations in the substrate regions before and after rolling are compared. It is found that rolling action causes severe flow of material in the direction opposite to the rolling direction in the case of dry rolling direction. With lubrication, the deformation is more severe at the subsurface region rather than at the surface.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.11a
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• pp.13-18
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• 2002

증기 발생기 전열관의 파열 사고는 지난 20년 동안 2년마다 1개씩의 비율로 발생되어왔고 최근 몇 년간은 매년 발생되고 있는 추세이다(3). 전열관의 파열 사고는 응력부식균열, 피로 그리고 마멸 등의 원인에 의해서 발생되고 있는 것으로 알려져 있다. 초기 발전소에서 균열의 발생 및 성장은 축 방향 균열에 국한하여 관심을 가졌었으나 최근 원주 방향 균열에 의한 사고가 발생되면서 원주 방향 균열에 대해 관심을 가지게 되었다.(중략)