Threshold and Near Threshold Fatigue Crack Growth of Five Cast Steels at Room Temperature and −45°C

Abstract

Threshold and near threshold fatigue crack growth behavior was obtained for five carbon or low alloy cast steels at room temperature and −45°C (−50°F) with the load ratio R=0.05 and 0.5. Mean stress effects at both temperatures appear to be substantially dependent upon crack closure. ΔKth did not correlate well with other mechanical properties such as Su , Sy , Sy ′ or Sf . Threshold and near threshold fatigue crack growth resistance was generally improved at −45°C despite the fact that this temperature was below the NDT temperature for three of the five cast steels. SEM fractography also established that the NDT temperature is not associated with a possible ductile-brittle constant amplitude fatigue crack growth transition in cast steels. ΔKth values for these five cast steels appear to be quite favorable relative to values found in the literature for wrought steels.