Fatigue Crack Growth Under Programmed Equivalent of FALSTAFF Spectrum

Optical fractography was used to estimate small notch13; crack growth under programmed FALSTAFF loading in an13; Al-Cu alloy. It was able to handle crack sizes as low as 25 microns and growth rates Over two orders of magnitude. 13; Randomized Mini FALSTAFF load sequence was modified13; into a programmed load equivalent with major loads either13; preceeded or succeeded by marker loads. Crack growth rate13; under programmed FALSTAFF spectrum as estimated by optical13; fractography conformed to compliance based estimates on a13; SE (T) specimen. Long crack growth rates under programmed13; and randomized mini FALSTAFF spectrum were essentially13; similar. Spectrum load fatigue crack growth was studied13; in central hole coupons under notch inelastic conditions.13; Scatter in growth rates for small notch cracks was found13; to be of the same magnitude as that of long cracks.13; Multiple fatigue cracks are observed at the notch root,13; and they appear to influence each other.13; 13