No abstract

No abstract

No abstract

The threshold value for fatigue crack growth of a medium carbon steel was increased when the test-environment was changed from air to an aggressive H,S-containing brine. This increase in fatique threshold was shown to be caused by corrosion product-induced crack closure. Further, the fatigue threshold and crack closure level were shown to be dependent on the growth rate history in approaching threshold. The differences in fatigue crack growth rate and fatigue threshold resulting from test procedure and growth rate history were significantly reduced by employing the effective stress intensity concept. NOMENCLATURE a = crack length COD = crack opening displacement CTOD = crack tip opening displacement daldN = crack growth rate per cycle R = load ratio equal to K,,,IK,,, K = stress intensity K,,,, K,,, = maximum and minimum stress intensity per cycle A K = cyclic stress intensity AKth = cyclic threshold stress intensity P,,, = crack opening load KO,, = crack opening stress intensity AKefF = effective stress intensity, equal to Km,, -KSP 0, = monotonic yield stress = cyclic yield stress E = Young's modulus.

No abstract