PSI - Issue 7

B.M. Schönbauer et al. / Procedia Structural Integrity 7 (2017) 492–496 B.M. Schönbauer et Al./ Structural Integrity Procedia 00 (2017) 000–000

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main difference between defects that either do or do not exhibit non-propagating cracks at the fatigue limit is their notch root radius, ρ . Non-propagating cracks can be observed at defects with small but not with large notch root radius. Based on the experimental results, it might be concluded that the critical notch root radius, above which a defect cannot be treated as an equivalent crack (i.e., a fracture mechanics approach is not applicable), is ρ ≈ 50 µm under uniaxial loading and ρ ≈ 100 µm under torsional loading for the investigated 17-4PH stainless steel.

Fig. 5. Relationship between fatigue limit in defect size under uniaxial and torsional loading condition. Data from Schönbauer et al. (2017a); Schönbauer et al. (2017b); Schönbauer et al. (2017d)

Acknowledgements The financial support of the Austrian Science Fund (FWF) under project number P 29985-N36 is gratefully acknowledged. References Murakami, Y., Endo, M., 1986. Effect of hardness and crack geometries on DKth of small cracks emanating from small defect, in: Miller, K.J., de Los Rios, E.R. (Eds.), The Behavior of Short Fatigue Crack, Vol. EGF Pub. 1. Mechanical Engineering Publications, London, pp. 275-293. Schönbauer, B.M., Stanzl-Tschegg, S.E., Perlega, A., Salzman, R.N., Rieger, N.F., Turnbull, A., Zhou, S., Lukaszewicz, M., Gandy, D., 2015. The influence of corrosion pits on the fatigue life of 17-4PH steam turbine blade steel. Eng Fract Mech 147, 158-175. Schönbauer, B.M., Yanase, K., Endo, M., 2016. VHCF properties and fatigue limit prediction of precipitation hardened 17-4PH stainless steel. Int J Fatigue 88, 205-216. Schönbauer, B.M., Yanase, K., Endo, M., 2017a. The influence of various types of small defects on the fatigue limit of precipitation-hardened 17-4PH stainless steel. Theor Appl Fract Mech 87, 35-49. Schönbauer, B.M., Yanase, K., Endo, M., 2017b. Influences of small defects on torsional fatigue limit of 17-4PH stainless steel. Int J Fatigue 100, Part 2, 540-548. Schönbauer, B.M., Fitzka, M., Karr, U., Mayer, H., 2017c. Variable amplitude loading of 17-4PH stainless steel in the VHCF regime, in: Christ, H.-J., Zimmermann, M. (Eds.), VHCF7. H.-J. Christ, Dresden, Germany, pp. 237-242. Schönbauer, B.M., Mayer, H., Yanase, K., Endo, M., 2017d. Torsional fatigue properties of 17-4PH stainless steel in the VHCF regime, in: Christ, H.-J., Zimmermann, M. (Eds.), VHCF7. H.-J. Christ, Dresden, Germany, pp. 130-135.