• 대한기계학회논문집
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• 제14권1호
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• pp.103-111
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• 1990

본 연구에서는 성장하는 균열선단에서 열림변위의 임계증분에 대한 균열성장 조건에 기본을 두고 계산된 파단하중을 실험결과와 비교하여 균열성장저항을 특성 지 을수 있는 새로운 재료상수를 제안한 것이다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.40-45
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• 2000

Presented are the estimation of the probability distribution of fatigue crack growth life and reliability assessment of structures by simulating material resistance to fatigue crack growth along a crack path. The material resistance is treated as a Weibull stochastic process. A non-Gaussian stochastic fields simulation method proposed by Shimozuka, et al is applied with the statistical data obtained experimentally. Test results are obtained for $\Delta$K constant amplitude load in tension with stress ratio of R=0.2 and three specimen thicknesses of 6, 12 and 18mm. This simulation method is useful to estimate the probability distribution of fatigue crack growth life and the smallest life.

• 한국해양공학회지
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• 제14권4호
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• pp.73-78
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• 2000

Presented are the estimation of the probability distribution of fatigue crack growth life and reliability assessment of structures by simulating material resistance to fatigue crack growth along a crack path. The material resistance is treated as a Weibull stochastic process. A non-Gaussian stochastic fields simulation method proposed by shimozuka, et al is applied with the statistical data obtained experimentally. Test results are obtained for $\delta K$ constant amplitude load in tension with stress ratio of R=0.2 and three specimen thicknesses of 6,12 and 18mm. This simulation method is useful to estimate the probability distribution of fatigue crack growth life and the smallest life.

• 콘크리트학회논문집
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• 제18권4호
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• pp.553-558
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• 2006

본 연구에서는 배합강도 30MPa로 설계된 25-30-18 규격의 콘크리트 배합에 불소화합물 및 실리카로 구성된 불소-실리카 복합형 균열저감제(FS)를 시멘트 중량을 기준으로 0.5% 간격으로 2.0%까지 첨가한 후 슬럼프 경시 변화, 공기량 경시 변화 및 블리딩 등의 굳지 않은 콘크리트의 재료특성을 평가하였다. 또한, 콘크리트 수화온도 변화에 미치는 영향과 소성수축 및 건조수축의 저항성에 미치는 효과를 파악하였다. FS가 첨가된 콘크리트의 재료특성에서 슬럼프 및 공기량 경시 변화는 무첨가 콘크리트에 비해 큰 차이가 없었으나 블리딩과 수화온도는 저감되는 것으로 나타났다. 특히, 경화 전 후 소성수축 및 건조수축에 기인된 콘크리트의 수축균열 저항성이 FS를 $1.0{\sim}1.5%$의 첨가함으로써 크게 저감됨을 알 수 있었다.

• 한국해양공학회지
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• 제10권2호
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• pp.98-105
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• 1996

A method is proposed to evaluate the elastic-plastic fracture resistance curve only with load displacement records without the crack length measurement in CT specimen. This method is based on the idea that the effect of plastic deformation and the crack growth can be measured only by using a load-displacement record. If we know the reference-load curve representing the hardening of specimen, then the crack extension can be calculated by the elastic compliance determined from the load ratio. The results of this proposed method were compared to those of the elastic-plastic fracture resistance curve for the ASTM standard unloading compliance method. The experimental results for two kinds of ductile materials showed that the proposed method well simulates the material J-R curves. This method is currently applied for CT specimens. but it can be extended to the other specimen geometries.

• 연구논문집
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• 통권31호
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• pp.127-133
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• 2001

In chromium electrodeposition, crack is inevitably accompanied by chromium layer. Behavior of crack formation and crack density were different from the plating conditions such as current density, temperature, waveform of applied current and so on. And cracks have an influence on the corrosion resistance of chromium deposit, because corrosion occurs through the network of cracks between deposit and substrate. Therefore, many researches have been achieved in order to remove the cracks in chromium deposit. Formation of double layers, Cr/Cr and Ni/Cr were investigated to increase corrosion resistance of chromium deposit in this study. As pretreatment prior to outer chromium coating, acid pickling and current control method were examined. Cracks in cross-section of each sample were observed with SEM and CASS(Copper modified acetic acid salt spray) test was performed to evaluate corrosion resistance. It was found that corrosion resistance of Cr/Cr and Ni/Cr double layers were superior to Cr or Ni single layer from the results of CASS test.

• Elastomers and Composites
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• 제37권2호
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• pp.86-98
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• 2002

본 연구에서는 실리카/카본블랙 혼합사용과 카본블랙 단독 사용의 경우 상온 또는 고온에서의 인장강도(modulus) 및 인열저항성, 내cutting성, 내crack성을 비교 평가하였다. 실리카와 카본블랙의 함량비 및 단계배합 방법을 통해 NR 가황물을 제조하였으며, 충전제의 함량은 60phr로 고정하였고, semi-EV 가황시스템을 적용하여 실험을 실시하였다. 실리카의 분산은 25phr이하일 때 양호하였으며, 실리카/카본블랙의 함량비가 25/35인 경우 인열에너지, 내crack특성, 내cutting특성이 가장 우수하였다. 충전제로써 카본블랙 단독사용과 실리카/카본블랙(25/35) 혼합사용의 경우를 비교해 보면, 열화에 따른 modulus 및 인장강도, 인열에너지는 실리카/카본블랙(25/35)을 사용한 시편이 더 낮은 감소율을 나타내었다. Cutting특성에서는 카본블랙 단독 사용보다는 실리카/카본블랙(25/35) 혼합사용의 경우가 더 높은 cutting 저항성을 나타내었다. 내crack 특성 또한 실리카/카본블랙(25/35)을 혼합사용한 경우가 온도에 따른 더 높은 변형에너지 완화율(Gp)에도 불구하고 더 낮은 크랙성장속도를 나타내었다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1108-1114
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• 2001

The fatigue crack propagation behavior of the SA516-Grade 70 steel which is used for pressure vessels was experimentally examined under the condition of at room temperature, $150^{\circ}C$, $250^{\circ}C$ and $370^{\circ}C$ with stress ration of R=0.1 and 0.3. The fatigue crack propagation rate , da/dN, related with the stress intensity factor range, $\vartriangle$N, was influenced by the stress ration within the stable growth of fatigue crack(Region II) with an increase in $\vartriangle$N. The resistance to the fatigue crack growth at high temperature is higher in comparison with that at room temperature, and the resistance attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations revels that the differences of the fatigue crack growth characteristics between room and high temperatures are mainly explained by the crack and oxide-induced by high temperature.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.147-153
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• 2000

The fatigue crack propagation behavior of the SA516/70 steel which is used for pressure vessels was examined experimentally at room temperature, $150^{\circ}C$, $250^{\circ}C$ and $370^{\circ}C$ with stress ratio of R=0.1 and 0.3. The fatigue crack propagation rate da/dN related with the stress intensity factor range $\Omega\textrm{K}$ was influenced by the stress ratio within the stable growth of fatigue crack(Region II) with an increase in $\Omega\textrm{K}$. The resistance to the fatigue crack growth at high temperature is higher in comparison with that at room temperature, and the resistance attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and high temperatures are mainly explained by the crack closure and oxide-induced by high temperature.

• 한국해양공학회지
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• 제15권2호
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• pp.105-110
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• 2001

The fatigue crack propagation behavior of the SA516/70 steel which is used for pressure vessels was examined experimentally at room temperature, 150$^{\circ}C $, 250$^{\circ}C $ and 370$^{\circ}C $ with stress ratio of R=0.1 and 0.3. The fatigue crack propagation rate da/dN related with the stress intensity factor range $\Delta K$ was influenced by the stress ratio within the stable growth of fatigue crack(Region II) with an increase in $\Delta K$. The resistance to the fatigue crack growth at high temperature is higher in comparison with that at room temperature, and the resistance attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and high temperature are mainly explained by the crack closure and oxide-induced by high temperature.