13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- closure and residual stress effects, especially under the low R-ratios but not under the high R-ratios. The natural small crack growth rate data showed that the “fanning” effect at the near-threshold region is mainly due to the material microstructural scatter, which cannot be determined by long crack tests. Both silicon-based replication and marker band techniques offered very good crack detection resolutions. The C(T) and SENT data were then combined to develop an NRC material short-long crack model for 7075-T73 aluminum alloys. Using this model and the NRC in-house crack growth tool CanGROW, a good life estimation was achieved for coupon tests under transport loading spectra. Shortcomings were found for a legacy model that includes the Forman equation and Hsu retardation in the spectrum load life analysis. The CC-130 component case showed the difference in the DTA analyses using the legacy and NRC material models, for both PBP and MSD scenarios. Component test data are needed to further validate the DTA analyses and their differences. Tests cases on total fatigue life estimation are also needed to further validate the developed small crack material model. Acknowledgements This work was carried out with the financial support of Defence Research and Development Canada and NRC, Projects ‘‘Short Crack Model Development for Helicopter Structural Life Assessment” and “Integrated Structural Life Assessment Method for the CF Air Fleets”. Thanks to Defense Science and Technology Organization (DSTO) of Australia for providing some coupon test results. References [1] M. Liao, G. Renaud, Y. Bombardier, R. Desnoyers, T. Benak, Short crack model development for aircraft structural life assessment – final report, LTR-SMPL-2011-0239, Sept. 2011. [2] J.K. Donald, G.H. Bray, R.W. Bush, An Evaluation of the Adjusted Compliance Ratio Technique for Determining the Effective Stress Intensity Factor, 29th National Symposium on Fatigue and Fracture Mechanics, ASTM STP 1332, T. L. Panontin, S. D. Sheppard, Eds., American Society for Testing and Materials 1998. [3] D.L. Ball, J.K. Donald, M.A. James, and R.J. Bucci, The relationships between crack closure, specimen compliance and ‘effective’ fatigue crack growth rate, Proceedings of the 2011 ICAF, Montréal, June 1-3, 2011 (pp.265-276). [4] J.C. Newman, Jr., Analyses of Fatigue Crack Growth Databases for Use in a Damage Tolerance Approach for Aircraft Propellers and Rotorcraft, DOT/FAA/AR-07/49, 2007. [5] G. Renaud, M. Liao, Y. Bombardier, Improved stress intensity factor solutions for surface and corner cracks at a hole, 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, April 2012, Honolulu, Hawaii. [6] R.W. Bush, R.J. Bucci, P. E. Magnusen, and G.W. Kuhlman, Fatigue crack growth rate measurements in aluminum alloy forgings: effects of residual stress and grain flow, Fracture Mechanics: 23rd Symposium. ASTM STP 1189. R. Chona, Ed., ASTM, 1993, pp.568-589. [7] R. Ogden, D. Hartley, L. Meadows, Determination of the RAAF C-130J-30 Hercules wing Structural life of type through full scale fatigue testing, 2011 ASIP Conference, San Antonio. [8] T. Deiter, Hsu model, AFRL-RB-WP-TR-2008-3, 2004. [9] Y. Bombardier, M. Liao, G. Renaud, A new crack growth analysis tool for the assessment of multiple site fatigue damage, Proceedings of the 2010 Aircraft Airworthiness & Sustainment Conference, Austin, USA, 2010. [10] J.C. Newman, A. Brot, and C. Matias, Crack-growth calculations in 7075-T7351 aluminum alloy under various load spectra using an improved crack-closure model, Engineering Fracture Mechanics, 71 (2004) 2347–2363. [11] R.L. Circle, F.M. Conley, A Quantitative Assessment of the Variables Involved in Crack Propagation Analysis for In-service Aircraft, J. of Aircraft, 18 (1980) 562-569.
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