• Journal of the KSME
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• v.28 no.4
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• pp.313-321
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• 1988

어떤 구조물이 반복하중을 받으면 피로파괴를 일으킨다. 만일 이 구조물이 부식환경 속에 앗 으면 불활성 분위기나 공기 중에서 보다 빨리 파괴에 이르게 된다. 이러한 현상을 흔히 부식 피로라고 한다. 부식피로에 크게 영향을 미치는 변수들을 대략 기계적 변수, 금속학적 변수, 환경 변수로서, 기계적 변수에는 최대응력 확대계수, 응력확대계수범위, 응력비, 반복하중 주파수, 반복하중파형, 응력상태, 잔류응력, 균열의 크기 및 모양 등이 있으며 금속학적 변수로는 합금 조성, 합금원소와 불순물의 분포, 미세조직과 결정구조, 열처리, 소성가공, 집합조직 등이며 환 경변수에는 온도, 환경의 형태(기체, 액체), 부식성분의 분압 또는 농도, 전기화학적 전위, pH, 수용성 환경의 점성, 피복, 부식억제제 등이 있다. 이와 같이 부식환경 속에 있는 구조물의 파 손을 이해하기 위하여는 응력부식과 부식피로를 공부하여야 한다. 이 현상은 매우 복잡한 문 제이기 때문에 아직도 완전히 이해되지 않은 상태이고 따라서 중요한 연구대상이 되고 있다. 여기서는 응력부식과 부식피로의 파괴역학적인 측면을 소개하고자 한다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.359-364
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• 1996

'93.4월에 고리원자력 4호기 운전중(원자로 출력 100%, 발전기 출력 975MWe) 주증기 차단밸브 (MSIV)의 닫힘으로 인해 발전소가 정지되었다. 밸브분해 점검결과 밸브스템이 Back Seat Ring 조립부위 Notch 부위에서 Steam Flow와 평행한 방향으로 절단되어, 밸브스템의 손상원인을 규명하기 위한 본 연구에서는 피로해석절차도에 따라 S-N 곡선에 근거하여 피로해석을 수행하였다. 피로해석결과 밸브스템의 초기균열 생성원인은 Stem Notch 부위의 제작결함과 발전소 정지시 밸브를 급속히 닫을 때 작용하는 충격하중등에 의해 발생된 것으로 추정되며 인장평균응력과 관내 유체의 진동하중의 변동응력이 조합하여 피로균열을 가속시켜 파손을 일으킨 것으로 사교된다.

• Magazine of the Korea Concrete Institute
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• v.9 no.3
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• pp.137-147
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• 1997

Interface shear strength of' concrete under static loading and deterioratiion of interface strength by fatigue loading in shear were experimentally investigated using composite beam test specimens. Thirteen beams were constructed. Five composite beams were tested statically until interface delaminations were observed in the static tests. Seven composite beam and one monolithically cast beam were subjected to two to three million cycles of fatigue load. Test variables were interface roughness, interface shear reinforcement, and presence of interface bond. The average interface shear strength of the composite beams with bonded-rough interface was 6, 060 kPa. No interface delamination was observed after cycling for the composite beams with bonded - rough interface and interface bond was not influenced by repeated application of the shear stress of 2.000 kPa(about 1/3 of the static interface shear strength). Smooth interface and unbonded-rough interface with shear reinforcement deteriorated under repeated shear loading.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.431-439
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• 2010

In this paper, dynamic behavior of steel fiber reinforced concrete(SFRC) by experimental method is discussed. Because of its improved ability to dissipate energy, impact resistance and fatigue behavior, SFRC has a better dynamic behavior than that of plain concrete. Dynamic behavior is influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and the stress level. Impact resistance and fatigue behavior in the SFRC has been evaluated from dynamic experimental test data at various levels of cracked states in the elements.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.193-204
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• 1997

In order to quantify the relationships of the important physical factors relating failure to strong earthquake loading, the plastic fatigue problems for structural components under repeated loading were reviewed first. A new concept of very low cycle fatigue failure for structural components under severe cyclic excitations as in strong earthquakes was represented. Also, an experimental study was made of the very low cycle fatigue failure of structural steel elements. It was attempted to realize the ultimate failure in the course of loading repetitions of the order of several to twenty. The test specimen had a form of rectangular plate, representing a thin-plated element in a steel member as wide-flange cross section. It was subjected to uniaxial loading repeatedly, until complete failure takes place after undergoing inelastic buckling, plastic elongation and/or their combination. It was seen as a result that the state of the ultimate failure is closely related to the maximum strain at the extreme fiber in the cross section.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.83-92
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• 1987

Fatigue fracture of reinforced concrete structures are characterized by considerably larger strains and microcracking as compared to fracture of R.C. structures under static loading. The strain of stirrup is increased suddenly by the occuring of inclined crack and the average strain ${\epsilon}_{\omega}$ of all stirrups in a structure at maximum load increase approximately in proportion to log N. The structures critical in longitudinal reinforcement seemed to have an endurance limit of 60~70 percent of static ultimate strengths for 1,000,000 cycles. In this test, the average fatigue strength at 1,000,000 cycles for all structures tested was approximately 65 percent of the static ultimate strength.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2000.06a
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• pp.215-222
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• 2000

반복하중을 받는 대부분의 토목구조물은 정적하중보다 훨씬 낮은 하중에서 파괴가 발생하는 경우가 있는데 이러한 현상을 피로라고 하며, 특히 강교량을 구성하는 부재중에서 2차 부재에 해당되는 덮개판, 수평보강재, 수직보강재, 거셋트 등의 용접부에서는 여러 원인으로 인해서 피로손상이 발생하게 되어 결국에는 구조물의 성능에 크게 영향을 미치게 된다. (중략)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.594-599
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• 2011

In this paper, the effect of the boundary conditions on the reliability and the cumulative distribution characteristics of the fatigue failure life is analyzed in a magnesium alloy AZ31. The boundary conditions are specimen thickness, stress ratio, and maximum fatigue load. The statistical data of the fatigue failure life are obtained by fatigue crack propagation tests under the detail conditions for each boundary condition. The 3-parameter Weibull distribution is used to analyze a statistical characteristics of the fatigue failure life in magnesium alloy AZ31. It is found that the statistical fatigue failure life is long in the case of a thicker specimen, a larger stress ratio, and a smaller maximum fatigue load. Under the opposite cases, the reliability on the fatigue failure life is rapidly dropped.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.63-69
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• 2015

The primary aim of this paper is to evaluate the probabilistic fatigue crack propagation models using the residual of a random variable and to present the probabilistic model fit for the probabilistic fatigue crack growth behavior in Mg-Al-Zn alloys under maximum load conditions. The models used in this study were prepared by applying a random variable to empirical fatigue crack propagation models such as the Paris-Erdogan model, Walker model, Forman model, and modified Forman model. It was verified that the good models for describing the stochastic variation of the fatigue crack propagation behavior in Mg-Al-Zn alloys under maximum load conditions were the 'probabilistic Paris-Erdogan model' and 'probabilistic Walker model'. The influence of the maximum load conditions on the stochastic variation of fatigue crack growth is also considered.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.459-465
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• 2016

In this paper, it was performed the fatigue test to examine the effect of cyclic loading for the simple T-joint. Axial force of bolt by clamping and the change of the force by applied load were measured in the joint. And the bolt force, the failure mode and the fatigue strength under cyclic loading were investigated. The parameters of the tension joint were set to be the flange thickness and the diameter of bolt to a different stiffness of the joint in response to the combination. From the fatigue test, failure mode of tensile joints under cyclic loading could be evaluated using a static ultimate load of the specific failure mode in EC3. The fatigue strength of the tension joints was considerably higher than the fatigue strength of the EC3(36) that does not consider a lever action. However, the additional axial force by lever action occurs to an increase in the axial force of the bolt it requires a careful evaluation of the fatigue strength.