Issue 51

F. Frabbrocino et alii, Frattura ed Integrità Strutturale, 51 (2020) 410-422; DOI: 10.3221/IGF-ESIS.51.30 420 In Fig. 12b, the initial mesh configuration used for the simulation is reported. As shown, a refined mesh discretization is considered just around the crack tip region, whereas the remaining part of the structure requires a relatively coarse mesh. Fig.13a represents the dynamic stress intensity factor time history detected by the proposed formulation. Fig. 13b shows the crack tip speed time history components along X (blue) and Y (red), whereas crack tip speed (black) is computed as 2 2 X Y c c c   . In Fig. 14, Von Mises stress maps, coincident at several times selected at magenta points of Fig. 13 (from A to F), are reported. The analysis shows that the crack initiation angle is equal to 33° and it remains substantially unaltered during the whole propagation process. It is worth noting that the proposed procedure is strictly dependent from internal parameters, such as the limit value of angle tolerance, which may influence the solution in terms of both computation efforts and accuracy. A detailed discussion about this aspect is reported in [19]. It is worth noting that such parameter controls the maximum variation angle allowed during the crack growth and in this case is set equal to 2°. Once that the predicted crack propagation angle is larger than the tolerance value, a re-meshing procedure is required. This procedure, extensively described in a previous authors’ work developed in static framework [27], is made by proper script files implemented in a MATLAB® environment, which manages the numerical procedure. Figure 13 : (a) Variation of dynamic stress intensity factor vs time; (b) Crack tip speed components time history. Figure 14 : Von Mises stress maps at six crack propagation steps (from point A to point F, shown in Fig. 13a). C ONCLUSIONS ynamic crack propagation phenomena are successfully simulated by using a new numerical methodology, which combines concepts arising from solid mechanics, fracture mechanics and moving mesh methodology. The numerical formulation is able to describe crack propagation just by adopting a proper crack function and kinking D