PSI - Issue 39

145 7

Deborah Weiß et al. / Procedia Structural Integrity 39 (2022) 139–147 Author name / Structural Int grity Procedia 00 (2019) 000–000

a

b

80

α = 45 °

φ 0 = 38 °

60

40 kinking angle φ 0 [°]

c

Residual forced fracture

α = 15° α = 90° α = 75° α = 60° α = 45° α = 30°

Fatigue crack

20

Experiment MTS-criterion

0

0

0,25

0,5

0,75

1

Mode Ⅰ pre-crack

K II /(K I +K II )

Fig. 4. (a) Comparison of the experimentally determined kinking angles (orange) with the theoretically determined kinking angles according to the MTS-criterion (grey line); (b) microscopy of a kinking angle ϕ 0 under a loading angle of α = 45°; (c) fracture surfaces of various loading angles α .

Test method cyclic-test Material HCT590X – 1.5 mm F max = const. 2.5 kN R -ratio 0.1 Test frequency 20 Hz Specimen shape modified CTS-specimen

1,E-09 1,E-08 1,E-07 1,E-06 1,E-05 1,E-04 1,E-03 1,E-02 1,E-01 1,E+00

α = 0° α = 45° α = 90°

crack growth rate [mm/Lw]

40 45 50 55 60 65 70 75 80

crack length [mm]

initiation of a pre-crack under 0° loading

Fig. 5. Influence of different loading angles α on the crack growth rate. Fig. 4c displays fracture surfaces of the different loading angles α = 0°, α = 15°, α = 30°, α = 45°, α = 60°, α = 75° and α = 90°. The Mode I pre-crack, the fatigue crack at different loading angles α and the residual forced fracture that was induced again under a loading angle α = 0° are illustrated.