Modelling for Fatigue Crack Growth Prediction in Mirage IIIO Frame 26.
AERONAUTICAL RESEARCH LABS MELBOURNE (AUSTRALIA)
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Constant- and variable-amplitude fatigue crack growth data have been obtained for A7-U4SG-T651 2214 aluminum alloy applicable to frame 26 of Mirage IIIO aircraft, enabling calibration of computer models of crack growth. Of the four crack growth retardation models examined-Wheeler, Willenborg, modified Willenborg and Crack Closure-the Wheeler and modified Willenborg models are the most satisfactory but both require calibration by test. Even so, crack growth is not accurately predicted when the specimen geometry and the test sequence are varied from those used in calibrating the models. Apart from the crack growth models, the main sources of inaccuracy in predicting crack growth are the inadequacy of the growth rate basic data, incorrect assumptions of crack shape, and uncertainty in stress history. Thus, crack growth life may not be confidently predicted to better than a factor of two on actual life and, in some cases, the factor may be as high as ten. Author
- Metallurgy and Metallography
- Numerical Mathematics