CRACK CLOSURE EFFECTS ON FATIGUE-CRACK GROWTH THRESHOLDS AND REMAINING LIFE IN AN HSLA STEEL

The effects of crack closure on the near-threshold corrosion fatigue c rack growth behavior of Mil S-24645 HSLA steel and its weld metal have been investigated in air, ASTM seawater at the free corrosion potenti al, and ASTM seawater at -0.8V and -1.0V (SCE) using frequencies of 10 , 2, and 0.2 Hz, and a stress ratio, R = 0.1. Remaining life, in the p resence and absence of crack closure, has been estimated as a function of applied stress range for a structure containing a 3-nm-deep surfac e semi-elliptical flaw.