Propagation Behavior of Long Crack in Low Cycle Fatigue Regime.

Fatigue crack propagation behavior of a center cracked plate was observed by an optical microscope in the low cycle fatigue regime. The fatigue tests were carried out under a stroke-controlled condition. The crack propagation rate da/dN was proportional to the crack length a and the crack propagation law could be expressed by da/dN=Ceαta, where C and α are constants and Δet is the reversed nominal strain range. Also, the nominal stress at maximum load was inversely proportional to the crack length normalized by specimen width a/W. Furthermore, the crack growth behavior in the case of low cycle fatigue of the present experiment was compared to that in the case of ductile fracture of a center cracked plate. In both cases, the crack growth behavior could be correlated with the crack length and the crack opening geometry.