PSI - Issue 42

712 Toru Yagi et al. / Procedia Structural Integrity 42 (2022) 702–713 Author name / Structural Integrity Procedia 00 (2019) 000 – 000 c . The damage index, equation (8), is used for evaluation of crack propagation. Fig. 4.1 is the crack surface model of FEM analysis. The width of LBZ is changeable. = 1 − { 0 max } { 1 − 1 − (− ( max − − )) 1 − − } (8) 11

Fig. 4.1 crack surface model of FEM analysis

4.2. Results With the model explained in section 4.1, the FEM analysis is conducted. The combination of the parameter shown in table 2 showed the closest result compared to the experimental result (Fig. 4.2). The non-blue area is where the crack propagates. The initial crack velocity is 1900 m/s which is natural compared to the previous studies. In this section, the possibility to express the pop-in crack by the FEM analysis incorporating the idea of energy dissipation is suggested. Table 2. Values of FEM analysis parameter c of LBZ [J/m 2 ] 1000 f of LBZ [MPa] 1200 c of Base Metal [J/m 2 ] 1500 f of Base Metal [MPa] 3000

Fig. 4.2 results of crack surface and crack veloxity