PSI - Issue 42

Darko Pastorcic et al. / Procedia Structural Integrity 42 (2022) 374–381 Darko Pastorcic et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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3.4. Numerical results Using previously described material characterization and 3-D models of the corroded specimens, finite element analysis was conducted utilizing Ansys LS-Dyna program with SOLID 187 tetrahedral elements. The length scale parameter (  0.1mm) determines the size of the elements around the pits which generates huge number of elements and therefore submodelling was performed, Fig. 6.

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Fig. 6. Submodelling; 36 months exposure in the sea (a) HAZ and WM, (b) BM.

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Fig.7. Fracture initiation 36 months exposure BM: (a) sea slush, (b) sea.

The stress concentration occurs on the bottom of the pit, on the wall of the pit and on the ligament between the pits, what implies that pit distribution over the surface, therefore distance and diameter, influences decrease of the mechanical properties as well as the pit depth, which changes significantly within the first six months. Fig.8(a), (b), (c) present the relation of the equivalent plastic strain to the strain stress triaxiality for the first failure element in the BM for different environments and exposure times and Fig.8(d) same dependence for HAZ and WM after 36 months, while Fig. 7 presents ductile crack initiation.

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