13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- (2) Other surfaces satisfy: െKడ డ் ൌ0. The used boundary conditions to determine the mechanical field are as follows (1) Fixed boundary condition is applied to the side surface, shown as Fig.1 (2) The unseen lower surface and the front surface are set as free boundaries. (3) Other surfaces are applied with symmetric boundary conditions. 4. Results and discussion In this section, the effectiveness of the irradiation hardening simulation is validated, and the obtained temperature field and mechanical ones are to be shown and discussed. 4.1. Validation of irradiation hardening simulation In order to make the correctness of irradiation hardening simulation confirmed, node M in the cladding is selected and the calculated Mises stresses and equivalent elasto-plastic strains at different time have been output. Taking them as the longitudinal and transverse ordinates respectively, three points can be produced in Fig.3. Meanwhile the irradiation hardening curves of the cladding material at the corresponding irradiation damage and temperature are plotted in Fig.3. It can be seen that the obtained computation results obey the irradiation hardening curves, which denotes that the irradiation hardening effect is correctly simulated. 0.0 0.2 0.4 0.6 -100 0 100 200 300 400 500 600 700 Ture stress(MPa) (Ture elasto-plastic strain) 58.3days 115.5days 144.1days real results (a) (b) Figure.2 (a) The stress-strain curves and the numerical results of (b) node M in the cladding 4.2. The temperature results The calculated temperature field under heterogeneous irradiation condition is depicted in Fig.3 (a). It can be observed that the highest temperature with the red color locates in the fuel meat, precisely speaking, in the middle location along both the length and thickness directions. These phenomena result from the higher heat generation rate there. Thus, two paths in Fig.3 (b) are chosen to output the calculated temperatures at different time. The results under the uniform irradiation condition in Fig.4 are unchanged along the length direction of fuel plate. However, the temperature distribution under non-homogeneous conditions is approximately linear along the two paths, which is closely related to the heat generation rate of fuel meat. From 1.1 days to 144.1 days, the temperature
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