13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- small, suggesting that the two stiffness coefficients could be assumed equal and given from the continuum solution, following [17] for example. Figure 5. Normalised cell energy vs size ratio under hydrostatic compression. In the case of pure twist the cell energies were found to be dependent on , Fig. 6. While this is similar to the case of hydrostatic compression the effect of particle size is substantially larger. All relative displacements between P0 and the principal particles were zero, conforming to Eq. (11). The relative displacements between P0 and octahedral particles were zero axial and non-zero transversal, again conforming to Eq. (11). This means that the only activated linear springs in the site-bond model are the shear springs in octahedral direction with stiffness Ks o. Figure 6. Normalised cell energy vs size ratio under pure twist The calculated relative rotations between P0 and the particles in the two directions are shown in Fig. 0.995 1.000 1.005 1.010 1.015 1.020 1.025 1.030 0 5 10 15 Normalised energy, Ω/Ω0 Cell size / Particle size 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 0 5 10 15 Normalised energy, Ω/Ω0 Cell size / Particle size
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