The elucidation of load history editing effect on fatigue crack growth by crack closure concept

The principal goal of this investigation is to elucidate the effect of load history omission on fatigue crack growth behavior from experimental determinations of opening loads. A FALSTAFF pseudo-random spectrum and its shortened spectra based on an amplitude-based editing technique are used to see the effect with two types of 2124-T851 aluminum specimens having a corner crack and a through-thickness crack at a bolt hole. A constant amplitude cycle is appended at the end of the spectra to monitor the variations of opening loads with crack advances. The crack aspect ratio under a constant amplitude loading is somewhat different from that under a random loading but there is no noticeable effect of history editing on the aspect ratio. The more omission of small amplitude cycles, the higher the opening loads, and the longer fatigue lives. The load history editing effect is closely related to the crack closure phenomena.