13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- intensity factor range ΔK is not too large, in other words, if only the fatigue crack is not at the later stage of accelerated growth region, the theoretical values are totally larger than that of experimental data, so the predicted results obtained by the inverse deduced equations tend to security. 5. Conclusions (1) The fatigue life of GH4133B superalloy is measured, and the theoretical fatigue life is calculated, and the P-S-N curves at various survival probabilities are obtained. It is found that the theoretical fatigue limit agrees well with experimental one, and the fatigue life of GH4133B superalloy can accurately be estimated by the P-S-N curves. (2) The modified Chaboche model can predict the accumulated damage of GH4133B superalloy preciously. Higher stress amplitude will result in a higher proportion of the fatigue life in stage I of fatigue crack initiation and small crack propagation to the total fatigue life, which is unfavorable to monitor the accumulative fatigue damage and to prevent fatigue fracture in the components. (3) A modified Paris formula is achieved by introducing a threshold stress intensity factor range. The comparison between theoretical curves and experiment data shows that the modified Paris formula can not only be used to predict the value of threshold stress intensity factor range at different stress ratio, but also can describe the fatigue crack propagation behavior accurately. (4) Based on the measurement data of fatigue striations and the modified Paris formula, the crack propagation rate equations and external loads are inversely deduced and calculated. It is found that the inverse deduced equations based on the fractography inverse model can predict the fatigue crack propagation behavior, and the predicted results tend to security. Acknowledgements The authors gratefully acknowledge the finanicial support of the Research Foundation of Education Burean of Hunan Province, China (No. 11B125). References [1] Q.P. Zhang, Z. Zhang, H.S. Wu, S.Z. Zuo. Physical and mathematical models of fatigue propagation and final rupture regions for metallic materials. Acta Aeronautica and Astronautica Sinica, 21(s), (2000) s11–s14. (in Chinese) [2] E.J. Xu.The Effect of defects, damage and micro crack on total life and reliability of aeroengine components in service. Aeroengine, 29(2), (2003) 11–15. (in Chinese) [3] J. Schijves. Fatigue damage in aircraft structures, not wanted, but tolerated? Int. J. Fatigue, 31(6), (2009) 998–1011. [4] A. Fatemi, L. Yang. Cumulative fatigue damage and life prediction theories: A survey of the state of the art for homogeneous materials. Int. J. Fatigue, 20(1), (1998) 9–34. [5] P. Starke, F. Walther, D. Eifler. New fatigue life calculation method for quenched and tempered steel SAE 4140. Materials Science and Engineering A, 523(1–2), (2009) 246–252. [6] B. Sun, Y. Guo. High-cycle fatigue damage measurement based on electrical resistance change considering variable electrical resistivity. Int. J. Fatigue, 26(5), (2004) 457–462. [7] D. Huang, P. C. Xu, Y.M. GUO. A research on the estimation of remaining service life for metals in fatigue. Journal of Experimental Mechanics, 18(1), (2003) 113–117. (in Chinese) [8] D.Y. Hu, R.Q. Wang. Experimental study on creep-fatigue interaction behavior of GH4133B superalloy. Materials Science and Engineering: A, 515(1–2), (2009) 183–189. [9] X.Y. Luo, R.G. Zhao, Y.Z. Jiang, H.C. Li, X.J. Li, X.H. Liu. Statistical analysis on mechanical properties of GH4133B superalloy used in turbine disk of aero-engine at ambient temperature. Chinese Journal of Mechanical Engineering, 46(22), (2010) 75–83. (in Chinese) [10]S.A. Padula II, A. Shyam, R.O. Ritchie, W.W. Milligun. High frequency fatigue crack propagation behavior of a nickel-base turbine disk alloy. Int. J. Fatigue, 21(7), (1999) 725–731.
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