PART-THROUGH SURFACE FATIGUE CRACK GROWTH CHARACTERISTICS OF HIGH-TENSILE STRENGTH STEELS IN SYNTHETIC SEA WATER.

Part-through surface fatigue crack growth rates of high-tensile strength steels have been measured in ASTM synthetic sea water at free corrosion potential and under a cathodic potential. The aspect ratio in synthetic sea water at free corrosion potential was larger than that in air; while under a cathodic potential it was almost fixed and the same as that in air. At free corrosion potential at R equals 0. 1, the crack growth rate to inside da/dN was firstly faster than the one along surface dc/dN because the inside is under a plane-strain condition, and the O//2 concentration is lower than that at the surface. Afterwards, the da/dN and dc/dN were entirely the same as that of a through-crack type specimen, both at free corrosion and under a cathodic potential. Under a cathodic potential, the threshold values were remarkably high because the Ca and Mg deposits-induced wedge effect was so conspicuous.