13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- straight line plot represents the notch sensitivity factor calculated using the Neuber’s formulation [7] given in Equation 28 where a0 is a material constant taken to be 0.2 for Ti-6Al-4V [1]. The plot shows that the new approach and the closed-form solutions give more accurate result compared to the existing Neuber’s formulation. 0 1 1 q a ρ = + (28) Figure 6. Notch sensitivity versus notch root radius for three notch sizes. 6. Conclusions A probabilistic framework based on Weibull’s weakest link extreme-value statistic that accounts for stress gradient at the notch root and the realistic microstructure of the material is presented. The fatigue notch factors, kf, estimated by this approach are compared with experimental kf. The comparison shows that the proposed method accurately predicts the fatigue notch factor of Ti-6Al-4V for the different Load ratios applied to the specimen geometry analyzed. Also, kf determined from a closed form solution of the proposed probabilistic approach validates the effectiveness of the proposed method. A plot of the notch sensitivity index against the notch root radius analyzed for the different load ratios as shown in Figure 6 shows that the proposed approach gives more accurate result compared to the existing Neuber’s formulation. Acknowledgements The authors of this paper express their profound gratitude to the Department of Defense for the financial support provided through research and educational program for HBCU/MSI (contract # W911NF-11-1-014, L. Russel and D. Stargel, Program Managers.) References [1] Haritos, G.K., Nicholas, T., and Lanning, D.B., Notch Size Effects in HCF Behavior of Ti-6Al-4V. Int. J. Fatigue, 21 (1999) 643–652.
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