13th International Conference on Fracture June 16–21, 2013, Beijing, China As you can see for use of GTN-model it is necessary to identify seven parameters or six parameters if εN is assumed to be equal zero. Moreover in common case fc depends on stress triaxiality. It is increase number of constants. If the criterion (Eq. 6) is used we need to identify three constant, namely max vρ , σd and def nuc V (initial volume of deformation void). Of course, as for both criterion (Eq.6) and GTN-model function σS(æ) should be known. So it is clear that the use of criterion (Eq. 6) is much simpler than GTN-model. 3. Simulation of material fracture under different conditions of irradiation and testing The weld metal of 18Cr-10Ni-Ti steel in the initial and irradiated conditions was chosen as an object for the use of the model. Welding was performed with the use of 19Cr-11Ni-3Mo welding wire without subsequent heat treatment. Weld metal specimens were irradiated in the BOR-60 reactor by neutron doses in the range from 6-7 to 46 dpa at a temperature Тirr=320-340C [11]. As the criterion of fracture of a smooth cylindrical specimen the fracture of the central fibre of a specimen neck was taken. To describe the dependences characterizing SST in the central fibre of a specimen neck, eq m m σ σ q (æ) and eq 1 1 σ σ q (æ) the Bridgman’s formulas [12] were used. Over the range of Тtest=80-495°С the values of fracture strain calc fε were calculated on the basis of the condition (Eq. 6). Model parameters are assumed as temperature independent. Fig. 1a shows the experimental data and the dependence calc fε (Ttest). As input data generalized stress-strain curves (SSCs), calculated by equations presented in [11] were used. Values of model parameters are presented in [13, 14]. a) b) 0 200 400 Ttest, °C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 f 0 200 400 Ttest, °C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 f Figure 1. Temperature dependence of the fracture strain of material irradiated by the dose D=46 dpa at Tirr=330-340°C: - experimental data, (a) curve - calculated by the model with regard for generalized stress-strain curves [11]; (b) - points calculated by the model on the basis of individual SSC Additional calculations calc fε were performed for each temperature taking into accounts individual SSCs, obtained from test of each specimen. Results of performed calculations for each test temperature presented on the Fig. 1b. As is seen from Fig. 1, a good agreement between the experimental data and results calculated by the model is observed. The presented data shows that with invariant values of σd and max vρ the model makes correct predictions of the value exp fε at different Ttest especial with taking into account the peculiarities of individual stress-strain curves for -4-
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