ISSN: 0090-3973
Page Count: 6

Effects of Stress Ratio on Fatigue Crack Growth Rates in X70 Pipeline Steel in Air and Saltwater
Vosikovsky, O
Research scientist, Canada Centre for Mineral and Energy Technology, Physical Metallurgy Research Laboratories, Ontario

Abstract

Fatigue crack growth rates in an X70 pipeline steel were measured over a wide range of stress intensities in laboratory air and in 3.5% sodium chloride solution under free corrosion and cathodic (coupled to zinc) potentials. The effects of stress ratio in all these environments and of cyclic frequency in the sodium chloride solution were studied. The results are compared with fatigue crack growth rates measured previously in lower strength X65 steel. The stress ratio strongly influences the fatigue crack growth thresholds and close-to-threshold growth rates. With increasing stress intensity range, the stress ratio effect decreases similarly in both air and aqueous environments. The lower cyclic frequency enhances corrosion fatigue crack growth rates at intermediate stress intensity ranges, as was observed earlier in X65 steel.

Keywords:
corrosion fatigue, crack propagation, steels, stress ratio, frequency, cathodic protection, saltwater, fatigue tests, environmental tests

Paper ID: JTE10597J
DOI: 10.1520/JTE10597J
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