• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.525-530
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• 2002

This study is peformed to propose the slab deck for the composite bridge with two girders. Considering the characteristics of the long span and the construction conditions in korea, a cast-in-place PSC deck was proposed for that bridge. To examine structural behaviors and safety of the proposed PSC deck, two real scale partitions of deck(12m$\times$3.2m) were tested under the fatigue loading. In the test, the failure mode and behaviors of each specimen, and the ultimate load carrying capacity of the two-girder-bridge deck were identified. Generally, the failure of concrete bridge deck is caused by the local punching shear stress resulting from the moving wheel load. Even though its ultimate flexural capacity is sufficiently larger than the demand, it could be failed by the punching shear fatigue. Therefore, the fatigue safety of the proposed PSC deck should be checked.

• 한국안전학회지
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• 제12권3호
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• pp.38-44
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• 1997

6063-T5 alloys are tested in laboratory air, water and 3% NaCl solution to investigate the effects of corrosive environment on the retardation behavior through single overload fatigue test. Also, the fatigue crack propagation and the crack closure behavior are studied. The results obtained in this experimental study are summarized as follows. 1) Behaviors of fatigue crack growth retardation are observed in water and 3% NaCl solution as they do in air. The number of delay cycles and the size of affected region by single overload decrease greatly in water and 3% NaCl compared with those in air. 2) In fractographic results, the overload marking by single overload appear remarkably in air, but indistinctly in water and 3% NaCl solution. 3) The effect of crack closure on crack propagation is most remarkable in the beginning of crack propagation. With crack propagation, the crack closure level and its effect decrease greatly.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.505-506
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• 2009

이 논문은 보수 보강 공법으로 쓰이고 있는 FRP bar와 GSP 매입공법의 피로거동에 대한 연구이다. 실험에서 응력비 R는 0.1이고 피로하중 주파수는 1.5Hz이다. 피로실험 결과, S-N 곡선에서 GFRP bar와 GSP 보강보의 피로강도는 각각 정적강도의 58%, 52% 수준임을 얻었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.558-567
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• 2003

The catenary wires are damaged by periodic running of train as well as repeated stress. The wires are also degraded by atmosphere corrosion at fields. Corrosion of wires increased surface roughness and deteriorated mechanical properties by providing fatigue crack initiation sited resulting in a bad effect on service life of the wires. Fatigue test of catenary wires performed to estimate service lifetime. Also, simulation to analyze stress on catenary wires was conducted through modelling the finite elements for dynamic behaviors of wires. Fatigue life of catenary wires was estimated with fatigue and simulation tests.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.87-92
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• 2001

In this paper, high strength pressure vessel steels having the same chemical compositions were manufactured by the two different steel-making processes, such as vacuum degassing(VD) and electro-slag remelting(ESR) methods. After the steel-making process, they were normalized at $955^{\circ}C$, quenched at $843^{\circ}C$, and finally tempered at $550^{\circ}C$ or $450^{\circ}C$, resulting in tempered martensitic microstructures with different yielding strengths depending on the tempering conditions. Low-cycle fatigue(LCF) tests, fatigue crack growth rate(FCGR) tests, and fracture toughness tests were performed to investigate the fatigue and fracture behaviors of the pressure vessel steels. In contrast to very similar monotonic, LCF, and FCGR behaviors between VD and ESR steels, a quite difference was noticed in the fracture toughness. Fracture toughness of ESR steel was higher than that of VD steel, being attributed to the removal of impurities in steel-making process.

• Structural Engineering and Mechanics
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• 제75권1호
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• pp.19-32
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• 2020

Due to repetitive traffic loadings and environmental attacks, reinforced concrete (RC) bridge deck slabs are suffering from severe degradation, which makes structural repairing an urgency. In this study, the fatigue performance of an RC bridge deck repairing technique using ultra-high performance fiber reinforcement concrete (UHPFRC) overlay is assessed experimentally with a wheel-type loading set-up as well as analytically based on finite element method (FEM) using a crack bridging degradation concept. In both approaches, an original RC slab is firstly preloaded to achieve a partly damaged RC slab which is then repaired with UHPFRC overlay and reloaded. The results indicate that the developed analytical method can predict the experimental fatigue behaviors including displacement evolutions and crack patterns reasonably well. In addition, as the shear stress in the concrete/UHPFRC interface stays relatively low over the calculations, this interface can be simply simulated as perfect. Moreover, superior to the experiments, the numerical method provides fatigue behaviors of not only the repaired but also the unrepaired RC slabs. Due to the high strengths and cracking resistance of UHPFRC, the repaired slab exhibited a decelerated deterioration rate and an extended fatigue life compared with the unrepaired slab. Therefore, the proposed repairing scheme can afford significant strengthen effects and act as a reference for future practices and engineering applications.

• 한국기계가공학회지
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• 제11권4호
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• pp.82-89
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• 2012

In order to clarify the effect of overload on crack growth behaviors, fatigue tests for overload were carried out for round plain specimens of SM45C steel. In the experiment, typical semi-elliptical crack shape was found and further crack growth behaviors were tested. Using three types of single overload fatigue tests, Crack growth retardation phenomenon were examined. The growth rate of surface crack(da/dN) during retardation period was analyzed in terms of ${\Delta}K$ and ${\Delta}K_{eff}$. On the growth rate of surface crack analyzed by ${\Delta}K$, the dependence of overload stress levels appears. However, on the growth rate by ${\Delta}K_{eff}$ obtained by Willenborg analysis, there is a liner relationship between da/dN and ${\Delta}K_{eff}$ with narrow scatter band.

• 대한기계학회논문집A
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• 제21권1호
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• pp.173-179
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• 1997

The high temperature fatigue tests were performed using the specimens taken from Cr-Mo-V steel, widely used as thermal power plant turbine materials for examination fatigue behavior of materials in power plants which have been operated for long periods. The fatigue tests at high temperature were performed at the various temperature and applied stress. The results obtained are summarized as follows : The fatigue crack length increases and the fatigue life decreases with temperature and applied stress according to the same number of stress cycle. The fatigue crack propagation and the fatigue life were much influenced by temperature and applied stress.

• 대한기계학회논문집
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• 제8권3호
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• pp.195-200
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• 1984

본 연구에서는 SUS 304강의 상온하의 평골재 표면에 발생. 성장하는 미소표면 피로균열의 거동을 파괴역학적 관점과 수법으로 정량적으로 조사하려는 연구의 일환 이다.

• Corrosion Science and Technology
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• 제11권4호
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• pp.120-128
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• 2012

The fatigue crack growth behaviors of SA508 Gr.3 Cl.2 low alloy steel in high temperature water environment were investigated. Overall, weld metal showed similar crack growth rate as that of base metal. At 0.01 Hz, fatigue crack growth rate (FCGR) was higher than that in air while the difference was smaller at 0.1 Hz. Also, FCGR showed ${\Delta}K$ dependency at 0.1 Hz only, indicating that the environmental effect was much greater at slower loading frequency of 0.01 Hz. FCGR of SA508 Gr.3 Cl.2 low alloy steel was compatible to or smaller than the ASME Sec. XI fatigue reference curves in high temperature water environment.