Crack propagation in aluminum alloy sheet materials under flight simulation loading

Crack propagation in aluminum alloy sheet materials under flight simulation loading

Schijve, J.
Jacobs, F.A.
Tromp, P.J.

National Aerospace Laboratory NLR

1968-12-31

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 major trends emerging from tests with a variety of loading programs are: 1. The omission of taxiing loads from the ground-to-air cycles did not affect the crack propagation. 2. The sequence of the gust cycles in a flight (random, programmed, reversed gust cycles) did not have a significant influence on the crack propagation. 3. Omission of gust cycles with small amplitudes systematically increased the crack propagation life. 4. The most predominant effect on the crack propagation was coming from the maximum gust amplitude included in the test. Increasing this amplitude gave a large increase of the crack propagation life. 5. Application in each flight of a single gust load only, namely the largest upward gust load, increased the crack propagation life three times. 6. Omission of the ground-to-air cycle increased the life 1.5-1.8 times. The discussion and the analysis of the results include such aspects as fractographic analysis, possible mechanisms for interaction effects between load cycles of different magnitudes and damage calculations. The conclusions at the end of the report have a number of implications for testing procedures to be applied in full-scale testing aiming at crack propagation data for fail-safe considerations. A recommendation is made for selecting the maximum load level in such a test. Recommendations for further study are also made.

http://resolver.tudelft.nl/uuid:df6c32f5-1452-46a9-880e-b35bdfff44ee

Nationaal Lucht- en Ruimtevaartlaboratorium

Campus only

NLR-TR 68117 U

Aerospace Engineering Reports

report

(c) 1968 National Aerospace Laboratory NLR