PSI - Issue 39

R. Yarullin et al. / Procedia Structural Integrity 39 (2022) 364–378 Author name / S ructural Integrity Procedia 00 (2021) 00 –000

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Fig. 6. (a) Halfway crack shape (before front separation); (b) final crack shape (after front separation) with definition.

3.2. Numerical simulation algorithm Numerical simulations were performed by the synergic use of the software ABAQUS and FRANC3D. The specimen was modelled by ABAQUS software. The FEM model includes the material parameters, the boundary conditions and the initial, uncracked mesh; this is the input for FRANC3D software. Here, the uncracked FEM model is subdivided into two regions: the global and the local. The latter is known as domain , i.e. the part of the mesh where crack propagation is supposed to take place. This is a convenient choice for fracture simulations since it allows to identify a reduced remeshing volume and, therefore, to speed-up the analysis (Giannella et al. 2019, Giannella and Perrella 2019, Giannella 2021, Giannella et al. 2019). Each simulation step consists of three phases: during the pre processor phase, the new crack is geometrically inserted into the domain and it is remeshed with quadratic tetrahedral elements; then, the local and the outer global mesh are merged together. The second phase is the FE calculation, during which stress and displacement components are calculated for all nodes. The post-processor phase aims to determine the SIFs for each crack front(s) nodes and to extend them towards their propagation direction. Fig. 7 reports a scheme of the procedure needed to complete one propagation step.

Fig. 7. Numerical simulation algorithm scheme.