13th International Conference on Fracture June 16–21, 2013, Beijing, China each Ttest. Thus the effect of Ttest on εf is basically determined by the influence of strain hardening on the realization condition of a plastic collapse of a unit cell. For analysis of swelling effect and verification of model the weld metal specimens irradiated by a dose of 49 dpa at Тirr=400-450°С [15] were used. Swelling of these specimens varies from 3 up to 7%. Numerical simulation of the influence of vacancy void volume fraction on fracture strain is based on the following propositions: (1) the SSC for a material matrix, i.e. material without vacancy and deformation voids is invariant to swelling and irradiation temperature and depends only on a neutron dose and test temperature; (2) when calculating fracture strain for each temperature the individual values of swelling for each specimen [15] were used; (3) values of the parameters σd and max vρ are determined from the equality condition exp fε = calc fε at Тirr=320-340°С (i.e. without swelling [11, 15]) and Тtest=80°С, i.e. the same way as described for analyzing of test temperature effect. The results of the calculation of fracture strain in the absence and existence of swelling are shown in Fig. 2. It is seen from the figure that there is a close coincidence of the experimental and calculated data for specimens without and with swelling (for specimens without swelling comparison of exp fε and calc fε was shown above in Fig. 1). The obtained results suggest that a decrease of εf at Тirr=400-450°С compared with εf at Тirr=320-340°С is connected exclusively with vacancy void volume fraction that determines material radiation swelling. It should be noted that nonmonotonic of the dependence exp fε (Ttest) at Тirr =400-450°С is evidently determined by the inhomogeneity of specimens swelling. At the same time the average value of fracture strain fε over a temperature range of 80-425°С obtained experimentally approaches the calculated value: exp fε =0.26, calc fε =0.25. 0 100 200 300 400 T , °C test 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 f 6,8 6,4 3,4 4,0 Figure 2. Temperature dependences exp fε and calc fε for weld metal with and without swelling; the digitals denote swelling of specimens as a percentage: - fracture strain of weld metal without swelling (experiment); - fracture strain of weld metal with swelling (experiment); - calculated value of fracture strain of weld metal with swelling; –– –– –– - calculated temperature dependence of fracture strain of weld metal without swelling. 4. Analysis of an irradiation effect on fracture toughness To estimate the influence of SST in the dependence εf(D) let us compare the dependence 0 f f ε ε (D) -5-
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