PSI - Issue 13

Gyo Geun Youn et al. / Procedia Structural Integrity 13 (2018) 1297–1304 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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CF8A and Eq. 6 for aged CF8A. The same critical damage value, ω c =0.65 is applied for both unaged and aged CF8A. The prediction result is shown in Fig. 8. The results show that the prediction agrees well with the test.

Fig. 7. CF8A cyclic tensile test simulation result (a) unaged CF8A 0.87% strain amplitude (b) aged CF8A 1.20% strain amplitude

Fig. 8. Fracture toughness prediction of unaged and aged CF8A under monotonic and cyclic loading condition (a)unaged CF8A (b)aged CF8A

6. Conclusion

In this research, a simple method to predict cyclic loading effect for aged CF8A is suggested. For the prediction, a method to consider ageing effect is provided preferentially. To predict ageing effect, thermal ageing constant “ C ” is introduced under monotonic loading. After that, a method to consider cyclic loading effect is given. To predict cyclic loading effect, two assumptions are presented. The first one is about energy conservation and the second one is about crack opening state. Also, combined hardening model with third order nonlinear kinematic hardening model is adopted to simulate cyclic behavior. From the procedure, reasonable prediction results can be obtained. Acknowledgements This research was supported by National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning. (NRF-2017R1A2B2009759) References Peckner, D. and Bernstein, I. M., 1977, “Handbook of Stainless Steels,” McGraw-Hill, New York. Chung, H. M. and Chopra, O. K., 1987, “Kinetics and Mechanism of Thermal Aging Embrittlement of Duplex Stainless Steels,” Argonne National Lab ., IL, USA. Chung, H. M. and Leax, T. R., 1990, “Embrittlement of laboratory and reactor aged CF3, CF8, and CF8M duplex stainless steels,” Mat. Sci. Tech. , 6, 249–262.