PSI - Issue 13

Gyo Geun Youn et al. / Procedia Structural Integrity 13 (2018) 1305–1311 Auth r name / Struc ural Integrity Procedia 00 (2018) 000 – 00

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Fig. 7. Dimensions of the pipe system used for virtual test

4.2. Crack growth prediction for virtual piping system test The FE model applied for the analysis is given in Fig. 8. For the elbow section and crack section, 3-D first order element with incompatible mode (C3D8I in ABAQUS) is used. Pipe element (PIPE31 in ABAQUS) is used for straight pipe section. For the crack section, through-wall crack of 43.2 o and 90 o are considered as shown in Fig. 8. Combined hardening model is applied to simulated the cyclic behavior. The determined cyclic material properties are given in Youn et al. The load is applied by displacement at a point shown in Fig. 8 and the input displacement is given in Fig. 9.

Fig. 8. FE model used for pipe system analysis

Fig. 9. Input displacement for the pipe system test

For the virtual pipe system test, multi-axial fracture strain energy model is applied. The multi-axial fracture strain energy, W f is given in Eq. 6. Also the critical damage value, ω c is 0.35. By applying the multi-axial fracture strain energy model, the crack growth behavior of the pipe system is predicted as Fig. 10. From the result, it can be known that the crack growth of unaged and aged CF8A do not show much difference at through-wall crack size of 43.2 o . However, the crack growth of aged CF8A is larger than unaged CF8A when the size of through-wall crack is 90 o .