Variability of fatigue crack growth properties for 2024-T3 aluminium alloy

Discussions between D-BAA and the NLR have shown that significant variability in fatigue crack growth properties is possible for the industry standard damage tolerant aluminium alloy, 2024-T3 sheet. This is important for two reasons: (1) design assumptions and (2) comparisons of different candidate materials, such as 6013-T6, with 2024-T3....

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,...

A test plan for sustained load fracture control verification

An example test plan for sustained load fracture control verification is presented. Two sustained load fracture problems have been chosen: stress corrosion cracking of titanium alloy Ti-6Al-4V, and gaseous hydrogen embrittlement of the nickel-base superalloy Inconel 718. The plan is worked out in detail, including materials and heat treatments,...

Spacecraft sustained load fracture control

The opportunities for sustained load fracture control in spacecraft are indicated. Emphasis is given to verification by small-scale laboratory testing.

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...

Manoeuvre spectrum fatigue crack propagation in aluminium alloy sheet materials

2024-T3, 2048-T851, 7075-T6 and 7475-T761 aluminium alloy sheets were compared for fatigue crack propagation resistance under manoeuvre spectrum and constant amplitude loading. For manoeuvre spectrum loading 7475-T761 was superior overall, and this superiority is most probably due to superior toughness of this alloy. In more detail, 2024-T3 was...

Environmental fatigue crack propagation in metal/composite laminates: interim report no. 1

Plight simulation fatigue crack propagation tests with gust spectrum loading were carried out on 2024-T3/carbon-epoxy, 7475-T761/carbon-epoxy and Ti-6Al-4V/carbon-epoxy laminates with nominal weight savings of 30% as compared to equivalent 2024-T3 panels. The performance of the 2024-T3/ carbon-epoxy laminates was much superior to those of the...

Flight simulation fatigue crack propagation evaluation of candidate lower wing skin materials with particular consideration of spectrum truncation

Flight simulation fatigu-e crack propagation tests were carried out on 2024-T3, 7475-T761 and mill annealed Ti-6A1-4V sheet in thicknesses up to 3 miri and representative for transport aircraft lower wing skin stiffened panels of end load capacities 1.5 and 3 MN/m. The performance of 2024-T3 was much superior, owing mainly to greater retardation...

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...