13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- The predictive bounds from the model compared to both experimental data and the Master Curve are given in Fig. 3 for the un-irradiated material for both the β =2.7 (left) and β =4 (right) carbide size distributions. It can be seen that our model provides a good fit of the experimental data for both values of β with only a couple of points slightly outside the lower bound prediction. This, however, is also observed for the Master Curve. The comparison to the Master Curve is very good over the lower transition region before becoming slightly wider at higher temperatures. This provides confidence in the finite element analyses and developed local approach model. That the results widen at higher temperatures is likely to be an effect of plasticity which could manifest in both the accuracy of the finite element analyses and of the assumptions in the local approach model. The effect of changing β is only slight over the lower DBT transition region, where the higher value of β provides a narrower probability bound, as reflected in Fig. 2. Figure 3. Temperature dependence predicted by proposed model with β = 2.7 (left) and β = 4.0 (right) for the un-irradiated material. Experimental data and Master Curve predictions shown for comparison. Figure 4. Temperature dependence predicted by proposed model with β = 2.7 (left) and β = 4.0 (right) for the irradiated material (4.3 x 1019 n cm-2, En > 1 MeV at 285oC). The predictive bounds from the model for the irradiated material are given in Fig. 4, again with β =2.7 (left) and β =4 (right) carbide size distributions. It can be seen that both the developed model and the Master Curve profiles provide a good fit to the experimental data. It must be emphasised that our model’s predictions are based only on the changes in the tensile properties from the un-irradiated analyses while the calibrated model parameters were the same. At the same time the position of the Master Curve is dictated by the experimentally determined T0 for the irradiated state.
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