Fatigue Crack Growth in Three 180-Ksi Yield Strength Steels in Air and in Salt-Water Environments

摘要

Fatigue crack propagation studies were conducted on three high-strength structural steels; 9Ni-4Co-0.25C, 12Ni maraging, and 18Ni maraging. Each of the steels was heat treated to a yield strength of 180 ksi. Tests were performed in two environments, a 'dry' environment consisting of ambient room air and a 'wet' environment consisting of 3.5-percent-NaCl salt water. Relationships for fatigue crack growth rates as a function of the fracture mechanics, stress-intensity factor (K) are developed for each steel, in both environments. The engineering significance of these relationships are then presented in terms of stress levels and flaw sizes relevant to the steels under investigation. (Author)