PSI - Issue 5

A. Eremin et al. / Procedia Structural Integrity 5 (2017) 889–895 A. Eremin et al / Structural Integrity Procedia 00 (2017) 000 – 000

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The single overload cycle initiates crack blunting and gives rise to increasing the near-tip residual compressive stresses. The latter are kept even after 2 000 cycles when the crack has already propagated by 14 % towards the overload plastic zone. This results in sharp growth of the ε max parameter till 100 cycles and after extension of crack into the plastic zone by a few microns. Subsequent cyclic loading gives rise to further crack propagation which should reduce near-tip residual s tresses. It is the reason why the crack opening displacement (ε max ) is decreased. However, the ε max value did not reduced even after crack length increment exceeding 100 µm. Further prospects of the study are related to computation of crack opening/closure levels and estimation of near-tip stresses as well as searching for other reliable parameters which can characterize the changes in hysteresis loop shape.

Acknowledgements

The work was performed in the framework of fundamental research projects of the Russian State Academies of Sciences (2013 – 2020), and with a partial support of RFBR Grant No. 15-08-05818_a and Grant No. 11.2 of the Russian Academy of Sciences (Department of Power Engineering, Mechanical Engineering, Mechanics, and Control Processes).

References

Wohler, A., 1870, Uber die Festigkeits – Versuche mit Eisen und Stahl [On strength tests of iron and steel]. Z. Bauwesen 20, pp. 73 – 106. Basquin, O. H., 1910, The exponential law of endurance tests. Proceedings - American Society for Testing Materials 102, pp. 625 – 639. Paris, P. and Erdogan, F., 1963, A critical analysis of crack propagation laws. Journal of Basic Engineering 90, pp. 528 – 534. Elber,W., 1970, Fatigue crack closure under cyclic tension. Engineering Fracture Mechanics 21, pp. 37 – 45. Newman, J. C. ,1981, A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading. NASA Technical Memorandum 81941, pp. 1743 – 1751. Newman, J. C., 1984, A crack opening stress equation for fatigue crack growth. International Journal of Fatigue 24, pp. 131 – 135. Sunder, R., 2015, Characterization of threshold stress intensity as a function of near – tip residual stress, Materials Performance and Characterization 4/2, pp. 105 – 130. Sunder, R., Andronik, A., Biakov, A., Eremin, A., Panin, S., Savkin, A., 2016, Combined action of crack closure and residual stress under periodic overloads: A fractographic analysis, International Journal of Fatigue 82, pp. 667 – 675. Sunder, R., Biakov, A., Eremin, A., Panin, S., 2016, Synergy of crack closure, near-tip residual stress and crack-tip blunting in crack growth under periodic overloads – A fractographic study, International Journal of Fatigue 93, pp. 18 – 29.