The wrought alloys Nimonic 90, Nimonic 901, Udimet 520, IN-718 and IN-738, and the castings IN-718 and IN-738LC were fatigue tested at cyclic stress amplitudes near threshold at room temperature and a stress ratio R = -1. Fatigue crack initiation and crack growth were studied.
A study was made of fatigue crack initiation and growth in two high-strength Al-alloys (2024 and 7475) differing in mechanical properties and microstructure. Emphasis was on performing the experiments at low load amplitudes slightly below and above the high-cycle fatigue limit (0.9 to 1.4 times the fatigue limit, 0.3 to 0.9 times the yield strength). Attempts were made to investigate the effect of stress ratios (R between -1 and 0.7), ...
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