表層超細粒鋼板の海水中疲労強度とその評価(その3)

概要

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In this paper, observations on the initiating and propagating behaviors of a corrosion pit and a corrosion fatigue crack in artificial sea water were made, in order to grasp more clearly the difference of fatigue strength in artificial sea water between surface layer and mid-section of a SUF plate. For observations and some considerations, the specimens, which were cut off from surface layer and mid-section of the SUF plate respectively, were used. As a result of quantitative considerations described above, the following conclusions were obtained: (1) It becomes clear quantitatively that a corrosion fatigue crack is initiated rather hard on the surface layer with ultra fine grain microstructure compared with on the mid-section with the microstructure similar to that of conventional TMCP steel plate. That is, under the almost same stress range (Δσ), the sizes (length, depth, width) and the stress intensity factor (ΔK) of a corrosion pit and a corrosion fatigue crack when a corrosion fatigue crack starts propagating on surface layer are larger than those on mid-section. (2) The corrosion fatigue crack initiation life (Nc) of surface layer is about 48 times longer than that of mid-section when a stress range (Δδ) is 36〜37kgf/mm^2.
社団法人日本船舶海洋工学会の論文
1999-09-04