Effects of Stress Ratio on Fatigue Crack Growth Rates in X70 Pipeline Steel in Air and Saltwater

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