13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- By considering a classical Tsai-Wu's criterion written in a stress form, the Figure 16 shows us the mapping of the function f by noting its concentration in the crack growth zone vicinity. Figure 16. Shear stress mapping at 8% of moisture content 5. Conclusion The strain and fracture process due to the natural drying of green wood slice have studied in this work. The experimental device, composed of a sensitively balance, a video camera, a slice with tracked, have provided to own the displacement in the slice axis during drying phase. The experimental protocol is completed with a numerical model integrating mechano-sorptive effect. In this context, a finite element model based on an incremental formulation is developed. By using comparisons between finite element results and experimental marker tracking data, the stress field is computed in the cylindrical orthotropic radial-transverse reference by taking into account cylindrical defects induced by conditions of the tree growth. By performing a strength criterion based on Tsai-Wu or Hill approaches, the numerical model allows to focusing the crack growth initiation localization. References [1] A.P. Schniewind, R.A. Pozniak, On the fracture toughness of Douglas fir wood, Engineering Fracture Mechanic, 1971, 223–230. [2] I.D. Cave, A theory of the shrinkage of wood, Wood Science and Technoly, 1972, (6), 284-292. [3] P. Bekhta, I. Ozarkiv, S. Alavi, S. Hiziroglu, A theoretical expression for drying time of thin lumber, Bioresource Technoly, 2006, (97), 1572–1577. [4] F. Dubois, J. M. Husson, N. Sauvat, N., Manfoumbi Modeling of the viscoelastic, mechano-sorptive behavior in wood, Mechanics of Time Dependent Materials, doi: 10.1007/s11043-012-9171-3, 2012. [5] S.J. Kowalski, A. Smoczkiewicz-Wojciechowska, Stresses in dried wood, Modeling and experimentation, Transp Porous Med., 2007, (66), 145-158.
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