The use of standardized fatigue load sequences in coupon and component tests

Due to the development of servo hydraulic fatigue testing machines, fatigue tests under realistic loading conditions have become possible. In these tests, standardized load sequences can be applied. The paper describes the main properties of such sequences, including TWIST and FALSTAFF. Various examples of application of these sequences are...

Environmental fatigue crack propagation in metal/composite laminates

Flight simulation fatigue crack propagation tests with gust spectrum loading were carried out on 2024-T3/carbon-epoxy, 7475-T76l/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...

Engineering application of fracture mechanics to flight simulation fatigue crack propagation

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...

The effect of sheet edge working on the fatigue life under flight-simulation loading

Fatigue tests under flight-simulation loading have been performed on unnotched Alclad 2024-T3, anodised 2.0 mm thick sheet specimens, manufactured according to several machine-shop processes applied in the air craft industry. From the results it appears that milling is preferable to stamping. Rounding off the edges is also advantageous. The...

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...

The significance of cladding for fatigue of aluminium alloys in aircraft structures

Flight-simulation tests were carried out on sheet specimens notched "by an open hole (Kt = 2.66). The material was 2024-T3 in three conditions; Alclad, bare and chemically milled. The crack initiation period and the crack propagation period were considerably shorter for the Alclad material. The significance of the cladding, both for constant...

Fracture toughness and fatigue properties of the new aluminium alloy 7475-T76

Residual strength tests have been performed on 610 mm wide centre cracked panels. During the tests, stable crack growth was filmed and crack opening displacements were measured. Fracture toughness was determined using the method of Feddersen. Flight simulation fatigue tests were carried out to investigate the crack propagation properties. A...