PSI - Issue 18

Tintu David Joy et al. / Procedia Structural Integrity 18 (2019) 287–292 T. D. Joy, G. Kullmer / Structural Integrity Procedia 00 (2019) 000–000

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Table 1. Material Data used for simulation and for calculating crack initiation lifetime. Young's modulus Poisson’s ratio R-ratio Fatigue strength coefficient

Fatigue ductility coefficient

Fatigue strength exponent

Fatigue ductility exponent

70656 -0.806 Fig. 3 a shows the input model created in A BAQUS . The FE-Model was generated from A BAQUS with linear tetrahedral elements and the model was simulated in A DAPCRACK 3D to automatically initiate a crack. Fig. 3 b shows the maximum principal stresses obtained after simulating the model in A BAQUS . 0.34 -1 1231 0.263 -0.122

Fig. 3. (a) Input model for A DAPCRACK 3D; (b) Stress distribution after the A BAQUS simulation; (c) Automatically initiated technical crack.

The region marked in Fig. 3 b is the position where the maximum principal stresses are the highest. A DAPCRACK 3D selects the node where the maximum principal stress is at its highest value for the crack initiation. If required the stress gradients are also calculated for the nodes in this region. The crack initiation direction and plane are calculated from the stress tensor of the selected node. Fig. 3 c shows the automatically initiated crack in A DAPCRACK 3D and the load cycles calculated for initiating this crack are 9.6E+06. Automatic crack initiation in A DAPCRACK 3D was also tested with more specimens: 3 point bending specimen, compact-tension specimen (CT) and arc-shaped specimen. The results obtained for the compact-tension specimen and the arc-shaped specimen are shown in Fig. 4.

Fig. 4. (a) Stress distribution in CT-Specimen, automatically initiated crack; (b) Stress distribution in arc-shaped Specimen, automatically initiated crack.