HEAT TREATMENT STUDIES OP ALUMINIUM ALLOT FORGINGS OF THE AZ74.61 TYPE INTERIM REPORT NO. 3: FATIGUE CRACK PROPAGATION PERFORMANCE UNDER MANOEUVRE SPECTRUM LOADING

摘要

The fatigue crack propagation performance of the alloy AZ74.61 under manoeuvre spectrum loading was studied. The crack propagation behaviour was also compared with that of the American forging alloy AA 7050, not only for simulated manoeuvre loading but also for simulated gust loading and programme loading.nIt was found that, at comparable strength, the alloy aft. 7050 was superior to AZ74.6l. Macro-fractographic observations revealed that the crack propagation behaviour differed with respect to heat treatment, type of the load spectrum and specimen type. These observations emphasize the complexity of fatigue damage accumulation under variable amplitude loading.