• 제목/요약/키워드: Static and fatigue behavior

검색결과 179건 처리시간 0.024초

SUS 304 강의 크리프 온도역에 있어서 피로균열성장거동에 관한 연구 (A Study on Fatigue Crack Growth Behavior at a Creep Temperature Region in SUS 304 Stainless Steel)

  • 주원식;오세욱;조석수
    • 대한기계학회논문집
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    • 제18권3호
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    • pp.548-554
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    • 1994
  • The high temperature fatigue crack growth behavior of SUS 304 stainless steel at $550^{\circ}C$ and $650^{\circ}C$ was investigated under various kinds of stress ratio and frequency in sinusoidal waveform on the basis of the non-linear fracture mechanics. The result arranging crack growth rate by modified J-integral J' showed influence of stress ratio and frequency. All the data obtained under the test at $550^{\circ}C$ were plotted within data band of da/dN-${\triangle}J_f$ relationship for cycle-dependent crack growth. On the basis of static creep and cycle-dependent data band; both time- and cycle-dependent crack growth behavior was observed under loading conditions at $650^{\circ}C$, but cycle-dependent crack growth behavior predominantly appeared and time-dependent crack growth behaviour was little observed under loading conditions at $550^{\circ}C$. Fractographic examinations for fracture surface indicated that the fracture mode was generally transgranular. The stripes were found on fracture surface and each stripe was accompanied by a crack tip blunting and an abrupt increase in the load-point displacement. The $J'_{an}$ had a validity in case of $650^{\circ}C, but scarcely had it in case of $550^{\circ}C$.

베어링-축계의 부정정계 해석 및 볼베어링의 거동예측 (Analysis of Statically Indeterminate Bearing-Shaft System and Prediction of the Behavior of Ball Bearing)

  • 김완두;한동철
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1993년도 제18회 학술대회 초록집
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    • pp.70-76
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    • 1993
  • From the analysis of shaft-bearing indeterminate system, moment and misalingment angle which was generated in bearing were determined. And the influence of span length between bearings on the fatigue life was established. The equation to estimate the cage rotational speed was proposed, and this equation was verified by the measuring of cage speed and shaft speed. And accoding to quasi-static analysis, the spinning speed of ball was determined.

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FRP 긴장재를 이용한 프리스트레스트 콘크리트 보의 피로 거동 (Fatigue Behavior of Prestressed Concrete Beams Using FRP Tendons)

  • 김경남;박상렬;김창훈
    • 콘크리트학회논문집
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    • 제23권2호
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    • pp.135-144
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    • 2011
  • 최근 PS 강연선의 대체재로서 높은 인장강도와 훌륭한 내부식을 가진 FRP(fiber rienforced polymer)를 이용한 조사가 활발히 진행되어지고 있다. 따라서, 이 연구는 FRP 긴장재를 이용한 프리스트레스트 콘크리트 보를 제작하여 반복 하중에 따른 피로거동의 특성을 분석함으로써 프리스트레스트 콘크리트 보의 안전성을 평가하고자 하였다. 또한 기존 PS 강연선을 이용한 프리스트레스트 콘크리트 보를 제작하여 피로 성능을 비교하였다. 반복 하중은 정적 실험을 통해서 얻은 극한 하중의 40%를 최소 하중으로 일정하게 고정하고 최대 하중은 극한 하중의 60%, 70%, 80%로 결정하였다. 반복 하중은 4점 재하방식으로 sine파를 이용한 1~3 Hz의 속도 재하하였다. 피로한계는 100만회로 하였다. 40~60% 범위의 시험체는 100만회까지 피로 파괴가 나타나지 않았지만, 반복 횟수가 증가함에 따라 콘크리트와 긴장재 사이의 부착력이 저하되었고, 수평방향의 균열이 나타났다. FRP 긴장재를 이용한 프리스트레스트 콘크리트 보의 피로 실험 결과 사용 하중 상태에서의 반복 하중에 대해서 안전한 것으로 나타났다. 피로한계 100만회에 대한 피로 강도는 FRP 긴장재를 이용한 프리스트레스트 콘크리트 보의 경우 69.2%, PS 강연선을 이용한 프리스트레스트 콘크리트 보는 59.8%에 해당함을 알 수 있었다.

Numerical modeling for cyclic crack bridging behavior of fiber reinforced cementitious composites

  • Shin, Kyung-Joon;Lee, Kwang-Myong;Chang, Sung-Pil
    • Structural Engineering and Mechanics
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    • 제30권2호
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    • pp.147-164
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    • 2008
  • Recently, many researches have been done to examine the behavior of fiber reinforced concrete (FRC) subjected to the static loading. However, a few studies have been devoted to cyclic behaviors of FRC. A main objective of this paper is to investigate the cyclic behavior of FRC through theoretical method. A new cyclic bridging model was proposed for the analysis of fiber reinforced cementitious composites under cyclic loading. In the model, non-uniform degradation of interfacial bonding under cyclic tension was considered. Fatigue test results for FRC were numerically simulated using proposed models and the proposed model is achieving better agreement than the previous model. Consequently, the model can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

Lifetime seismic performance assessment of high-rise steel-concrete composite frame with buckling-restrained braces under wind-induced fatigue

  • Liu, Yang;Li, Hong-Nan;Li, Chao;Dong, Tian-Ze
    • Structural Engineering and Mechanics
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    • 제77권2호
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    • pp.197-215
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    • 2021
  • Under a severe environment of multiple hazards such as earthquakes and winds, the life-cycle performance of engineering structures may inevitably be deteriorated due to the fatigue effect caused by long-term exposure to wind loads, which would further increase the structural vulnerability to earthquakes. This paper presents a framework for evaluating the lifetime structural seismic performance under the effect of wind-induced fatigue considering different sources of uncertainties. The seismic behavior of a high-rise steel-concrete composite frame with buckling-restrained braces (FBRB) during its service life is systematically investigated using the proposed approach. Recorded field data for the wind hazard of Fuzhou, Fujian Province of China from Jan. 1, 1980 to Mar. 31, 2019 is collected, based on which the distribution of wind velocity is constructed by the Gumbel model after comparisons. The OpenSees platform is employed to establish the numerical model of the FBRB and conduct subsequent numerical computations. Allowed for the uncertainties caused by the wind generation and structural modeling, the final annual fatigue damage takes the average of 50 groups of simulations. The lifetime structural performance assessments, including static pushover analyses, nonlinear dynamic time history analyses and fragility analyses, are conducted on the time-dependent finite element (FE) models which are modified in lines with the material deterioration models. The results indicate that the structural performance tends to degrade over time under the effect of fatigue, while the influencing degree of fatigue varies with the duration time of fatigue process and seismic intensity. The impact of wind-induced fatigue on structural responses and fragilities are explicitly quantified and discussed in details.

Fatigue performance and life prediction methods research on steel tube-welded hollow spherical joint

  • Guo, Qi;Xing, Ying;Lei, Honggang;Jiao, Jingfeng;Chen, Qingwei
    • Steel and Composite Structures
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    • 제36권1호
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    • pp.75-86
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    • 2020
  • The grid structures with welded hollow spherical joint (WHSJ) have gained increasing popularity for use in industrial buildings with suspended cranes, and usually welded with steel tube (ST). The fatigue performance of steel tube-welded hollow spherical joint (ST-WHSJ) is however not yet well characterized, and there is little research on fatigue life prediction methods of ST-WHSJ. In this study, based on previous fatigue tests, three series of specimen fatigue data with different design parameters and stress ratios were compared, and two fatigue failure modes were revealed: failure at the weld toe of the ST and the WHSJ respectively. Then, S-N curves of nominal stress were uniformed. Furthermore, a finite element model (FEM) was validated by static test, and was introduced to assess fatigue behavior with the hot spot stress method (HSSM) and the effective notch stress method (ENSM). Both methods could provide conservative predictions, and these two methods had similar results. However, ENSM, especially when using von Mises stress, had a better fit for the series with a non- positive stress ratio. After including the welding residual stress and mean stress, analyses with the local stress method (LSM) and the critical distance method (CDM, including point method and line method) were carried out. It could be seen that the point method of CDM led to more accurate predictions than LSM, and was recommended for series with positive stress ratios.

용입부족을 가진 횡방향 맞대기 용접부의 피로특성에 관한 연구 (A Study on the Fatigue Characteristics in Butt-Welded Joints with Incomplete Penetration)

  • 장동일;경갑수;홍성욱
    • 한국강구조학회 논문집
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    • 제10권3호통권36호
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    • pp.497-508
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    • 1998
  • 본 연구에서는 평면결함의 일종인 용입부족의 크기가 맞대기 용접부의 피로 특성에 미치는 영향을 정량적으로 규명하였다. 정적실험 결과 비드를 삭제하지 않은 맞대기 용접부의 인장강도와 항복강도는 용입부족 크기에 관계없이 일정하였다. 또한 피로실험 결과 완전용입된 맞대기 용접부의 피로강도는 국내 외의 시방서에서 규정하고 있는 피로 등급을 모두 만족하며, 용입부족 크기에 따른 피로강도의 저하는 용입부족 크기가 증가함에 따라 피로강도가 급격하게 감소하였다. 파단형태에서 완전용입 시험체와 용입부족 시험체의 파단형태가 서로 다른 형식을 취하고 있음을 알 수 있었는데 이는 용접지단부와 용접루트부의 기하학적 형상에 따른 응력집중계수의 변화에 기인하는 것을 유한요소해석에서 확인하였다. 따라서 강구조물에 대한 용접제작시 발생할 수 있는 용접결함 중 평면결함의 일종인 용입부족은 반드시 피해야만 강구조물의 공용수명을 충분히 확보할 수 있을 것이다.

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고장력볼트 T-인장이음의 피로거동에 관한 실험적 연구 (An Experimental Study on the Fatigue Behavior of T-Type Tension Joints with High Tension Bolt)

  • 이승용;최준혁
    • 한국강구조학회 논문집
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    • 제28권6호
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    • pp.459-465
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    • 2016
  • 본 연구에서는 인장이음에 대한 반복하중의 영향을 파악하기 위하여 단순 인장이음을 대상으로 피로시험을 수행하였다. 인장이음의 볼트체결에 따른 축력과 작용하중에 의한 축력의 변화를 측정하였고 반복하중에 의한 볼트의 축력과 파괴양상, 이음의 피로강도를 조사하였다. 인장이음의 구조 상세 변수는 플랜지 두께와 고장력 볼트의 직경으로서 이들의 조합에 따라 볼트와 연결부의 강성이 달라지도록 하였다. 피로시험결과, 반복하중을 받는 인장이음의 파괴모드는 EC3에서 제시하고 있는 정적 파괴모드별 극한하중을 이용하여 평가될 수 있었다. 인장이음의 피로강도는 지레작용을 고려하지 않은 EC3(36)의 피로강도보다 상당히 안전측의 결과로 나타났다. 그러나, 지레작용에 의한 부가축력은 볼트 축력의 증가를 일으키기 때문에 피로강도에 대한 신중한 평가가 필요하다.

강섬유보강 콘크리트의 휨 피로거동에 관한 연구 (Flexural Fatigue Bechavior of Steel Fiber Reinforced Concrete Structures)

  • 장동일;채원규;손영현
    • 콘크리트학회지
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    • 제4권1호
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    • pp.81-87
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    • 1992
  • 본 논문에서는 강섬유 혼입량과 강섬유 형상비에 대한 강섬유보강콘크리트의 휨 피로거동을 분석하기 위하여 일련의 강섬유보강콘크리트 시험체에 대하여 피로실험을 수행하였다. 피로실험은 3점 휨 실험법으로 실시하였으며, 실험시 각 시험체의 하중반복회수에 대한 중앙처짐과 피로파괴시의 반복회수를 조사하였다. 이들 실험 결과를 토대로 반복회수에 대한 강섬유보강콘크리트의 중앙처짐, 비탄성변형에너지 및 탄성변형형에너지등을 비교 분석하였으며, 강섬유보강콘크리트의 S-N선도를 작도하였다. 연구결과, 강섬유 혼입량이 클수록 영구변형에 손실되는 에너지가 크게 감소하고, 균열 확대에 소모되는 에너지가 증가하였으며, 동일한 강섬유 혼입량을 갖는 강섬유콘크리트의 경우 강섬유 형상비가 클수록 탄성변형에너지는 작았다. 아울러 본 피로실험 결과를 회귀분석하여 구한 S-N선도에 의하면 강섬유 혼입량이 1.0%인 강섬유보강 콘크리트의 반복회수 200만회에 대한 피로초기균열 발생시의 정적강도의 약 70%로 나타났다.

Effects of geometric shape of LWSCR (lazy-wave steel catenary riser) on its global performance and structural behavior

  • Kim, Seungjun;Kim, Moo-Hyun
    • Ocean Systems Engineering
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    • 제8권3호
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    • pp.247-279
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    • 2018
  • This study aims to investigate the behavioral characteristics of the LWSCR (lazy-wave steel catenary riser) for a turret-moored FPSO (Floating Production Storage Offloading) by using fully-coupled hull-mooring-riser dynamic simulation program in time domain. In particular, the effects of initial geometric profile on the global performance and structural behavior are investigated in depth to have an insight for optimal design. In this regard, a systematic parametric study with varying the initial curvature of sag and arch bend and initial position of touch down point (TDP) is conducted for 100-yr wind-wave-current (WWC) hurricane condition. The FPSO motions, riser dynamics, constituent structural stress results, accumulated fatigue damage of the LWSCR are presented and analyzed to draw a general trend of the relationship between the LWSCR geometric parameters and the resulting dynamic/structural performance. According to this study, the initial curvature of the sag and arch bend plays an important role in absorbing transferred platform motions, while the position of TDP mainly affects the change of static-stress level.