Development of Statistical Fatigue Failure Characteristics of 0.125-Inch 2024-T3 Aluminum Under Simulated Flight-by-Flight Loading
Final rept. Aug 1972-Mar 1974
BOEING COMMERCIAL AIRPLANE CO SEATTLE WA
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Thirty-two unique multidetail specimens were tested to develop a data base for investigating the statistical materialsstructures fatigue failure characteristics of 2024-T3 aluminum alloy in the form of 0.225-in.-thick sheet. The test loading was a random-load, flight-by-flight loading block spectrum repeated to obtain crack initiation. Six different basic spectra, representative of cargotransport or gust load flights, were applied to the specimens. Fatigue crack initiation was detected and controlled to a nominal crack length of about 0.04 in. from the edge of the hole by a painted crack detection circuit system. After detection of crack initiation, each hole was restored to an undamaged state by oversizing and coldworking. A statistical analysis of the data by previously developed maximum likelihood methods is presented for both scale and shape parameters of the log-normal and two- parameter Weibull distributions.
- Metallurgy and Metallography