PSI - Issue 7

G. Härkegård / Procedia Structural Integrity 7 (2017) 343–350 F / Structural Integrity Procedia 00 (2017) 000–000

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G. Härkegård 0

Fig. 4. Comparison between El Haddad and Murakami predictions for the fatigue limit of Cr steel with an embedded elliptical crack.

6. Conclusions

• Power-law equations for the fatigue limit of a cracked member, similar to models suggested by Frost and Murakami, may be identified with tangents to the El Haddad curve, with reasonable agreement for limited ranges of the crack size. • Frost predictions are in reasonable agreement with those by El Haddad for 0 a a = 0.5–10. • Murakami predictions are in reasonable agreement with those by El Haddad for 0 a a = 0.03–4. Appendix A. Stress-intensity factor for embedded elliptical crack A.1. General solution for the stress-intensity factor Consider first the elliptical crack depicted in Fig. A.1 with minor semi-axis a and major semi-axis c . The crack is embedded in an infinite solid subjected to a uniform tension σ perpendicular to the xz -plane.

Fig. A.1. Elliptical and circular cracks with equal areas.