PSI - Issue 6

Irina Stareva et al. / Procedia Structural Integrity 6 (2017) 48–55 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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stresses are equal to the maximum (in absolute value) stresses at the most strained cross-sections of the tubes with the lengths z l   200 m, correspondingly. The growth of the inner radii with time in these points is shown in Fig. 2, where (0) r is the inner radius at the initial time, 0 r . The lower indices at r indicate the z coordinate. Since the dependencies of the external radii on time are symmetrical to ( ) r t with respect to the line 0.91  r , they are not presented in Fig. 2. The point of stop is time to reach the residual thickness 6 10  m. The time step is taken 4 hours and the spatial step is 1 m. As one can see, a perceptible increase in the stresses is observed only for long enough tubes and only for the period when their residual thickness becomes rather small. This confirms once again that the use of stress criteria is not justified in such cases. Similar behaviour occurs for other corrosion kinetics constants (e.g., Kabanin et al. (2007)).

Fig. 1. The stresses over time.

Fig. 2. The inner radii over time.