PSI - Issue 14

A.N. Savkin et al. / Procedia Structural Integrity 14 (2019) 684–687 Author name / Structural Integrity Procedia 00 (2018) 000–000

687

4

  

    σ σ σ 1 exp ε γ α ψ * p          n i i i i            E C

σ α tr     tr

f

1

n



(9)

     ε * b

 0 

0 y

0 y

y

p

n

Equation (9) can be solved iteratively using Newton–Raphson method until convergence condition is achieved.

Fig. 1. Graphical interpretation of the proposed procedure for determining near-tip stresses under various loading sequences: underload – overload (a); overload – underload (b)

3. Results and conclusion The calculated results obtained by new model are qualitatively and quantitatively similar to the same obtained with the traditional approach based on Neuber rule and Ramberg–Osgood stress strain relation. Further algorithm enhancement will be towards the research of more realistic rule for obtaining strain increment and extending to the elevated temperature for creep resistant superalloys, including consideration of more difficult stress states.

Acknowledgements

This paper was financially supported by the RFBR grant 17-08-01648 A, № 17-08-01742 A and the President of the Russian Federation grant MK-943.2017.8. References Sunder, R. 2005, "Fatigue as a process of cyclic brittle microfracture", Fatigue and Fracture of Engineering Materials and Structures, vol. 28, no. 3, pp. 289-300. Sunder, R. 2012, "Unraveling the science of variable amplitude fatigue", ASTM Special Technical Publication, pp. 20. Sunder, R. 2007, "A unified model of fatigue kinetics based on crack driving force and material resistance", International Journal of Fatigue, vol. 29, no. 9-11, pp. 1681-1696.