抄録
In order to study life prediction method of structural material for sea environment use, the field testing facility to measure the fatigue crack growth rate of the materials due to sea wave was developed. The tests of fatigue crack growth rate measurements using 3.5% Ni-Cr-Mo-V structural steels were performed in cathodic protection and free corrosion environments.
The field test data were analized using the rainflow method and equivalent load (Peq) equation. When the yeild strength and the stress ratio increase, the fatigue crack growth rate increases. The fatigue crack growth rate of field test results was little different from indoor test results obtained using ASTM sea water. This difference may be caused by the change of stress ratio and frequency conditions. The crack growth rate of indoor test using field test conditions coincided well with the field test results. In observation of fracture surface of the specimens, fatigue crack containing intergranular fracture was observed. The higher yield strength material showed larger amount of intergranular fracture.
This study demonstrates that the fatigue crack growth behavior in actual sea field environment can be obtained using indoor test data.
