Near-threshold fatigue crack growth behavior in metals

Abstract Near-threshold fatigue crack growth rate (FCGR) behavior in six alloy systems (iron, aluminum, copper, magnesium, nickel and titanium) is extensively reviewed and compared. It is suggested that a unique effective threshold stress intensity range, ΔK th , eff , exists for each alloy system in room temperature air. The value of ΔK th , eff was found to be directly proportional to Young's modulus, E Furthermore, Young's modulus normalizes the near-threshold fatigue crack propagation behavior in the various alloy systems investigated. The present findings are consistent with the existing threshold FCGR theories that relate ΔK th , eff to E . Additional research is required, however, to incorporate crack closure phenomena in these near-threshold FCGR theories to assess the influence of microstructure, load ratio and environment.