PSI - Issue 39

Aljaž Ignatijev et al. / Procedia Structural Integrity 39 (2022) 89 – 97 Author name / Structural Integrity Procedi 00 (2019) 000– 00

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Fig. 3. Von Mises equivalent stress: (a) Model 1, (b) Model 2 and (c) Comparison of the results.

2.3. Fatigue crack initiation period The fatigue material properties of used sintered steel were taken from the previous work by Šori (2016), in which the static material parameters, the fatigue strength coefficient and the fatigue strength exponent were reported. The cyclic strength parameters were determined on the basis of the Ramberg-Osgood equation. Because of relative high stresses which exceeded the yield stress of the material, the strain-life approach was used in the computational model. The fatigue ductility coefficient ε f ' and the fatigue ductility exponent c were determined with eqs. (1) and (2) from literature by Glodež (2006) . Table 3 shows the needed material parameters which were used in the subsequent computational analyses. The results of the fatigue crack initiation period for load case 3 are shown in Fig. 4. = ′ (1) ′ = � ′ ′ � (2) Table 3. Fatigue material properties of Cu–Ni–Mo sintered steel in hardened states. Parameter Symbol Value Cyclic strength coefficient K’ [MPa] 1,154 Cyclic strength hardening exponent n ’ [−] 0.199 Fatigue strength coefficient σ f ’ [MPa] 875 Fatigue strength exponent b [−] -0.153 Fatigue ductility coefficient ε f ’ [−] 0.249 Fatigue ductility exponent c [−] -0.769