PSI - Issue 21

Emre Kurt et al. / Procedia Structural Integrity 21 (2019) 21–30 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The initial crack dimensions given in Fig. 2 are crack depth, a=0.1 mm, crack length, c=0.15 mm and crack tilting angle , θ=30°. A uniform tensile stress, p=50 MPa is applied to the unit cube. The fatigue crack growth related material properties, C and n used in the analyses are 1.0·10 -22 (mm/cycle·(Pa·mm 0.5 )) and 2.0, respectively. Young’s modulus and Poisson’s ratio are E = 10 GPa and v = 0.3. In order to simplify the geometry and shorten the analysis time, the unit cube model is modeled ½ symmetrically and that hexahedral enriched and transition elements are used along and near the crack front, while remaining regions are meshed using tetrahedral elements (Fig. 3). 1 APR 5 2019 00:42:01 ELEMENTS 1 JUL 24 2018 13:49:24 ELEMENTS

Enriched Elements

Transition Elements

Z

Y

X

Fig. 3. The unit cube finite element model, the enriched and transition elements.

Fatigue crack growth analyses are performed and distributions of mixed mode three-dimensional SIFs along the crack front obtained for each incremental crack propagation steps using FCPAS are given in Fig. 4.

1.20

0.00 0.10 0.20 0.30 0.40

16th crack front

1.00

0.80

0.60

-0.50 -0.40 -0.30 -0.20 -0.10

0.40 K I (MPa·m½)

K II (MPa·m½)

Pre-crack

0.20

0.00

0 ° 20 ° 40 ° 60 ° 80 ° 100 °120 °140 °160 °180 °

0 ° 20 ° 40 ° 60 ° 80 ° 100 °120 °140 °160 °180 °

Angular position along crack front, θ

Angular position along crack front, θ

(a)

(b)

-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20

16th crack front

K III (MPa·m½)

Pre-crack

0 ° 20 ° 40 ° 60 ° 80 ° 100 °120 °140 °160 °180 °

Angular position along crack front, θ

(c)

Fig. 4. Distributions of mixed mode SIFs, a) K I , b) K II , c) K III , along the crack front for each crack propagation step.