• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2465-2471
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• 2012

For the steel structures those are used in harsh sea environments, corrosion fatigue is a challenging issue in connection with design life. In this research, in order to investigate the influence of cathodic overprotection on the corrosion fatigue crack propagation behavior, corrosion fatigue crack propagation test under the condition of -950mV vs SCE was conducted by using of high tensile TMCP steel plate and the relationships between da/dN-${\Delta}K$ were obtained. At this test, when ${\Delta}K$ is low, the crack propagation rates were accelerated compared to those of seawater condition, however, when ${\Delta}K$ is high, the crack propagation rates were lower than those of seawater condition. As the cause for the acceleration and deceleration of corrosion fatigue crack propagation rates under the condition of cathodic overprotection, the role of hydrogen and calcareous deposits are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2374-2385
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• 1994

SiCw/Al composite material is especially attractive because of their superior specific strength, specific stiffness, corrosion fatigue resistance, creep resistance, and wear resistance compared with the corresponding wrought Al alloy. In this study, Fatigue crack growth behavior and fatigue crack path morphology(FCPM) of SiC whisker reinforced Al 6061 alloy with 25% SiC volume fraction and Al 6061 allay were performed. Result of the fatigue crack growth test sgiwed that fatigue crack growth rate of SiCw/Al 6061 composite was slower than that of Al 6061 matrix therefore it was confirmed that Sic whisker have a excellent fatigue resistance. And Al 6061 matrix had only FCPM perpendicular to loading direction. On the other hand SiCw/Al 6061 composite had three types in fatigue crack path morphology. First type is that both sides FCPM of artificial notch are perpendicular to loading direction. Second type is that a FCPM in artifical notch has slant angle to loading direction and the other side FCPM is perpendicular to loading direction. Third type is that both sides FCPM of notch have slant angle to loading direction. It was considered that this kinds of phenomena were due to non-uniform distribution of SiC whisker and confirmed by SEM observation for fracture mechanism study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.3
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• pp.53-62
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• 1986

For the research on the fatigue fracture behavior in the welded joints of steel structures, base metal specimens and welded ones were selected, and the direct fatigue tests were carried out. Thereafter, fatigue-life (S-N) curves, plastic strain-number of cycles (${\varepsilon}_p$-N) curve, the extrapolated fatigue-life (${\varepsilon}_p$-$N_c$) curve, and da/dN-${\Delta}K$ curves were plotted. By these results the followings were obtained. It was shown that the ratio of fatigue strength at $2{\times}10^6$ cycles of the welded specimen to that of the base metal one was 0.6, and that 0.72 for the base metal and 0.65 for the welded one were the ratio of fatigue strength at $2{\times}10^6$ cycles to yielding stress. The S-N curve for the welded specimen was separated into two sections, the low gradient section and the steep section. As this result, it was shown that the more stress became to reduce, the more the reduction of fatigue strength became to be great. It was shown that fatigue strength at $2{\times}10^6$ cycles from this case was about 83 % of that from the S-N curve plotted with one section. It was thought that the reason was that weld flaw acted greatly on the fatigue strength within the low stress range. It was shown that at the instart of crack initiation plastic strain increased abrupt1y in the case of the welded specimen more than the case of the base metal specimen, and increased abruptly in the upper stress range in both cases. It was shown that the experimental constant ${\alpha}$, 0.42, in the base metal nearly accorded with Manson-Coffin's result, but this made a great difference with the case in the welded specimen. It was thought that it was due to the abrupt change of plastic strain and the influence of weld flaw.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.46-51
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• 2007

In this study, test results for fatigue crack propagation of Al-2024-T3511 are presented considering corrosion effects, and fatigue lifes are compared for the cases of corrosion and non-corrosion. Higher corrosion environments show lower fatigue life and faster crack growth. To predict the corrosion fatigue life, a corrosion factor concept is newly introduced and applied in Paris' law. The predicted results show good agreement with experimental data and this corrosion fatigue model can be successfully used for the prediction of fatigue life of aluminum structure with corrosion effects.