PSI - Issue 35

Vera Friederici et al. / Procedia Structural Integrity 35 (2022) 106–114 V. Friederici et. al / Structural Integrity Procedia 00 (2019) 000–000

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Figure 3a shows additionally the effect of corrosion on the core condition specimens. The SN-curves of the corroded samples are shifted downward in comparison to the non-corroded condition. Corrosion leads to a significant reduction in fatigue strength and fatigue life. Especially in the area of fatigue strength, corrosion has a decisive influence.

Fig. 3. SN-curves from core condition specimens with and without different pre-corrosion (a). CAE-Model of rotation-bending specimen with indicated crack plane and below a projection of several crack fronts onto the fracture plane for different steps of the calculation (b). The simulation was carried out for different loadings. Starting with a surface crack that extends 0.5 mm into the specimen surface, the simulation to determine the K IC values at the crack front is performed in iterative steps with a crack growth interval da of 0.1 mm. The resulting crack front lines for different steps of the crack propagation are visualized on the lower part of Figure 3b in the plane of the crack.

Fig. 4. From the total fatigue life curve (rotation-bending tests on core condition specimen) the crack propagation curve obtained from the FE simulation must be subtracted to calculate the crack initiation curve.