13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- Within 16 samples, no sample with perfect anti-symmetric distribution of the two crack paths has been found. This is because the number of experimental samples is too few to include a sample with sufficiently homogenous material property and symmetrical boundary condition at the same time. The typical crack patterns can be classified into two groups: (1), one main crack path develops from either one of the two notches; (2), the two crack paths are more or less anti-symmetrically distributed. From experiments, some cracks bifurcate at the end of experiments. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Figure 3. The typical crack paths projection into YZ plane under force boundary condition of loading rate 5N/s Among 200 numerical samples, we find the samples, whose crack paths coincide with experimental results. In order to make further comparison between the simulation results and experimental results, the stress distribution of simulation has been converted into photo elastic fringe patterns. Fig. 5 and 6 shows the experimental photo-elastic fringe patterns and the numerically synthesized fringe patterns. From these comparisons, the crack growth processes of these two samples are successfully simulated by the method proposed in this paper. 4.1 4.2 4.3 4.4 Figure 4. Photo elastic frames of experiments’ final stages, 100 t s (with colors reversed) Experiments 40 t s 70 t s 100 t s (a), fringe patterns of experimental sample 4.1
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