Abstract
The fatigue crack growth rates and their thresholds of mild steel were measured in natural sea water and in air. The influence of natural sea water on fatigue crack growth behavior was discussed. The following conclusions can be drawn:
(1) The threshold stress intensity factor ranges ΔKth were 6.0MN/m3/2 in air and 3.8MN/m3/2 in natural sea water.
(2) The correlation between, the stress intensity factor range ΔK and the rate of crack growth dl/dN for mild steel follows Paris's law both in air and sea water:
dl/dN=C(ΔK)m
where m is the slope of the correlation, and is 5.6 in air and 3.9 in sea water respectively.
(3) The rate o crack growth in sea water is 5 to 10 times faster than that in air.
