Load Ratio and Environmental Effects on Fatigue Crack Growth Rates for Several Ship Steels

摘要

Fatigue crack growth rate tests were conducted on HY-100, high tensile steel (HS) and medium carbon ship steels. Tests were conducted in air at 5 Hz and in 3.5 percent NaCl salt water under freely corroding conditions at 0.5 Hz. Load ratios of 0.10, 0.67 and 0.80 were investigated in both environments. For data gathered in air, crack growth rates (da/dN) were insensitive to stress ratio and the data conformed to a Paris power law relationship between da/dN and stress-intensity range (delta K). Salt water exerted a minor effect on da/dN in the HS and medium carbon steels. However, in the higher strength HY-100, a combination of salt water and high load ratios accelerated crack growth rates by approximately a factor of five. (Author)