Abstract
Corrosion fatigue crack initiation behavior was investigated in high-tensile-strength steels in synthetic seawater. The materials tested were the following high-tensile-strength steels : 50 kgf/mm2 HT 50, HT 50-TMCP and HT 50 weldment, and 80 kgf/mm2 HT 80. The rotating bending and plate bending fatigue tests were performed at a frequency of 0.17 Hz with a load ratio of -1. Corrosion fatigue strengths of these steels were monotonously decreased with increasing load cycles in log-log plots. The strengths of the base plate and weldment of HT 50 were similar. Corrosion fatigue cracks of these steels were initiated when a pit depth exceeded a threshold value. ΔK values calculated by assuming pits containing a crack as sharp cracks remained almost constant, in spite of the pit growth with increasing load cycles, and the mechanical condition dominating crack initiation of these steels was determined by the average stress intensity factor range at the deepest point of pit, ΔKCF.
