13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- Figure 10. Finite element displacements Figures 11 and 12 present the comparison between radial and tangential strains given by finite element approach and experimental data. In order to clarify visibility, we choose to represent experimental measurements for extreme rings for radius n°6. For radius n°6, we can observe a very good agreement between experimental and simulation results. However, the results in terms of tangential strains present differences induced by the development of a crack in the end of test. At the moisture content of 8%, mappings of RR , TT and RT are posted in Figures 13 to 15. About radial stresses, we can observe an evolution of heart (compression state) toward outside (tension state) with a radial homogeneity. The combination of tangential and shear stresses illustrates that the crack growth initiation is based on a coupling between tangential tensions and shear state according to a mixed mode configuration. Figure 11. Comparison between experimental and numerical radial strains along radius n°6
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