Scaling of self-similar long fatigue crack growth in aluminium alloys

Propagation of long fatigue cracks in thin-sheet wrought aluminium alloys at constant stress ratio and constant stress amplitude (cyclic stress intensity factors ΔK range from about 10 MPa m1/2 to well below instability) is considered. The crack growth rates of aluminium alloys with strength-controlling precipitates that cannot be sheared by dislocations nearly coincide at a particular value of ΔK and increasingly diverge for increasing values of ΔK. The characteristic quantities specified by the point to which the fatigue crack growth curves converge are related to the shear modulus and the slip band spacing.