• 제목/요약/키워드: strain controlled fatigue test

검색결과 32건 처리시간 0.025초

평균응력을 동반하는 2.2Ni-lCr-0.5Mo강의 피로수명과 변형률에너지 밀도와의 상관관계 (Correlation Between Fatigue Life of 2.2Ni-0.1Cr-0.5Mo Steel Accompanying Mean Stresses with Cyclic Strain Energy Density)

  • 고승기;하정수
    • 대한기계학회논문집A
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    • 제27권1호
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    • pp.167-174
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    • 2003
  • Fatigue damage of 2.2Ni-1Cr-0.5Mo steel used fir high strength pressure tubes and vessels was evaluated using uniaxial specimens subjected to strain-controlled fatigue loading. Based on the fatigue test results from different strain ratios of -2. -i 0, 0.5, 0.75, the fatigue damage of the steel was represented by using a cyclic strain energy density. Mean stress relaxation depended on the magnitude of the applied strain amplitude. The high pressure vessel steel exhibited the cyclic softening behavior. Total strain energy density consisting of the plastic strain energy density and the elastic tensile strain energy density described fairly well the fatigue life of the steel, taking the mean stress effects into account. Compared to other fatigue damage parameters, fatigue life prediction by the cyclic strain energy density showed a good correlation with the experimental fatigue lift within a factor of 3.

유지시간 효과를 고려한 12Cr 내열강의 열피로 및 저주기 피로 특성 (Thermal-Mechanical and Low Cycle Fatigue Characteristics of 12Cr Heat Resisting Steel with Hold Time Effects)

  • 하정수;고승기;옹장우
    • 한국자동차공학회논문집
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    • 제3권1호
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    • pp.1-12
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    • 1995
  • Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

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Fe-18Mn TWIP강의 Pre-strain에 따른 저주기 및 고주기 피로 수명 예측 모델 (A Prediction Model for Low Cycle and High Cycle Fatigue Lives of Pre-strained Fe-18Mn TWIP Steel)

  • 김용우;이종수
    • 소성∙가공
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    • 제19권1호
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    • pp.11-16
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    • 2010
  • The influence of pre-strain on low cycle fatigue behavior of Fe-18Mn-0.05Al-0.6C TWIP steel was studied by conducting axial strain-controlled tests. As-received plates were deformed by rolling with reduction ratios of 10 and 30%, respectively. A triangular waveform with a constant frequency of 1 Hz was employed for low cycle fatigue test at the total strain amplitudes in the range of ${\pm}0.4\;{\sim}\;{\pm}0.6$ pct. The results showed that low-cycle fatigue life was strongly dependent on the amount of pre-strain as well as the strain amplitude. Increasing the amount of prestrain, the number of reversals to failure was significantly decreased at high strain amplitudes, but the effect was negligible at low strain amplitudes. A new model for predicting fatigue life of pre-strained body has been suggested by adding ${\Delta}E_{pre-strain}$ to the energy-based fatigue damage parameter. Also, high-cycle fatigue lives predicted using the low-cycle fatigue data well agreed with the experimental ones.

고온 저주기 피로에 의한 STS 304 압연강재의 특성연구 (Characteristics of STS 304 Rolled Steel by High Temperature Low Cycle Fatigue)

  • 김치환;박영민;배문기;신동철;김대원;김태규
    • 열처리공학회지
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    • 제32권1호
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    • pp.12-16
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    • 2019
  • In this study, strain-controlled low cycle fatigue test for hot rolled STS304 steel was carried out at $400^{\circ}C$ and $600^{\circ}C$, respectively. High temperature fatigue test was done using an electric furnace attached on the hydraulic fatigue test machine. The results of this study show that STS304 hot rolled steel has excellent static strength and fatigue characteristics. The hysteresis loop at half life was obtained in order to calculate the elastic and plastic strain. Also, Relationship between strain amplitude and fatigue life was examined in order to predict the low cycle fatigue life of STS304 steel by Coffin-Manson equation.

304L 스테인리스 강 용접부의 저주기 피로 성능 평가 (Low Cycle Fatigue Performance of 304L Stainless Steel Weldments)

  • 황재현;오동진;이도영;전민성;김명현
    • Journal of Welding and Joining
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    • 제34권3호
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    • pp.47-51
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    • 2016
  • Recently, the market of liquefied natural gas is growing in accordance with shale gas development and environmentally friendly policies. Also, LNG is in the spotlight as an alternative fuel to previously used fossil fuel and the fuel for the ship to meet emission standards which takes effected by IMO (International Maritime Organization). According to growth of LNG, LNG carriers needs are also expected to increase significantly. This study investigates low cycle fatigue (LCF) performance of 304L stainless steel weldments to investigate fatigue performance in plastic strain region. 304L stainless steel is known to have improved fatigue performance at cryogenic conditions. LCF behavior are investigated by a strain-controlled condition up to 1% strain range and conducted with three different thickness (3mm, 5mm, 10mm). Also, test were performed with three different strain ratio R such as R = -1, -0, 0.5, Finally, the fatigue design curve for 304L stainless steel weldments at room tem- perature are proposed. Considering all test conditions, it is shown that LCF performance have similar tendency regardless of thickness and strain ratio. LCF design curve of 304L stainless steel weldments are lower than 304L stainless steel base metal.

외경홈을 지닌 C형 시험편의 저주기 피로수명평가 (Low Cycle Fatigue Life Evaluation of External Grooved C-shaped Specimen)

  • 이송인
    • 대한기계학회논문집A
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    • 제21권2호
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    • pp.199-208
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    • 1997
  • A local strain approach was applied to an external single and double grooved C-shaped specimen in order to evaluate and predict the fatigue crack initiation life by using low cycle fatigue properties. The low cycle fatigue properties were determined from the strain-controlled fatigue tests using smooth cylindrical axial specimens. Fatigue crack initiation life was evaluated by a life prediction software, FALIPS, based on the local strain approach. The fatigue life was significantly influenced by the mean stress, and SWT parameter represented the fatigue life effectively. The predicted fatigue crack initiation life was then compared to the experimental fatigue life evaluated from the C-shaped fatigue test specimens. A good correlation was found between the experimental and predicted fatigue lives within factors of 2 and 4 for the single and double grooved C-shaped specimens respectively. Also, experimental fatigue life of the double grooved specimen was 10-12 times longer than that of the single grooved specimen.

이종재료 레이저 용접 판재의 저주기 피로 특성 (The Low Cycle Fatigue Behavior of Laser Welded Sheet Metal for Different Materials)

  • 김석환;곽대순;김웅찬;오택열
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2005년도 추계학술대회 논문집
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    • pp.627-631
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    • 2005
  • In this study, low fatigue behavior of laser welded sheet metal were investigated. Before welding, the cross section of butt joint was prepared only by fine shearing without milling process. Specimens were same sheet metal and welding condition that using automobile manufacturing company at present. Butt joint of cold rolled sheet metal was welded by $CO_2$ laser. It is used that welding condition such as laser welding speed was 5.5m/sec and laser output power was 5kW for 0.8mm and 1.2mm sheet metal. The laser weldments were machined same or different thickness and same or different material. In order to mechanical properties of around welding zone, hardness test was performed. Hardness of welding bead is about 2 times greater than base material. We performed the low cycle fatigue tests for obtaining fatigue properties about thickness and the weld line direction of specimen. The results of strain controlled low cycle fatigue test indicate that all specimens occur cyclic softening, as indicated by the decrease in stress to reach a prescribed strain.

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축방향철근의 저주파 피로 거동 (Low Cycle Fatigue Behavior of Longitudinal Reinforcement)

  • 이재훈;고성현
    • 콘크리트학회논문집
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    • 제22권2호
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    • pp.263-271
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    • 2010
  • 이 연구는 국내에서 생산되고 있는 철근이 반복하중을 받는 경우의 파괴 특성에 대한 검증을 목적으로 한다. 이 논문은 철근콘크리트 하부구조(파일과 교각)에 배근된 축방향 철근에 대한 저주파 피로 거동을 다루었다. 전체 81개의 철근 실험체에 대하여 변형률 진폭에 따른 반복 축방향 변형률 제어 방식으로 저주파 피로 실험을 수행하였다. 실험 변수는 인장변형률과 압축변형률의 비율, 축방향 철근의 항복강도, 철근지름에 대한 철근길이의 비율, 철근의 크기와 변형률 진폭으로 선택하였다. 이 논문에서 실험 결과에 따른 저주파 피로 거동과 저주파 피로 수명을 분석하였다.

폴리아세탈 소재의 확률론적 변형률-수명선도 평가 (An Evaluation of Probabilistic Strain-Life Curve in Polyacetal)

  • 장천수;김철수;박범규;김정규
    • 대한기계학회논문집A
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    • 제30권11호
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    • pp.1417-1424
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    • 2006
  • In order to evaluate variation of fatigue life of mechanical components including engineering plastics, it is important to estimate probabilistic strain-life curves to accurately define the variation of fatigue characteristics. This paper intends to provide new assessment of P-$\varepsilon$-N (probabilistic strain-life curves) for considering the variation of fatigue characteristics in polyacetal. The fatigue strain controlled tests were conducted under constant 50% humidity and room temperature condition by a universal testing machine at strain ratio, R=0. A practical procedure is introduced to evaluate probabilistic strain-life curves. Three probabilistic distributions were used for generating P-$\varepsilon$-N curves such as normal, 2-parameter and 3-parameter Weibull. In this study, 3-parameter Weibull distribution was found to be most appropriate among assumed distributions when the probability distributions of the fatigue characteristic were examined using chi-square and Kolmogorov-Smirnov test. The more appropriate P-$\varepsilon$-N curves for these materials are generated by the proposed method considering 3-parameter Weibull distribution.

Detection of Low Cycle Fatigue in Type 316 Stainless Steel using HTS-SQUID

  • Park, D.G.;Kim, D.W.;Timofeev, V.P.;Hong, J.H.
    • Corrosion Science and Technology
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    • 제3권5호
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    • pp.222-225
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    • 2004
  • A portable RF HTS SQUID-based susceptometer was applied to the measurement of fatigue behavior for type 316L(N) stainless steel containing 0.04% to 0.15% nitrogen content. Strain-controlled low cycle fatigue (LCF) tests were conducted at RT and $600^{\circ}C$ in air an atmosphere, and the magnetic moments were measured after the fatigue test using HTS SQUID. The magnetic moment of an as-received sample is higher than that of a fatigued sample in all the temperature ranges irrespective of the nitrogen content. The fatigue life decreased with an increasing test temperature up to $500^{\circ}C$, but increased at $600^{\circ}C$. The change of the magnetic moments by LCF test is attributed to the stress induced micro defects.