13th International Conference on Fracture June 16–21, 2013, Beijing, China 8 0 1000 2000 3000 4000 5000 6000 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 Crack depth, mm Time, h Fracture mechanics Damage mechanics Experimental data Spec. 5 Crack initiation 0 500 1000 1500 2000 2500 3000 3500 3.0 3.5 4.0 4.5 5.0 5.5 Spec. 6 Crack depth, mm Time, h Fracture mechanics Damage mechanics Experimental data Crack initiation (a) (b) Figure 6. Comparisons of crack depth variations predicted by using fracture mechanics and continuum damage mechanics approaches 5. Conclusions The main conclusions drawn from the study are listed as follows: (a) For fracture mechanics approach, the convergence of the relation between the crack depth and propagation time does exist if the maximum crack growth increment is small enough. (b) Both fracture mechanics and continuum damage mechanics approaches in conjunction with the FE technique can give reasonable predictions of the crack profile when compared with the experimental results of thumbnail crack specimens tested under tension. (c) The propagation time can also be appropriately predicted by the damage mechanics approach, while it is far from satisfactory when using the facture mechanics method. For the purpose of a more accurate prediction, the different constraint effects between the CT and thumbnail crack specimen need to be carefully considered. (d) The crack initiation time can also be predicted by the damage-based approach presented in the study. Acknowledgements This work is financially supported by National Natural Science Foundation of China (Contract No. 50835003). The authors would also like to thank Prof. T.H. Hyde and Prof. W. Sun at University of Nottingham for the helpful discussion with them. References [1] Smith SD, Webster JJ, Hyde TH. Creep behaviour of a stationary, semicircular surface crack. Engng Fract Mech 1988;30:105-16. [2] Yoon KB, Park TG, Saxena A. Creep crack growth analysis of elliptic surface cracks in pressure vessels. Int J Pres Ves Pip 2003;80:465-79.
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