SYMPOSIA PAPER Published: 01 January 1963

Estimation of Fatigue Performance of Aircraft Structures


The simulation of random service loads by cyclic loads is discussed. It is noted that their similarity can at present be shown on an empirical basis only. A few test programs are reviewed; a clear picture has not yet been obtained.

The results of program-fatigue tests on notched light alloy specimens and structures show that N¯n values are on the average larger than 1; and macrocrack propagation in sheet material is slower than predicted by the Palmgren-Miner rule. In addition to the amount of microcracking, the second damage parameter of residual stress at the tip of the crack is of great importance. Both parameters allow a qualitative understanding of the deviations from the Palmgren-Miner rule.

The rule is a useful tool to make rough life estimates in the early design stage, but the major difficulty is to obtain relevant and accurate S-N data. The rule is found to be unreliable in judging whether a certain type of service loading would contribute substantially to the damage induced by other loads.

Full-scale testing is considered to be indispensable to establish the fatigue performance of a new aircraft design. With present-day experimental facilities, a simulation of the anticipated load-time history in service is advised for such a test. Since program-fatigue testing may be useful for design studies, recommendations are made for planning the load sequence in this type of test.

Author Information

Schijve, J.
NLR, Amsterdam, The Netherlands
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Developed by Committee: E08
Pages: 193–215
DOI: 10.1520/STP44468S
ISBN-EB: 978-0-8031-6212-9
ISBN-13: 978-0-8031-6213-6