Influence of gust spectrum variations on fatigue crack growth behaviour of damage tolerant aluminium-lithium sheet materials

Flight simulation fatigue growth tests were done on 1.6 mm thick sheets of the damage tolerant aluminium-lithium (Al-Li) alloys 2091-T84 and 8090-T81 in comparison with the industry standard conventional damage tolerant alloy 2024-T3. The flight simulation load spectrum, the gust spectrum MINITWIST, was used in four versions: untruncated,...

Microstructural and fractographic analysis of fatigue crack propagation in 2024-T351 and 2324-T39

Differences in the fatigue crack propagation rates of 2024-T351 and 2324-T39 are explicable from differences in microstructures. The slope changes (transitions) in the crack propagation curves are probably associated with the plastic zone sizes being equal to certain microstructural dimensions. As a consequence of different chemical compostion...

Comparison of fracture toughness in titanium alloys IMI 550 and IMI 551

Fracture toughness tests on two high strength titanium alloys, IMI 550 and 551, showed that the higher strength alloy, IMI 551, had a much lower toughness. The alloys were very similar in microstructure and fracture mechanisms. A number of model formulations for predicting fracture toughness were compared with the experimental results. This...

Heat treatment studies of aluminium alloy type 7050 forgings. Interim report no. 3: Corroded-specimen fatigue tests and SCC propagation tests

The influence of previous corrosion on the fatigue life was investigated. It was foimd that a slight corrosive attack could drastically reduce the fatigue life. The damaging effect of corrosion was greater for the alloy AA 7050 than for AZ 74.61. It could be established that fatigue cracks initiated from various corrosion pits. A second series...

Environmental effects on crack grwoth in flight-simulation tests on 2024-T3 and 7075-T6 material Supplement: Compilation of test data from an investigation on the effect of environment on crack growth under flight-simulation loading

Flight-simulation tests based on a standardized gust load spectrum were carried out in normal air, very dry air and salt water. Specimen thicknesses were t = 2 mm and t = 10 mm, mean stress in flight was 70 or 55 MN/m². In all cases a significant effect of the environment was found. Fatigue lives for t = 10 ram were much shorter than for t = 2...

Effects of crack plane orientation transitions on flight simulation fatigue crack propagation in a high strength aluminium alloy (7050)

The effects of flat to slant fracture transitions on flight simulation fatigue crack propagation in specimens of 7O5O aluminium alloy forgings are discussed. For specimens containing flat, shearlipped, or full slant fractures at similar crack lengths the crack resistance (R curve) approach appears to provide an explanation for differences in the...