Development of Titanium and Steel Fatigue Variability Model for Application of Reliability Analysis Approach to Aircraft Structures

An investigation of the fatigue performance test scatter in titanium alloys and steels was made with the intent of identifying their variability in terms of a distribution and its shape parameter. The two-parameter Weibull distribution was selected for matching the fatigue variability of these two m...

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Bibliographic Details
Main Author: Whittaker, I C
Format: Report
Language:English
Subjects:
Aircraft
AIRFRAMES
ANALYSIS OF VARIANCE
CRACK PROPAGATION
CRACKS
FATIGUE(MECHANICS)
FRACTURE(MECHANICS)
Metallurgy and Metallography
RELIABILITY
STEEL
TABLES(DATA)
TITANIUM ALLOYS
WEIBULL DENSITY FUNCTIONS
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Summary:An investigation of the fatigue performance test scatter in titanium alloys and steels was made with the intent of identifying their variability in terms of a distribution and its shape parameter. The two-parameter Weibull distribution was selected for matching the fatigue variability of these two materials. About 1200 groups of titanium alloy and 800 groups of steels were collected and analyzed to determine the feasibility of establishing a typical distributional Weibull shape parameter for these materials. A Weibull distribution shape parameter of 3.0 is suggested for titanium alloys and those steels with a 240-ksi strength level or less. Steels having greater than a 240- ksi strength level seem better represented by a shape parameter of 2.2. In a further study, the choice of a distribution most aptly matching fatigue variability was explored with the use of previously collected extensive aluminum alloy and the titanium alloy data.