PSI - Issue 42

Lucie Malíková et al. / Procedia Structural Integrity 42 (2022) 1082–1089 Lucie Malíková et al. / Structural Integrity Procedia 00 (2022) 000–000

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(a) (b) Fig. 4. Equivalent stress intensity factor range as a function of the relative crack length for various crack inclination angles (-45° to +45°) and corrosion pit of the length 2 P = 2 mm: (a) whole crack range investigated (between 0.1 and 4 mm), (b) short cracks (between 0.1 and 1 mm).

(a) (b) Fig. 5. Equivalent stress intensity factor range as a function of the relative crack length for various crack inclination angles (-45° to +45°) and corrosion pit of the length 2 P = 4 mm: (a) whole crack range investigated (between 0.1 and 4 mm), (b) short cracks (between 0.1 and 1 mm).

4.2. Dependence of the fatigue parameter  K eq on the initial crack inclination angle

When the curves of  K eq are compared for various initial crack inclination angles, the following statements can be introduced:  ESIFR for a perpendicular crack (  = 0) reaches the highest values in all configurations under study. This idea can be interpreted in the way that the perpendicular crack has the biggest potential for fatigue propagation.  Dependences of ESIFR obtained for the corresponding inclination angles (-45° and 45°, -35° and 35° etc.) are nearly identical for longer cracks (in dependence on the size of the corrosion pit).  When the crack is short, it is influenced by the presence of the corrosion pit. Namely, the larger is the crack inclination angle the larger is the difference between the results obtained for corresponding angles  (-45° and 45°, -35° and 35° etc.).  The largest difference can be observed for  = -45°, i.e. for a crack mostly inclined to the corrosion pit. Within this configuration, the corrosion pit has the largest effect on the crack propagation.  For all deflected cracks, the values of the ESFIR are lower than in the case of a perpendicular crack. Moreover, the lowest ones occur for the crack described above (  = -45°). Thus, it can be concluded that the corrosion pit tries to stop/slow down the crack propagation.