## 4 Results and Discussion
Figure 9: FEM-DIC comparison using Ansys Mechanical APDL for Driemeier Pos30, Ti6 Al4V. Figure 11: FEM-DIC comparison using Ansys Workbench for Mohr15, Ti6 Al4V. Figure 12: FEM-DIC comparison using Ansys Mechanical APDL for Driemeier Pos10, 17-4 PH. Figure 10: FEM-DIC comparison using Ansys Workbench for Mohr00, Ti6 Al4V. Figure 14: FEM-DIC comparison using Ansys Workbench for Mohr00, 17-4 PH. Figure 13: FEM-DIC comparison using Ansys Mechanical APDL for Driemeier Pos30, 17-4 PH. Figure 15: FEM-DIC comparison using Ansys Workbench for Mohr15, 17-4 PH. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Ti6 Al4V**} & \multicolumn{4}{c}{**17-4 PH**} \\ \hline
**Test** & \(T_{avg}\) & \(X_{avg}\) & \(\varepsilon_{f}\)**[m/m]** & \(T_{avg}\) & \(X_{avg}\) & \(\varepsilon_{f}\)**[m/m]** \\ \hline Pos10 & 0.05 & 0.18 & 0.28 & 0.05 & 0.16 & 0.35 \\ Pos30 & 0.10 & 0.39 & 0.30 & 0.10 & 0.38 & 0.46 \\ Mohr00 & 0.02 & 0.07 & 0.16 & 0.03 & 0.14 & 0.35 \\ Mohr15 & 0.08 & 0.36 & 0.15 & 0.11 & 0.49 & 0.28 \\ RB & 0.48 & 0.99 & 0.63 & 0.61 & 0.99 & 1.17 \\ RNB & 0.72 & 0.99 & 0.36 & 0.76 & 0.99 & 0.81 \\ PS & 0.64 & 0.00 & 0.27 & 0.70 & 0.00 & 0.36 \\ Tors & 0.00 & 0.00 & 0.47 & 0.00 & 0.00 & 0.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average value of triaxiality and deviatoric parameter corresponding to plastic strain at failure in the critical area of all specimens, from FEM. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Ti6 Al4V**} & \multicolumn{4}{c}{**17-4 PH**} \\ \hline  & **Pos10** & **Pos30** & **Mohr00** & **Mohr15** & **Pos10** & **Pos30** & **Mohr0** & **Mohr15** \\ \hline Std. dev. \(T\) (\(\pm\)) & 0.01 & 0.02 & 0.01 & 0.02 & 0.01 & 0.02 & 0.01 & 0.03 \\ Std. dev. \(X\) (\(\pm\)) & 0.05 & 0.07 & 0.04 & 0.10 & 0.05 & 0.08 & 0.06 & 0.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Standard deviation (Std. dev.) of \(T\) and \(X\) with respect to the chosen average value \(T_{avg}\) and \(X_{avg}\). Figure 16: Evolution of triaxiality \(T\) with respect to equivalent plastic strain. The MMC, CC, and HC damage models were calibrated for Ti6 Al4V and 17-4 PH using data from Table 1, based on the combinations of tests indicated previously. More in detail, the first calibration is performed using only the experimental points of the conventional specimens (RB, RNB, Tors, and PS) and the resulting fracture surface was taken as a reference. The second and third calibrations involved the conventional RB and RNB specimens combined with the [PERSON] and [PERSON]'s multiaxial specimens, respectively. The fourth calibration involved the RB and RNB specimens along with all shear-tension specimens. Finally, in the fifth calibration, data from all experimental tests were used. To be brief, only the fracture surfaces for Ti6A4V and relative to the three damage models calibrated using the [PERSON] and [PERSON]'s specimens are reported in Figures 18-20. In particular, the [PERSON]'s fracture surface is shown in Figure 18a, Figure 19a, and Figure 20a, while the [PERSON]'s fracture surface is shown in Figure 18c, Figure 19c, and Figure 20c. In addition to the 3D graphs, 2D views of \(\varepsilon_{f}\) behaviour as a function of \(T_{avg}\) for curves at different \(X_{avg}\) are reported in Figure 18b,d, Figure 19b,d, and Figure 20b,d. For completeness, the points related to PS and Tors tests are also included in the graphs, to observe the proximity of the fracture surface to the fracture points relative to the conventional tests. The 3D and 2D views of the fractures surface show a good match with the experimental points employed as input in the minimization algorithm (Equation (9)), showing that each model formulation is well capable of capturing all experimental evidence. Figure 17: Evolution of deviatoric parameter \(X\) with respect to equivalent plastic strain.