PSI - Issue 13

M. Hrstka et al. / Procedia Structural Integrity 13 (2018) 1123–1128 Hrstka, M., Zˇ a´k, S., Vojtek, T. / Structural Integrity Procedia 00 (2018) 000–000

1128

6

between the monotonic and cyclic plastic zone for assessment of the SSY conditions and that the true ratio of sizes of the monotonic / cyclic plastic zones is much di ff erent from the common estimate.

6. Conclusion

The plastic zone sizes were found to be are very large under mode II and mode III loading even at the loading level corresponding to e ff ective threshold. It was explained by a low stress gradient under shear-mode loading and by a large ratio of sizes of the monotonic and the cyclic plastic zone which is di ff erent from the common estimate of 1 / 4. Relations (4) and (5) defining plastic zones by both Irwin’s and HRR solution are products of normalized shape functions and stress amplitude which is characterised by SIF or J-integral. Thus, plastic zone size depends on the behaviour of the amplitudes during loading. The plastic zone computed by FEM expands more in the axis of the crack at higher loading levels. The limited validity of the small scale yielding is obvious from Fig. 3 and Fig. 4.

Acknowledgements

This work was financially supported by the Czech Science Foundation (GA Cˇ R) in the frame of the Project No. 17-15716Y. Computational resources were supplied by the Ministry of Education, Youth and Sports of the Czech Re public under the Projects CESNET (Project No. LM2015042) and CERIT-Scientific Cloud (Project No. LM2015085) provided within the program Projects of Large Research, Development and Innovations Infrastructures.

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