Effect of an anti-corrosion penetrant on the fatigue life in flight-simulation tests on various riveted joints

Comparative flight-simulation tests on four types of joints of 2024- T3 sheet material were carried out with and without application of the penetrant LPS-3. Types of joints were douhle strap joint with hi-lok bolts, asymmetric strap joint, lap joint with countersunk rivets and lap joint with dimpled holes. Observations on slip during the fatigue...

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...

Flight-simulation tests on notched elements

Tests were carried out on open-hole specimens, lugs and riveted strap joints of 2024-T3 and 7075-T6 materials. The effects of design stress level, truncating high-amplitude gust loads and omitting low-amplitude gust cycles were stuaied. Observations of the open-hole specimens include data on crack initiation, crack closure and damage increments....

Fatigue crack growth in aluminium alloy shee material under flight-simulation loading: effects of design stress level and loading frequency

Specimens of 2024-T3 and 7075-T6 were tested at 10, 1 and 0.1 cps. Values of mean stress in flight were 10.0, 8.5, 7.0, 5.5 and 4.0 kg/mm(2). The analysis of the results bears upon the frequency effect and its significance for inspection periods in service, the effect of stress level, a comparison between the two alloys, the prediction of crack...

The effect of load sequence on fatigue crack propagation under random loading and program loading

Crack propagation was studied in 2024-T3 Alclad sheet specimens under two types of random loading and under program loading with a short period and a long period. In the program tests Lo-Hi, Lo-Hi-Lo and Hi-Lo sequences were employed. The loads were based on a gust spectrum. The crack rates were about the same under random loading and program...

Crack propagation in 2024-T3 Alclad under flight-simulation loading effect of truncating high gust loads

Random flight-simulation tests were carried out in a similar way as in a previous investigation (NLR TH 68117) but now at lower stress levels. Truncation of the high gust loads again had a predominant effect. Increasing the truncation level considerably decreased the crack propagation rate.

Crack propagation in aluminum alloy sheet materials under flight simulation loading

A large number of flight-simulation tests were carried out on sheet specimens of 7075-T6 and 2024-T3 clad material. A gust load spectrum was adopted and a flight-by-flight loading was applied. The investigation is essentially concerned with macro-crack propagation though a few exploratory tests were conducted on the crack nucleation period. The...