A critical analysis of fatigue-crack propagation data for 2024-T3 aluminum.
Kish, Robert Alan
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Fatigue-crack growth data for 2024-T3 aluminum was used to evaluate the accuracy of Forman's equation. Forman's equation was found to predict from one-third to twice the observed cycles to a given crack length when applied to multiple cyclic stress ratios. An alternative approach was developed, based on the observed data, which is applicable to analog or digital fatigue-crack growth prediction. Data acquisition based on constant increment of crack length has been found to yield inadequate definition of the crack-growth curve in the low-cycle range for the successful application of the method. An expression was developed which extends the application of the crack-closure concept to the entire range of cyclic stress ratio. An effective root-mean-square stress was defined which shows indications of good correlation with the magnitude of the crack-growth curves.
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