PSI - Issue 39

Georg Schnalzger et al. / Procedia Structural Integrity 39 (2022) 313–326 Author name / Structural Integrity Procedia 00 (2019) 000–000

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9

Table 3. Details for the experiments with undeformed and pre-deformed R260.

undeformed state

pre-deformed state

shear pre-deformation γ [-]

0

3.5

external specimen diameter [mm]

20

17

notch geometry pre-fatigue mode

notch A

notch B

tension-tension (R = 0.1)

compression-compression (R = 17)

load cycles without bifurcation [-]

30,000

58,000

Δ τ max [MPa] 2 a coplanar [µm]

147 126

74

front: 184, back: 253

The micrographs in Fig. 9 present the macroscopic crack paths occurred in the undeformed and pre-deformed R260. Colored arrows indicate the contribution of different crack propagation phases, i.e., Mode-I pre-fatigue, Mode-II dominated coplanar FCG and bifurcation.

Fig. 9. Crack path including different crack growth phases: (a) undeformed ( γ = 0) and (b) pre-deformed ( γ ~3.5) R260.