ICF13B

13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- Fig.4 The crack growth rate in parent material and weld nugget 4. Conclusion The crack growth rate in weld nugget of Al-Li alloy 2198-T8 friction stir welded was mainly decided by the microstructure, not the R ratio as common understanding. Acknowledgement This paper is sponsored by “National Natural Science Foundation of China (11002111) References [1] P. Cavaliere, M. Cabibbo, F. Panella, A. Squillace, 2198 Al–Li plates joined by Friction Stir Welding: Mechanical and microstructural behavior, Materials & Design, Volume 30, Issue 9, 2009, pp. 3622–3631. [2] G Bussu, P.E Irving. The role of residual stress and heat affected zone properties on fatigue crack propagation in friction stir welded 2024-T351 aluminium joints, International Journal of Fatigue, Volume 25, Issue 1, 2003, pp.77-88. [3] R John, K.V Jata, K Sadananda, Residual stress effects on near-threshold fatigue crack growth in friction stir welds in aerospace alloys, International Journal of Fatigue, Volume 25, Issues 9–11, 2003,pp.939-948. [4] P. Cavaliere, A. De Santis, F. Panella, A. Squillace, Effect of anisotropy on fatigue properties of 2198 Al–Li plates joined by friction stir welding, Engineering Failure Analysis, Volume 16, Issue 6, 2009, pp.1856–1865 [5] P.M.G.P. Moreira, M.A.V. de Figueiredo, P.M.S.T. de Castro, Fatigue behaviour of FSW and MIG weldments for two aluminium alloys, Theoretical and Applied Fracture Mechanics, Volume 48, Issue 2, 2007, pp.169–177 [6] M. Pedemonte, C. Gambaro, E. Lertora, C. Mandolfino, Fatigue assessment of AA 8090 friction stir butt welds after surface finishing treatment, Aerospace Science and Technology, 2012, in press. [7] R.S.Mishra, Z.Y.Ma, Friction stir welding and processing, Materials Science and Engineering: R: Reports, Volume 50, Issues 1–2, 2005, pp. 1–78. [8] Z.L. Hu, X.S. Wang, S.J. Yuan, Quantitative investigation of the tensile plastic deformation characteristic and microstructure for friction stir welded 2024 aluminum alloy, Materials Characterization, Volume 73, 2012, pp. 114–123. [9] B. Holper, H. Mayer, A.K. Vasudevan, S.E. Stanzl-Tschegg, Near threshold fatigue crack growth at positive load ratio in aluminium alloys at low and ultrasonic frequency: influences of strain rate, slip behaviour and air humidity, International Journal of Fatigue, Volume 26, Issue 1, 2004, pp.27-38. [10]Krueger Ronald. The virtual crack closure technique: history, approach and applications. NASA/CR-2002-211628.

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