13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- plane, which means that hydrogen diffuses exclusively inside that plane. However, in the case of 2D approach, the maximum hydrostatic stress σ appears over a zone [13] allowing hydrogen to move towards diverse places. Fig. 3 shows a null loss of hydrogen diffusion directionality in points near the notch tip. The same figure indicates that the deeper is the considered point the higher is the loss of directionality, which is represented in the scheme shown in Fig. 4. Figure 4. Scheme of hydrogen diffusion path inside a material taking into account the diffusion model approaches considered in numerical simulations. 4. Conclusions • For high loading rates the hydrogen concentration predicted by the 1D approach to hydrogen diffusion in the material is practically equal to that predicted by the 2D approach, and therefore the influence of the geometric factor is not significant. • For low loading rates during the constant extension rate tensile (CERT) tests the loss of accuracy of results obtained with the 1D approach to hydrogen diffusion in the material becomes more significant due to the loss of directionality in diffusion path. • During the CERT tests, certain amount of hydrogen diffuses towards points placed out of the notch symmetry plane. This supposes a loss of hydrogen diffusion directionality in relation to the radial path obtained in 1D approach. • The loss of directionality of hydrogen diffusion is more accused for low extension rates during the CERT tests and points placed far away from the notch tip, it becoming more significant in sharp notches with low notch radius. • Obtained results reveal that the notch tip radius (sharp or blunt notched geometries) is the most relevant geometric parameter governing the loss of directionality of hydrogen diffusion, the notch depth exhibiting minor importance. • Hydrogen diffusion toward points placed out of the notch symmetry plane is strongly dependent on the distribution of hydrostatic stress inside the material. In the 1D approach the maximum hydrostatic stress location is a single point, whereas in the 2D approach it is a zone. Acknowledgements The authors wish to acknowledge the financial support provided by the following Spanish Institutions: Ministry for Science and Technology (MCYT; Grant MAT2002-01831), Ministry for Education and Science (MEC; Grant BIA2005-08965), Ministry for Science and Innovation (MICINN; Grants BIA2008-06810 and BIA2011-27870), Junta de Castilla y León (JCyL; Grants SA067A05, SA111A07 and SA039A08).
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