PSI - Issue 28

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L.A. Igumnov et al. / Procedia Structural Integrity 28 (2020) 2086–2098 L.A. Igumnov, I.A. V lkov/ Structural Integrity Procedia 00 (2019) 00–000

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Fig. 1. Experienced and fatigue calculated curves.

In the second example, the results of analyzing the processes of long-term strength of the VZh-159 heat-resistant alloy are presented. Fig. 2 depicts the creep curves for:  temperature 750 o T C  and stresses 11 350 MPa   и 450 М P а , respectively (Fig. 2a);  temperature 850 o T C  and stresses 11 120 MPa   and 150 М P а , respectively (Fig. 2b);  temperature 750 o T C  and a transition from stress level 11 350 MPa   to stress level - 11 450 MPa   (Fig. 2c);  temperature 850 o T C  and transition from stress level 11 120 MPa   to stress level – 11 150 MPa   (Fig. 2d). Here, the solid lines represent the results of numerical modeling, using the defining relations of MDM, and the dotted ones show the corresponding experimental results. The qualitative and quantitative agreement between the experimental and numerical results is evident.

Figs. 3–6, corresponding to the experiment depicted in Fig. 2d, show:  effective stresses 11   as a function of process duration t (Fig.3);  effective radius of zero level creep surface с С  as a function of t (Fig. 4);  creep failure energy с W as a function of process duration (Fig. 5);  damage degree  as a function of process duration t (Fig. 6).

The next example presents the results of numerically studying the carrying capacity of an NPP reactor vessel in the conditions of a hypothetical emergency according to the long-term strength mechanism. The material of the reactor vessel is steel 15H2NMFA. An axisymmetric reactor vessel consisting of a cylindrical sidewall with an elliptical bottom was used as an analytical model. The emergency situation was modelled by an effect of internal hydrostatic pressure p 1 , changing from zero at a height of h 1 . 5 m from the lowest point of the bottom and modelling a force effect from the meltdown, internal pressure p 2 , and temperature T varying within the analyzed part of the reactor vessel from 184 ◦ C to 1510 ◦ C.