PSI - Issue 19

Kim Bergner et al. / Procedia Structural Integrity 19 (2019) 140–149 Author name / Structural Int grity Procedia 00 (2019) 000 – 000

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= , + , = ′ ∙ (2 ∙ ) + ′ ∙ (2 ∙ )

(2)

2.5. Results of the load-controlled fatigue tests

Fig. 5. Determined S-N curves of EN-GJS-400-15 with a pearlitic (blue) and ferritic (red) matrix in the rim zone

Fig. 6. Comparison of S-N curves of EN-GJS-400-15 specimens being completely machined, with surface roughness as well as with surface roughness and a pearlitic or a ferritic matrix The influence of the microstructure surrounding the lamellar graphite in the rim zone was determined with GE_I (pearlitic microstructure) and GE_II (ferritic microstructure) bending specimens. The internal notch effect of the lamellar graphite covers the influence of the surrounding microstructure on fatigue strength, which can be deduced from the quite similar S-N curve parameters of GE_I (σ a,n,k,50% = 114 MPa ) and GE_II (σ a,n,k,50% = 111 MPa), Fig. 5 and Table 3. Since the microstructure in the rim zone has a minor influence on fatigue strength, the results of the fatigue investigations of the bending specimens from GE_I and GE_II were evaluated together (Fig. 5). The results of the