• 제목/요약/키워드: Fatigue Reliability

검색결과 543건 처리시간 0.024초

스플라인 커플링의 프레팅 마멸 예측에 관한 연구 (A Study on Estimating of Fretting Wear of a Spline Coupling)

  • 김응진;이상돈;조용주
    • Tribology and Lubricants
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    • 제25권4호
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    • pp.256-260
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    • 2009
  • Fretting is a kind of wear which effects on reliability and durability. When machine parts are joined joint in parts such as a bolt or a rivet or a pin, fretting phenomenon is occurred by micro relative movement. When fretting occurs in joint parts, there is wear which is the cause of fatigue crack. Recently, although the ways of assessment of fatigue and damage tolerance are established, there is no way to evaluate fatigue crack initiation life by fretting phenomenon. Consequently, the prediction of life and prevention plan caused by fretting are needed to improve reliability. The objective of this paper is to predict fretting wear by using a experimental method and contact analysis considering wear process. For prediction of fretting wear volume, systematic and controlled experiments with a disc-plate contact under gross slip fretting conditions were carried out. A modified Archard equation is used to calculate wear depths from the contact pressure and stroke using wear coefficients obtained from the disc-plate fretting tests.

플라스틱 BGA 솔더접합부의 고신뢰성에 관한 연구 (A Study of the High Reliability in Plastic BGA Solder Joints)

  • 김경섭;신영의;이혁
    • Journal of Welding and Joining
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    • 제17권3호
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    • pp.90-95
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    • 1999
  • The increase in high speed, multi-function and high I/O pin semiconductor devices highly demands high pin count, very thin, and high density packages. BGA is one of the solutions, but the package has demerits in package reliability, surface mounting problems due to the PCB warpage and solder joint crack related with TCE mismatch between the materials. On this study to verify the thermal fatigue lifetime of the solder joint FEM and experiments were performed after surface mounting BGA with different solder composition and reliability conditions. FEM showed optimum composition of Ag3.2-Sn96.5 and under the composition minimum creep deformation of the solder joint was calculated, and the thermal fatigue lifetime was improved. In view of temperature cycle condition, the conditions of $-65^{\circ}C$to $150^{\circ}C$ showed minimum lifetime and t was 1/3 of $0^{\circ}C$ to $125^{\circ}C$ condition. Test board was prepared and solder joint crack was verified. Until 1000cycle on soder joint crack was observed.

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콘크리트 휨피로수명의 확률분포 (Probabilistic Distributions of Fatigue Life of Concrete Subjected to Flexural Loading)

  • 오병환;이희택
    • 대한토목학회논문집
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    • 제6권2호
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    • pp.103-109
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    • 1986
  • 본(本) 논문(論文)에서는 작용되는 피로하중의 크기에 따른 콘크리트의 피로수명분포를 연구(硏究)하였다. 콘크리트보에 대하여 휨피로 실험을 수행하였으며, 피로응력의 크기는 세 가지로서 정적휨강도의 각각 85%, 75% 및 65%로 하여 피로수명을 측정하였다. 본 연구의 실험결과 피로하중의 크기에 따라 확률분포함수의 형태가 비교적 크게 달라짐을 발견하였으며, 이것은 콘크리트의 피로신뢰해석시 피로하중의 크기에 대한 영향을 고려해야 함을 말해 주고 있다. 분포매개변수의 결정은 도식법, 모멘트법 및 Maximum Likelihood 방법에 의거하였다. 콘크리트의 휨피로수명의 Weibull 분포(分布) 형상매개변수는 하중의 크기에 따라 2.0~4.0의 범위에 있는 것으로 나타났다.

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자동차 방진고무부품의 피로수명 예측 및 평가 (A Study on the Fatigue Life Prediction and Evaluation of Rubber Components for Automobile Vehicle)

  • 우창수;김완두;권재도
    • 한국자동차공학회논문집
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    • 제13권6호
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    • pp.56-62
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    • 2005
  • The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. Fatigue lifetime prediction methodology of the rubber component was proposed by incorporating the finite element analysis and fatigue damage parameter from fatigue test. Finite element analysis of 3D dumbbell specimen and rubber component were performed based on a hyper-elastic material model determined from material test. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. Fatigue life of the rubber component are predicted by using the fatigue damage parameter at the critical location. Predicted fatigue lifes of the rubber component agreed fairly well the experimental fatigue lives.

시간에 따른 부식열화가 고려된 피로취약도 곡선을 이용한 강교의 손상 평가 (Damage Estimation of Steel Bridge Members by Fatigue Vulnerability Curves Considering Deterioration due to Corrosion with Time)

  • 김효진;이형철;전석기;이상호
    • 한국방재학회 논문집
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    • 제7권4호
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    • pp.1-12
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    • 2007
  • 본 연구에서는 강교 부재를 대상으로 시간에 따른 부식과 교통량(트럭통행량)의 변화 영향을 반영한 피로 취약도 평가 방법을 제안하였다. 제안된 방법을 통해 부식과 교통량 변화를 고려할 수 있는 피로에 대한 한계상태함수를 설정하였다. 부식의 영향은 평균부식깊이와 피로강도감소계수와의 관계를 이용하여 한계상태함수에서 피로저항의 감소로써 반영되었다. 트럭통행량의 변화는 세 가지 대표적인 변화양상을 설정하여 기간별로 실제 변화에 맞게 모델링함으로써 한계상태함수에서 하중의 증가로 반영되었다. Monte-Carlo 시뮬레이션을 이용하여 신뢰성 해석을 수행하도록 하였으며, 이를 바탕으로 시간이력 피로 취약도 곡선을 도출하였다. 검증예제와 실제 국내 강교에 적용하여 제안된 피로 취약도 평가방법을 검증하였다.

원자력 구조재 신뢰성 향상을 위한 열피로 균열 시험편 제작 기법 개발 (Development the Technique for Fabrication of the Thermal Fatigue Crack to Enhance the Reliability of Structural Component in NPPs)

  • 김용;김재성;이보영
    • Journal of Welding and Joining
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    • 제26권2호
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    • pp.43-49
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    • 2008
  • Fatigue cracks due to thermal stratification or corrosion in pipelines of nuclear power plants can cause serious problems on reactor cooling system. Therefore, the development of an integrated technology including fabrication of standard specimens and their practical usage is needed to enhance the reliability of nondestructive testing. The test material was austenitic STS 304, which is used as pipelines in the Reactor Coolant System of a nuclear power plants. The best condition for fabrication of thermal fatigue cracks at the notch plate was selected using the thermal stress analysis of ANSYS. The specimen was installed from the tensile tester and underwent continuos tension loads of 51,000N. Then, after the specimen was heated to $450^{\circ}C$ for 1 minute using HF induction heater, it was cooled to $20^{\circ}C$ in 1 minute using a mixture of dry ice and water. The initial crack was generated at 17,000 cycles, 560 hours later (1cycle/2min.) and the depth of the thermal fatigue crack reached about 40% of the thickness of the specimen at 22,000 cycles. As a results of optical microscope and SEM analysis, it is confirmed that fabricated thermal fatigue cracks have the same characteristics as real fatigue cracks in nuclear power plants. The crack shape and size were identified.

1100℃급 가스터빈 동익의 무고장시험을 통한 HCF 신뢰성 평가 (Success Run Test for Reliability Demonstration of 1100℃ Gas Turbine Blades)

  • 이두영;구재량;김두수;김동환
    • KEPCO Journal on Electric Power and Energy
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    • 제3권2호
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    • pp.107-111
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    • 2017
  • $1100^{\circ}C$급 가스터빈 동익의 국산화 개발품에 대한 신뢰성을 무고장시험법에 의해 평가하였다. 터빈 동익은 기동, 정지 중에 발생하는 공진 또는 유체유발진동을 겪는 등 터빈 운전 중 상시 다양한 동하중에 노출되어 있으며, 이러한 변동하중은 터빈 동익에 고주기피로손상을 초래한다. 특히 동익의 파손에 의한 사고는 타 설비로의 파급이 크고, 막대한 경제적 피해를 야기하기 때문에, 발전소의 안정적인 운전을 위해 동익의 신뢰성이 우선 검증되어야 한다. 동익에 균열을 일으키기 위해서 전자식 가진기를 이용하여 공진에 의한 증폭된 동하중을 부과하였다. 가스터빈 동익의 수명분포를 와이블 분포로 가정하여 를 시험 시간을 계산하고, 시료 1개의 고장을 허용하는 조건으로 총 5개의 개발품을 대상으로 시험을 수행하여, 개발품 동익의 목표 수명을 90% 신뢰도로 보증할 수 있다는 것을 90% 신뢰수준에서 확인하였다.

표면균열무해화 기법에 의한 SKD61의 신뢰성 향상 (Improving Reliability of SKD61 Using Nondamaging Technology)

  • 이금화;구경희;김재훈;윤서현;권영국;남기우
    • 한국산업융합학회 논문집
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    • 제25권5호
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    • pp.791-797
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    • 2022
  • Using the fatigue limit (△σunsm) and residual stress (σr) of the UNSM smooth specimen, the harmless maximum crack depth (αhml) according to the crack aspect ratio (As) was evaluated. αhml evaluated the reliability in the relationship between the minimum crack depth (αNDI1, αNDI2) detectable by nondestructive inspection(NDI) and the crack depth (α25, α50) that reduces the fatigue limit by 25% and 50%. All αhml was determined by the crack depth. The αhml of 80N UNSM with high σr and high △σunsm was found to be large. σr in the depth direction had a much effect on αhml. Since αhml50(As=0.6-0.1) and αhml25, α25 and α50(some range) can secure the safety and reliability. Since αhml50 (As=1. 0-0. 6), it cannot be made harmless by UNSM. So safety and reliability cannot be secured. αNDI1 and αNDI2 are larger than α25, α25 cannot be detected by NDI. αNDI1 and αNDI2 are smaller than α50, α25 can detected by NDI.

SM20C 강의 피로파괴인성치의 확률분포 특성에 관한 연구 (A Study on Characteristic of Probabilistic Distribution of Fatigue Fracture Toughness in SM20C steel)

  • 오환교
    • 한국안전학회지
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    • 제12권3호
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    • pp.3-9
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    • 1997
  • The strength of material is scattered owing to the inhomogenity of microstructure, in spite of the same material. Therefore, in order to design the mechanical structure with the reliability engineering, it is important to grasp the statistic nature of material strength. In this paper, effects of grain sizes for the statistical nature of the fatigue crack growth was discussed. And the statistical of mechanical properties was compared with statistical nature of the fatigue crack growth rate.

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