Abstract
It is clear that detection of fatigue crack initiation in complex welded structures like hulls is quite difficult, and that the crack length at recognition is mostly long compared to that in mechanical parts. From these facts, not only stress reduction at critical area by design improvement, but also newly developed steels excellent for fatigue crack propagation resistance are desirable for structural integrity. Newly developed structural steel FCA, in which fatigue crack propagation resistance was controlled by metallic microstructures, was introduced in the part one within a series of our research. Various fatigue properties of FCA in air and in synthetic sea water were reported in the part two. As the continuous research after these two papers, fatigue properties of various welded joints with FCA are compared with those with conventional steel. From these experimental results, it can be clarified that the fatigue life extension effect by FCA is observed also in welded joint specimens and welded structural models as the same as FAC itself.
