13th International Conference on Fracture (ICF13) June 16–21, 2013, Beijing, China An example is shown in Figure 8 where different blocks at different stress levels are applied and crack propagation probabilities consecutively calculated for each loading block. Cracks are grown using Paris’ law and three curves are calculated, a most probable path by choosing the highest probabilities, and a worst and best case scenarios. 6. Conclusions In this paper subcritical crack propagation diagrams have been illustrated for fatigue and environmentally assisted cracking. The limit condition for subcritical crack propagation in the proposed framework is represented by Kitagawa-like diagrams combined with the El Haddad correction factor. Reliability methods for the estimation of probability of crack propagation for the diagrams shown have been proposed. Probability of crack propagation has been evaluated by using first and second order reliability methods (FORM/SORM) as well as Monte Carlo simulation. Preliminary validation of the developed framework for fatigue has been shown, and more experimental data are currently being gathered for further validation of this diagram and for EAC diagrams. An example application of the developed framework to probabilistic subcritical crack growth has been illustrated. Further work is needed to apply the framework to multiple R-ratios data, and to extend to variable amplitude loading. Sensitivity analysis is planned to study the effects of selected stress and defect distributions on the reliability of the system. References 1. A. Keshtgar, A. Arcari, N. Iyyer, M. Kittur, N. Phan, “A Reliability Approach for Subcritical Crack Propagation in High Cycle Fatigue”, 15th Australian International Aerospace Congress, Melbourne Convention Centre, 25-28 February 2013 2. J. P. Gallagher, et al. “Demonstrating the effectiveness of an inspection system to detect cracks in safety of flight structures”, Proceedings of a Workshop on Materials State Awareness National Research Council, Emily Ann Meyer Editor 3. Arcari A., Apetre N., Iyyer N., Nickerson W., “Probabilistic failure diagram for environmentally assisted cracking”, International Committee on Aeronautical Fatigue and Structural Integrity, Jerusalem, Israel, June 3 – 7, 2013 4. Arcari, A., Apetre, N., Iyyer, N., Sarkar, S., Dowling, N.E., Stanzl-Tschegg, S., Phan, N., Rusk, D., Kang, P., Vasudevan, A.K.,, “Influence of superimposed VHCF loadings in cyclic fatigue and fracture of 7075-T6 aluminum alloy,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 23 - 26 Apr 2012, Honolulu, Hawaii 5. L. Lazzeri, U. Mariani, Application of Damage Tolerance principles to the design of helicopters, International Journal of Fatigue, Volume 31, Issue 6, June 2009, Pages 10391045, ISSN 0142-1123, 10.1016/j.ijfatigue.2008.05.010. 6. Noroozi, A. H., Glinka, G., Lambert, S., (2007), “A study of the stress ratio effects on fatigue crack growth using the unified two-parameters fatigue crack growth driving force”, Int. J. Fatigue, vol. 29, n. 9-11, p. 1616-1633
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