PSI - Issue 24

Alessandro Castriota et al. / Procedia Structural Integrity 24 (2019) 279–288 A. Castriota et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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(a)

(b)

Fig. 9. Numerical results: (a) comparison of the normalized deformations for some points of the intact and damaged panel; (b) comparison normalized load – displacement curves

two configurations considered; how it was expected, the intact panel showed lower deformations than the damaged panel, even if the difference is not particularly high. Also the global stiffness of the panel showed the same behavior (Fig. 9b). A variation of 9% stiffness of the panel with saw-cut compared to the intact panel was evaluated (Table 1).

Table 1. Numerical axial normalized stiffness

Numerical test case Panel without saw-cut Panel with saw-cut Percentage change

Normalized k axial

18.852 17.157

-9%

A further calculation concerned the numerical determination of the first load and the first buckling mode in the two cases examined. Also in this case, the intact panel has a higher buckling load than in the case of the panel with saw-cut; this is evident from the value of the first eigenvalue obtained from the calculation, as shown in Table 2. In this case, the percentage variation of the buckling load between the two cases is equal to -3.51% with respect to the buckling load of the intact panel.

Table 2. First eigenvalue for numerical cases

λ

Numerical test case Panel without saw-cut Panel with saw-cut Percentage change

2.4260 2.3407 -3.51%

Fig. 10 shows the buckling mode for the two cases considered. It can be seen that the presence of the cut reduces the buckling resistance and produces a large involvement of the rib closer to the load side. Moreover, the associated buckling mode changes from the anti-symmetrical (Fig. 10a) to symmetrical (Fig. 10b).